JP2004355024A - Apparatus including virtually imaged phase array (vipa) in combination with wavelength splitter to demultiplex wavelength division multiplexed (wdm) light - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a large bandwidth, high resolution wavelength demultiplexer. <P>SOLUTION: Generally, a VIPA is a device which receives an input light having a respective wavelength within a continuous range of wavelengths, and causes multiple reflection of the input light to produce self-interference and thereby form an output light. The output light is spatially distinguishable from an output light formed for an input light having any other wavelength within the continuous range of wavelengths. The apparatus combines the VIPA with a demultiplexer, such as a diffraction grating. More specifically, the VIPA receives an input light and produces a corresponding output light propagating away from the VIPA. The output light includes a plurality of different wavelength components. The demultiplexer demultiplexes the output light into a plurality of separated lights corresponding, respectively, to the plurality of different wavelength components in the output light. Preferably, the demultiplexer has a dispersion direction which is substantially perpendicular to the dispersion direction of the VIPA. In this case, the separated lights from the demultiplexer can be detected with fibers arranged in a grid pattern. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an apparatus that includes a virtual image phase array (VIPA) for splitting wavelength division multiplexed (WDM) light. More specifically, the present invention combines wavelength-division multiplexed light with a relatively large number of closely separated wavelength components with a wavelength demultiplexer, such as a diffraction grating, that can be accurately demultiplexed. Related to a device that includes VIPA.

  Wavelength division multiplexing is used in optical fiber communication systems that transfer relatively large amounts of data at high speed. More specifically, a plurality of carriers modulated by the respective information are multiplexed into the wavelength division multiplexed light. The wavelength division multiplexed light is transmitted to a light receiver via one optical fiber. The light receiver divides the wavelength division multiplexed light into individual carriers and detects the individual carriers. Thus, a communication system can transfer a relatively large amount of data over an optical fiber.

  Therefore, the ability of the optical receiver to accurately split the wavelength division multiplexed light greatly affects the performance of the communication system. For example, even if a large number of carriers can be coupled to wavelength division multiplexed light, such wavelength division multiplexed light cannot be transmitted unless the receiver can accurately separate the wavelength division multiplexed light. . Therefore, it is desired that the optical receiver include a high-precision wavelength demultiplexer.

  FIG. 19 is a diagram illustrating a conventional filter using a multilayer interference film used as a wavelength demultiplexer. According to FIG. 19, a multilayer interference film 20 is formed on a transparent substrate 22. Light 24 is a collimated light, but is incident on film 20 and is subsequently repeatedly reflected within film 20. Due to the optical conditions determined by the characteristics of the film 20, only the light 26 having the wavelength λ2 is transmitted. Light 28, including all light that does not meet optical conditions, cannot pass through film 20 and is reflected. Thus, the filter shown in FIG. 19 is useful for demultiplexing wavelength division multiplexed light including only two carriers having different wavelengths of λ1 and λ2. However, such a filter has a problem that it cannot separate wavelength division multiplexed light having three or more carriers by itself.

  FIG. 20 is a diagram showing a conventional Fabry-Perot interferometer used as a wavelength demultiplexer. As shown in FIG. 20, the high reflectance reflection films 32 are parallel to each other. The light 34 is parallel light, is incident on the reflection film 30, and is reflected between the reflection films 30 and 32 many times. Light 36 of wavelength λ2 that satisfies the transmission conditions determined by the characteristics of the Fabry-Perot interferometer passes through the reflective film 32. The light 38 having the wavelength λ1 is reflected because it does not satisfy the passing condition. Thus, light having two different wavelengths is split into two different lights, each corresponding to two different wavelengths. Therefore, like the filter shown in FIG. 19, the conventional Fabry-Perot interferometer is useful for separating a wavelength division multiplexed light including only two carriers of different wavelengths λ1 and λ2. However, such a Fabry-Perot interferometer has a problem that wavelength division multiplexed light having three or more carriers cannot be separated.

FIG. 21 is a diagram showing a configuration of a conventional Michelson interferometer used as a wavelength demultiplexer. As shown in FIG. 21, the parallel light 40 enters the half mirror 42 and is split into a first light 44 and a second light 46 which are perpendicular to each other. The reflecting mirror 48 reflects the first light 44, and the reflecting mirror 50 reflects the second light 46. The distance between the half mirror 42 and the reflection mirror 48 and the distance between the half mirror 42 and the reflection mirror 50 indicate an optical path difference. The light reflected by the reflection mirror 48 returns to the half mirror 42, and interferes with the light reflected by the reflection mirror 50 and returned to the half mirror 42. As a result, the light 52 and the light 54 having the wavelengths λ1 and λ2, respectively, are separated from each other. Like the filter shown in FIG. 19 and the Fabry-Perot interferometer shown in FIG. 20, the Michelson interferometer shown in FIG. 21 separates wavelength division multiplexed light containing only two carriers of different wavelengths λ1 and λ2. Useful. Therefore, there is a problem that such a Michelson interferometer cannot separate a wavelength division multiplexed light having three or more carriers.

  It is possible to combine multiple filters, ie, Fabry-Perot or Michelson interferometers, into a large array so that other wavelength carriers can be separated from one wavelength division multiplexed light. However, such an arrangement has been problematic in that it is expensive, inefficient, and the receiver is undesirably large.

Diffraction gratings or arrayed waveguide gratings are often used to separate wavelength division multiplexed light consisting of two or more different wavelength carriers.
FIG. 22 is a configuration diagram of a conventional diffraction grating for dividing wavelength division multiplexed light. As shown in FIG. 22, the diffraction grating 56 has a grating surface 58. Parallel light 60 having a plurality of different wavelength carriers is incident on the grating surface 58. Different wavelength carriers are reflected at each step of the grating surface 58 and interfere with each other. As a result, carriers 62, 64 and 66 having different wavelengths are output from diffraction grating 56 at different angles and are therefore separated from one another.

  However, diffraction gratings output different wavelength carriers at relatively small dispersion angles. As a result, there is a problem that it is difficult for the light receiving device to accurately receive various carrier signals separated by the diffraction grating. This problem was particularly severe in a diffraction grating that splits wavelength division multiplexed light having a large number of carriers having relatively close wavelengths. In this case, the angular dispersion obtained by the diffraction grating was extremely small, typically about 0.05 degrees / nm.

  Further, the diffraction grating is affected by the polarization of the input light. Therefore, there is a problem that the polarization of the input light affects the performance of the diffraction grating. Further, there is a problem that the grating surface of the diffraction grating requires a complicated manufacturing process in order to generate an accurate diffraction grating.

  FIG. 23 is a diagram showing a configuration of a conventional arrayed waveguide grating for demultiplexing wavelength division multiplexed light. As shown in FIG. 23, light composed of a plurality of different wavelength carriers is received through an entrance 68 and split through a number of waveguides 70. A light outlet 72 is at the end of each waveguide 70 so that output light 74 is generated. The waveguides 70 have different lengths from each other, thus providing optical paths of different lengths. Thus, the light passing through the waveguide 70 has a different phase from each other and therefore interferes with each other when output through the outlet 72. This interference causes light having different wavelengths to be output in different directions.

  In an arrayed waveguide grating, the dispersion angle can be adjusted within a certain range by appropriately configuring the waveguide. However, arrayed waveguide gratings are affected by temperature changes and other environmental factors. Therefore, there has been a problem that it is difficult to appropriately adjust the dispersion angle due to temperature changes and environmental factors.

Accordingly, it is an object of the present invention to provide a wavelength demultiplexer having a simple configuration and capable of simultaneously dividing a plurality of carriers from wavelength division multiplexed light.
It is a further object of the present invention to provide a device capable of accurately demultiplexing wavelength division multiplexed light having a relatively large number of closely spaced carriers or wavelength components.

  In one embodiment of the present invention, an apparatus is provided that receives input light having each wavelength within a continuous wavelength range and generates a corresponding output light. Thereby, the output light can be spatially distinguished from the output light formed for the input light having another wavelength in the continuous wavelength region (for example, the output light travels in a different direction).

  More specifically, the device receives input light having each wavelength within a continuous wavelength range, and the device causes self-interference by multiple reflections of the input light, thereby forming output light. Thus, the output light can be spatially distinguished from the output light of the input light having another wavelength in the continuous wavelength region. The device is referred to as a virtual image phase array (VIPA).

  Further, according to one aspect of the present invention, there is provided an apparatus in which a VIPA is combined with a wavelength splitter such as a diffraction grating or a “demultiplexer”. More specifically, the VIPA receives input light and produces corresponding output light that propagates from the VIPA. The output light includes different wavelength components, such as a plurality of different carriers. The splitter splits the output light into a plurality of separated lights corresponding to a plurality of different wavelength components in the output light. Preferably, the duplexer has a dispersion direction substantially perpendicular to the dispersion direction of the VIPA. In this case, the light separated from the splitter is detected by the fibers arranged in a lattice pattern. This makes it possible to accurately split a wavelength division multiplexed light having a relatively large number of close carriers or wavelength components.

  Further, according to one embodiment of the present invention, an apparatus for splitting input light including a plurality of lights is provided. The plurality of lights have different wavelengths. The device includes a first duplexer and a second duplexer. The first splitter splits the input light into a plurality of output lights respectively corresponding to the plurality of lights in the input light. The first splitter disperses the plurality of output lights at a different output angle in a substantially linear dispersion direction for each output light. Further, each output light includes a plurality of wavelength components. The second splitter splits each output light into a plurality of separated lights corresponding to a plurality of wavelength components in the output light. The second splitter splits the plurality of separated lights in a substantially linear dispersion direction at different output angles for each of the separated lights. The dispersion direction of the second duplexer is not parallel, but preferably perpendicular, to the dispersion direction of the first duplexer. This makes it possible to accurately demultiplex a wavelength division multiplexed light having a relatively large number of close carriers or wavelength components.

  According to the present invention, wavelength division multiplexed light having three or more wavelength carriers can be separated at a time. Therefore, it is possible to reduce the size of the light receiver used in the optical multiplexing type optical communication.

  According to the present invention, different wavelength carriers are output at a larger dispersion angle than the diffraction grating. Accordingly, since the dispersion angle is large, the light receiver can accurately receive the dispersed light obtained by separating the wavelength division multiplexed light having a large number of carriers having relatively close wavelengths.

  According to the present invention, input light having each wavelength within a continuous wavelength region is received, and self-interference is caused in multiple reflection of the input light, thereby forming output light. Thus, the output light can be spatially distinguished from the output light formed for the input light having another wavelength in the continuous wavelength region. In addition, since multiple reflection is used, the phase of each light beam is constant, so that the characteristics are hardly affected by the polarization of the input light as in a diffraction grating. Also, unlike an arrayed waveguide grating, characteristics are hardly affected by the environment.

  Further, according to the present invention, a VIPA is combined with a wavelength splitter or "demultiplexer" such as a diffraction grating. The VIPA receives input light and generates corresponding output light propagating from the VIPA, and the demultiplexers each convert a plurality of separated lights corresponding to a plurality of different wavelength components in the output light. , And demultiplexes the output light. This makes it possible to accurately split a wavelength division multiplexed light having a relatively large number of close carriers or wavelength components.

  Further, according to the present invention, a first splitter and a second splitter are provided, and input light including a plurality of lights is split. The first splitter splits each of the input lights into a plurality of output lights corresponding to the plurality of lights in the input light, and substantially splits the plurality of output lights for each output light. Are dispersed at different output angles in a linear dispersion direction. Further, the second demultiplexer demultiplexes each output light into a plurality of separated lights corresponding to a plurality of wavelength components in the output light, and outputs the plurality of separated lights. Demultiplex at a different output angle for each separated light in a substantially linear dispersion direction. This makes it possible to accurately demultiplex a wavelength division multiplexed light having a relatively large number of close carriers or wavelength components.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same elements are denoted by the same reference numerals.
FIG. 1 is a configuration diagram of a virtual image phase array (VIPA) according to an embodiment of the present invention. Hereinafter, the terms "wavelength splitter", "virtual image phase array" or "VIPA" will be used interchangeably.

  As shown in FIG. 1, the VIPA 76 is preferably made of a thin glass plate. The input light 77 is focused on a line 78 by a lens 80, such as a semi-cylindrical lens, so that the input light 77 travels through the VIPA 76. Hereinafter, the line 78 is referred to as a “focal line 78”. The input light 77 propagates radially from the focal line 78 and is received inside the VIPA 76. Thereafter, the VIPA 76 outputs the light beam 82 of the collimated light. Here, the output angle of the light beam 78 changes as the wavelength of the input light 77 changes. For example, when the input light 77 has the wavelength λ1, the VIPA 76 outputs the light flux 82a at the wavelength λ1 in a specific direction. When the input light 77 has the wavelength λ2, the VIPA 76 outputs the light flux 82b at the wavelength λ2 in a different direction. If the input light 77 is a wavelength division multiplexed light obtained by combining the light having the wavelength λ1 and the light having the wavelength λ2, the VIPA 76 outputs the two separated light beams 82a and 82b simultaneously in different directions. Accordingly, the VIPA 76 generates light fluxes 82a and 82b that can be spatially distinguished from each other. Similarly, the VIPA 76 can simultaneously separate two or more different carrier lights from the wavelength division multiplexed light.

  FIG. 2 is a cross-sectional view taken along the line VII-VII of the VIPA 76 shown in FIG. 1 according to the embodiment of the present invention. As shown in FIG. 2, VIPA 76 includes a glass-like member 84 having reflective surfaces 86 and 88 on the surface. The reflecting surfaces 86 and 88 are parallel to each other and are separated by a distance t. The reflective surfaces 86 and 88 are generally reflective films deposited on the member 84. As will be described in more detail below, the reflective surface 88 has a reflectivity of about 100% except for the irradiation window 90. The reflecting surface 86 has a reflectance of about 95%. Accordingly, reflective surface 86 has a transmittance of approximately 5%, such that approximately 5% of the light incident on reflective surface 86 is transmitted and approximately 95% of the light is reflected.

  The reflectivity can be easily changed by special application of VIPA. However, in general, the reflection surface 86 needs to have a reflectance of less than 100% so that a part of incident light can be transmitted.

  The reflection surface 88 has an irradiation window 90. The irradiation window 90 transmits light and has as little reflection as possible or very low reflectance. Illumination window 90 receives input light 92 such that input light 92 is received and reflected between reflective surfaces 86 and 88.

  FIG. 2 shows a cross section along the line VII-VII in FIG. 1, so that the focal line 78 in FIG. 1 is seen as a "point" in FIG. Input light 92 then propagates radially from focal line 78. Further, as shown in FIG. 2, the focal line 78 is located on the reflection surface 86. It is not necessary that the focal line 78 be on the reflective surface 86, but a change in the arrangement of the focal line 78 will cause only a small change in the characteristics of the VIPA 76.

As shown in FIG. 2, the input light 92 enters the member 84 via the area A0 of the irradiation window 90. Here, the point P0 indicates a point around the area A0.
Due to the reflectivity of the reflective surface 86, about 5% or less of the input light 92 passes through the reflective surface 86 as transmitted light Out0 defined by ray R0, and about 95% or more of the input light 92 The light is reflected by the reflection surface 86 and enters the area A1 of the reflection surface 88. The point P1 indicates a point around the area A1. After being reflected at the area A1 on the reflection surface 88, the input light 92 proceeds to the reflection surface 86, and is partially transmitted through the reflection surface 86 as transmitted light Out1 defined by the ray R1. Thus, as shown in FIG. 2, the input light 92 is multiple-reflected between the reflecting surfaces 86 and 88. Here, each reflection of the reflection surface 86 becomes each transmitted light transmitted through the reflection surface 86. Thus, for example, each time the input light 92 is reflected by the areas A2, A3, and A4 on the reflective surface 88, the input light 92 is reflected by the reflective surface 86 to generate transmitted light Out2, Out3, and Out4, respectively. . Point P2 indicates a point around the area A2, point P3 indicates a point around the area A3, and point P4 indicates a point around the area A4. The transmitted light Out2 is defined by a ray R2, the transmitted light Out3 is defined by a ray R3, and the transmitted light Out3 is defined by a ray R3. In FIG. 2, only transmitted light Out1, Out2, Out3, and Out4 are shown, but actually, more transmitted light exists depending on the power of the input light 92 and the reflectivity of the reflecting surfaces 86 and 88. It is possible to do.

As will be described in more detail below, the transmitted light interferes with each other to produce a light flux as output light. The direction of the output light changes according to the wavelength of the input light 92.
FIG. 2 shows an example of the input light 92 having one wavelength. However, if the input light consists of multiple wavelengths (such as wavelength division multiplexed light consisting of multiple carriers of different wavelengths), the input light is similarly reflected. Note that the plurality of light beams are formed corresponding to the plurality of carriers, respectively. Each light beam is output from the VIPA at a different angle from the other light beams.

  FIG. 3 is a diagram illustrating interference between reflected lights generated by a VIPA according to an embodiment of the present invention. As shown in FIG. 3, light traveling from the focal line 78 is reflected by the reflecting surface 88 and then by the reflecting surface 86. As mentioned above, the reflective surface 88 has a reflectivity of about 100% and thus functions essentially like a mirror. As a result, the transmitted light Out1 can be analyzed optically, as if the transmitted light Out1 were emitted from the focal line I1, without the reflective surfaces 86 and 88 being present. Similarly, transmitted light Out2, Out3, and Out4 can be analyzed optically as if emitted from focal lines I2, I3, and I4, respectively. The focal lines I2, I3, and I4 are virtual images of the focal line I0.

  Therefore, as shown in FIG. 3, the focal line I1 is separated from the focal line I0 by a distance 2t. Here, t is equal to the distance between the reflecting surfaces 86 and 88. Similarly, each subsequent focal line is separated by a distance 2t from the immediately preceding focal line. Thus, the focal line I2 is separated from the focal line I1 by the distance 2t. Further, each subsequent multiple reflection between reflective surfaces 86 and 88 produces transmitted light having a lower intensity than the previous transmitted light. Therefore, the intensity of the transmitted light Out2 is lower than that of the transmitted light Out1.

  As shown in FIG. 3, the transmitted light from the focal line overlaps and interferes with each other. Further, the focal lines I1, I2, I3, and I4 are virtual images of the focal line I0, and thus the transmitted light Out1, Out2, Out3, and Out4 have the same optics at the positions of the focal lines I0, I1, I2, I3, and I4. It has a proper phase. Thus, this interference produces a beam that travels in a particular direction depending on the wavelength of the input light 92.

  The VIPA according to the above-described embodiment of the present invention has a constructive condition which is a feature of the design of the VIPA. Constructive conditions increase the interference of transmitted light such that a light beam is formed. The condition for constructing VIPA is expressed by the following equation (1).

2t × cos θ = mλ (1)
Where θ is the direction of propagation of the resulting light flux, measured from a line perpendicular to the reflective surfaces 86 and 88, λ is the wavelength of the input light, t is the distance between the reflective surfaces 86 and 88, and m is Indicates an integer.

Thus, if t is a constant and m is given a particular value, the direction of propagation of the luminous flux formed for the input light having wavelength λ is determined.
More specifically, the input light diverges radially from focal line 78 through a particular angle. Accordingly, input light having the same wavelength travels from focal line 78 in a number of different directions and is reflected between reflective surfaces 86 and 88. The constructive condition of VIPA enhances light traveling in a particular direction through the interference of transmitted light to form a light beam having a direction corresponding to the wavelength of the input light. Light traveling in different directions than the specific direction required by the constructive conditions is weakened by the interference of transmitted light.

  Further, when the input light includes light having a plurality of different wavelengths, the constructive condition forms a different luminous flux for each wavelength in the input light. Each light beam has a different wavelength. Accordingly, the VIPA can receive the wavelength division multiplexed light, travel in different directions, and generate a plurality of light beams corresponding to various wavelengths in the wavelength division multiplexed light.

  FIG. 4 is a diagram illustrating the formation of a light beam by the VIPA 76 according to an embodiment of the present invention, and is a diagram illustrating a cross section taken along line VII in FIG. More specifically, FIG. 3 shows a VIPA 76 capable of forming a plurality of light beams. Here, each light beam has a different propagation direction depending on the wavelength of the input light.

  As shown in FIG. 4, input light having a plurality of wavelengths is radially dispersed from focal line 78 such that the input light is reflected between reflective surfaces 86 and 88. Assume that the input light includes light having three different wavelengths. Thus, light having each wavelength is dispersed from the focal line 78 in many different directions. In order to form a light beam having a direction corresponding to the wavelength of the input light, the constructive conditions of the VIPA are such that light traveling in a particular direction at the same wavelength is enhanced by light traveling in a different direction. Thus, for example, light having a wavelength λ1 and propagating in the direction θ1 from the focal line 78 is enhanced by light traveling in different directions to form a light beam LF1 having a propagation direction θ1. Similarly, light having a wavelength λ2 and propagating in the direction θ2 from the focal line 78 is enhanced by light traveling in different directions to form a light beam LF2 having a propagation direction θ2. The light having the wavelength λ3 and propagating in the direction θ3 from the focal line 78 is enhanced by the light traveling in different directions to form a light beam LF3 having the propagation direction θ3.

  As mentioned above, equation (1) must be satisfied when increasing the interference between the transmitted light forming the light flux. Further, preferably, the thickness t of the member 84 is predetermined. Therefore, the angle range of incidence of the input light needs to be set so that the input light enters the VIPA 76 in the propagation direction θ that satisfies the expression (1). More specifically, it is possible to fix the propagation direction of the input light, fix the distance t between the reflection surfaces 86 and 88, and determine the wavelength of the input light in advance. Therefore, it is possible to determine a specific angle of the light beam generated for each wavelength in the input light, and it is possible to satisfy the constructive condition of the VIPA 76.

Further, since the input light radiates from the focal line 78 in many directions, the input light can surely propagate at an angle that satisfies the constructive condition.
FIG. 5 is a view showing a cross section of the VIPA shown in FIG. 1 taken along the line VII-VII. The VIPA according to one embodiment of the present invention is characterized by determining the angle of incidence or inclination of input light. Show.

  As shown in FIG. 5, the input light 92 is condensed by a cylindrical lens (not shown) and is focused on a focal line 78. As shown in FIG. 5, the input light 92 covers an area on the irradiation window 90 having a width equal to “a”. After the input light 92 is reflected once from the reflection surface 86, the input light 92 is incident on the reflection surface 88 and covers an area on the reflection surface 88 having a width equal to "b". Further, as shown in FIG. 5, the input light 92 travels along an optical axis 94, which is at an inclination angle θ1 with respect to the normal to the reflecting surface 86.

  When entering the VIPA, the input light 92 is prevented from leaking out of the member 84 through the irradiation window 90, and is not leaked out of the reflecting surface 88 after being reflected once by the reflecting surface 86. , The inclination angle θ1 should be set. That is, the tilt angle θ1 should be set such that the input light 92 cannot escape through the illumination window 90 while being “trapped” between the reflective surfaces 86 and 88. Therefore, the inclination angle θ1 should be determined according to the following equation (2) so that the input light 90 does not leak out of the member 84 through the irradiation window 90.

Inclination of optical axis θ1 ≧ (a + b) / 4t (2)
Accordingly, as shown in FIGS. 1 to 5, embodiments of the present invention include a VIPA that receives input light having each wavelength within a continuous wavelength range. VIPA causes self-interference by multiple reflections of input light, thereby forming output light. The output light is spatially distinguishable from the output light formed for the input light having another wavelength in the continuous wavelength range. For example, FIG. 2 shows input light 92 that is multiple reflected between reflective surfaces 86 and 88. This multiple reflection produces a plurality of transmitted lights Out0, Out1, Out2, Out3, and Out4 that interfere with each other to produce a light flux (such as the light fluxes LF1, LF2 or LF3 shown in FIG. 9).

  “Self interference” is a term that describes interference that occurs between multiple light or beams originating from the same source. Therefore, since the transmitted lights Out0, Out1, Out2, Out3, and Out4 are all generated from the same source (that is, the input light 92), the interference of the transmitted lights Out0, Out1, Out2, Out3, and Out4 is caused by the interference of the input light 92. It is called self-interference.

According to the embodiments of the present invention described above, the input light may be at any wavelength within a continuous wavelength range. As described above, the input light is not limited to the wavelength having the value selected from the discrete value range.
Further, according to the above-described embodiment of the present invention, the output light generated when the input light has different wavelengths within the continuous wavelength range and the input light having the specific wavelength within the continuous wavelength range are generated. The output light is spatially distinguishable. Therefore, for example, as shown in FIG. 1, when the input light 77 has a different wavelength within a continuous wavelength range, the traveling direction of the light flux 82 (that is, the “spatial characteristic”) is different. Although the output light can be spatially distinguished for two different wavelengths of the input light, it is not possible to generate spatially distinguishable output light for each wavelength in a continuous wavelength region of the input light. This operation can be compared with the conventional wavelength demultiplexer shown in FIGS. For example, in the filter of FIG. 19, all carriers having no wavelength λ2 in the wavelength division multiplexed light are output as light 28.

  FIG. 6 is a configuration diagram showing a VIPA used with a light receiver according to one embodiment of the present invention. As shown in the figure, the multilayer reflective films 96 and 98 are provided at both ends of a glass parallel plate 100 having a thickness t, for example, 100 μm. The parallel plate 100 preferably has a thickness in the range of 20 to 2000 μm. Desirably, the reflective films 96 and 98 are multilayer high reflectivity interference films.

  The reflectivity of the reflective film 98 is about 100%, and the reflectivity of the reflective film 96 is about 95%. However, the reflectivity of the reflective film 96 is not limited to 95%, and may be different as long as sufficient light is reflected from the reflective film 96 to cause multiple reflection between the reflective films 96 and 98. Good. Desirably, the reflectivity of the reflective film 96 is in the range of 80% to a few percent less than 100%. Further, the reflectivity of the reflective film 98 is not limited to 100%, but needs to be sufficiently high for multiple reflection between the reflective films 96 and 98.

  The irradiation window 102 receives the input light and is located on the parallel plate 100 and on the same surface as the reflection film 96. The irradiation window 102 can be formed by a film having a reflectance of about 0% on the surface of the parallel plate 100. As shown in FIG. 6, it is desirable that the boundary between the irradiation window 102 and the reflection film 96 be linear.

  The input light is output from, for example, an optical fiber (not shown) and received by the collimating lens 106. The collimating lens 106 converts the input light into the parallel beam 104, and the converted light is received by the cylindrical lens 108. The cylindrical lens 108 focuses the parallel beam 104 at a focal line 110 on the reflective film 98 or at a point in the parallel plate 100. Thus, the input light enters the parallel plate 100 through the irradiation window 102.

  The optical axis of the input light has a tilt angle with respect to the normal of the reflective film 96 so that the input light does not escape through the radiation window 102 after entering the parallel plate 100. For this purpose, the tilt angle is set according to the above equation (2).

  Once in parallel plate 100, the input light is multiple reflected between reflective films 96 and 98 (as shown in FIG. 2). Each time the input light is incident on the reflective film 96, about 95% of the input light is reflected toward the reflective film 98 and about 5% of the input light is transmitted through the reflective film 96 to form transmitted light (eg, , Like the transmitted light Out1 shown in FIG. 2). The multiple reflections between the reflective films 96 and 98 form a plurality of transmitted lights. The plurality of transmitted lights interfere with each other to form a light flux 112 having a propagation direction depending on the wavelength of the input light.

  The light beam 112 is then condensed by a lens 114, which focuses the light beam 112 at a focal point. The focal point moves along a linear line path 116 for different wavelengths of the input light. For example, as the wavelength of the input light increases, the focal point moves further along the linear line path 116. The plurality of light receivers 118 are arranged on the linear line path 116 to receive the focused light flux 112. Therefore, each light receiver 118 can be arranged to receive a light beam corresponding to a specific wavelength.

  By controlling the distance t between the reflective films or the reflective surfaces of the VIPA, the phase difference of the light reflected between the reflective films or the reflective surfaces can be shifted by a predetermined amount. Thereby, excellent environmental resistance is achieved. Further, in the above-described embodiments of the present invention, the change in the optical characteristics depending on the polarization is small.

FIG. 7 is a diagram showing a configuration of a VIPA used with a light receiver according to a further embodiment of the present invention.
The VIPA shown in FIG. 7 is similar to the VIPA shown in FIG. 6, except that the reflectances of the reflective films 96 and 98 are reversed. More specifically, in the VIPA shown in FIG. 7, the reflective film 98 has a reflectivity of about 95%, and the reflective film 96 has a reflectivity of about 100%. As shown in FIG. 7, the light flux 112 is formed through the interference of transmitted light traveling through the reflective film 98. As described above, the input light enters one side of the parallel plate 100, and the light beam 112 is formed on the opposite side of the parallel plate 100. In other respects, the VIPA shown in FIG. 7 operates similarly to the VIPA shown in FIG.

  FIG. 8 is a diagram showing a configuration of a VIPA according to still another embodiment of the present invention. As shown in FIG. 8, the plate 120 is made of, for example, glass, and has a reflective film thereon. The reflective film 122 has a reflectivity of about 95% or more, but less than 100%. The reflection film 124 has a reflectance of about 100%. The irradiation window 126 has a reflectance of about 0%.

  The input light 128 is focused on the focal line 129 by the cylindrical lens 130 via the irradiation window 126. The focal line 129 is on the surface of the plate 120 on which the reflective film 122 is provided. Thus, the focal line 129 is essentially a line focused on the reflective film 122 via the illumination window 126.

  When focused by cylindrical lens 130, the width of focal line 129 is referred to as the “beam waist” of input light 128. Thus, the embodiment of the present invention shown in FIG. 8 focuses the beam waist of input light 128 on the far surface of plate 120 (ie, the surface having reflective film 122 thereon). By focusing the beam waist onto the far surface of the plate 120, this embodiment of the invention provides (i) a plate that is covered by the input light 128 as the input light 128 passes through the illumination window 126. The area of illumination window 126 on the surface of surface 120 (eg, area “a” shown in FIG. 5) and (ii) the reflection covered by input light 128 when input light 128 was first reflected by reflective film 124 The potential for overlap with regions on film 124 (eg, region "b" shown in FIG. 5) can be reduced. It is desirable to reduce such duplication to ensure proper operation of the VIPA.

  8, the optical axis 132 of the input light 128 has a small inclination angle θ. After the initial reflection of the reflective film 122, 5% of the light passes through the reflective film 122 and spreads after the beam waist, and 95% of the light is reflected toward the reflective film 124. After first being reflected by the reflective film 124, the light strikes the reflective film 122 again, but is shifted by d. Thereafter, 5% of the light passes through the reflective film 122. Similarly, as shown in FIG. 8, light is split into many paths at a constant interval d. The beam shape of each pass causes light to spread from the virtual image 134 of the beam waist 129. The virtual images 134 are arranged at a constant interval 2t along a straight line that is a normal to the plate 120. Here, t is the thickness of the plate 120. The position of the beam waist in the virtual image 134 is self-aligned and does not need to be adjusted. Thereafter, the light emanating from the virtual image 134 interferes with one another to form collimated light 136 that propagates in a direction that varies according to the wavelength of the input light 128.

  The interval between light paths is d = 2tSinθ, and the difference in path length between adjacent beams is 2tCosθ. The angular variance is proportional to the ratio of these two numbers, cotθ. As a result, embodiments of the present invention produce very large angular dispersion between the luminous fluxes for different carriers, as compared to conventional wavelength demultiplexers.

  As described above, embodiments of the present invention are referred to as "virtual image phase arrays." As previously shown in FIG. 8, the term “virtual image phase array” originates from the formation of an array of virtual images 134.

FIG. 9 is a diagram showing a configuration of a waveguide VIPA according to one embodiment of the present invention.
As shown in FIG. 9, light 138 is output from an optical fiber (not shown) and received by a waveguide 140 provided on a substrate 142. The waveguide 140 is, for example, lithium niobate. The light 138 includes an optical signal obtained by modulating a plurality of carriers having different wavelengths.

The light 138 generally has a certain dispersion width when output from the optical fiber. Thus, collimating lens 142 converts light 138 to parallel light.
The parallel light is then collected by a cylindrical lens 144 and focused on a focal line 146. The light then radiates from the focal line 146 through the illumination window 150 to the VIPA 148.

  The VIPA 148 includes reflective films 152 and 154 on a parallel plate 156. The reflective film 154 is on one side of the parallel plate 156, and the reflective film 152 and the irradiation window 150 are on the other side of the parallel plate 156. The reflective film 152 has a reflectance of about 100%, and the reflective film 154 has a reflectance lower than 100%. The light beam 158 of the light reflected by the parallel plate 156 is output to the side of the parallel plate 156 opposite to the irradiation window 150.

  When the light 138 includes a plurality of wavelengths, a plurality of light beams 158 traveling in different directions depending on the wavelength of the input light 138 are formed. The light beam 158 formed by the VIPA 148 is focused to different points by the lens 160 depending on the propagation direction of the light beam 158. Therefore, as shown in FIG. 9, the light beams 158a, 158b, and 158c having the wavelengths λ1, λ2, and λ3 are formed at different light condensing points.

  The plurality of light receiving waveguides 162 are provided at the focal point. Each light receiving waveguide 162 guides an optical signal and a corresponding carrier having one wavelength. Therefore, a plurality of light beams can be received and transmitted simultaneously via various channels. Each light receiving waveguide 162 has a corresponding light receiver (not shown) provided at a subsequent stage. The light receiver is generally a photodiode. Thus, the light guided by each light receiving waveguide 162 is processed after being detected by the corresponding light receiver.

FIGS. 10, 11, 12 and 13 show a method for manufacturing a VIPA according to one embodiment of the present invention.
As shown in FIG. 10, the parallel plate 164 is desirably made of glass and has good parallelism. The reflective films 166 and 168 are formed on both sides of the parallel plate 164 by vacuum deposition, ion sputtering or other similar methods. One of the reflective films 166 and 168 has a reflectivity of approximately 100%, and the other desirably has a reflectivity of 80% or more and less than 100%.

  As shown in FIG. 11, one of the reflective films 166 and 168 has been partially shaved to form the irradiation window 170. In FIG. 11, the reflection film 166 is shaved to form the irradiation window 170 on the same surface of the reflection film 166 and the parallel plate 164. However, it is alternatively possible for the reflective film 168 to be partially ground to form the illumination window 170 on the same surface of the parallel plate 164 as the reflective film 168. The illumination window may be on either side of the parallel plate 164, as shown by various embodiments of the present invention.

  The shaving of the reflective film can be performed by an etching process. However, mechanical cutting processes can also be used and are less expensive. However, if the reflective film is mechanically scraped, the parallel plates 164 must be carefully treated to minimize damage to the parallel plates 164. For example, if a portion of the parallel plate 164 forming the illumination window is severely damaged, the parallel plate 164 creates extra loss caused by scattering of the received input light.

  Instead of the initial formation of the reflective film and subsequent cutting, the irradiation window is preliminarily masked on a part of the parallel plate 164 corresponding to the irradiation window to prevent this part from being covered with the reflective film. , Can be generated.

  As shown in FIG. 12, a transparent adhesive 172 is used on the reflective film 166 and a part of the parallel plate 164 from which the reflective film 166 is to be removed. Since the transparent adhesive 172 is used for a part of the parallel flat plate 164 forming the irradiation window, the transparent adhesive 172 should be made so as not to cause optical defects as much as possible.

  As shown in FIG. 13, the transparent protective plate 174 is used on the transparent adhesive 172 to protect the reflective film 166 and the parallel flat plate 164. Since the transparent adhesive 172 is used to fill the depressed portion obtained by removing the reflective film 166, the transparent protective plate 174 can be provided in parallel with the outermost surface of the parallel flat plate 164.

Similarly, to protect the reflective film 168, an adhesive (not shown) should be used on the outermost surface of the reflective film 168 to provide a protective plate (not shown).
If the reflective film 168 has a reflectivity of about 100% and there is no illumination window on the same surface of the parallel plate 164, the adhesive and the guard plate need not necessarily be transparent.

Further, the antireflection film 176 is used for the transparent protection plate 174. For example, the transparent protective plate 174 and the irradiation window 170 are covered with an antireflection film 176.
In the above-described embodiments of the present invention, it is assumed that the focal line is on the surface opposite to the surface of the parallel plate where the input light enters. However, the focal line may be in a parallel plate, on the illumination window, or in front of the illumination window.

  In the embodiment of the present invention described above, the two reflective films reflect light between the films, with one reflective film having a reflectivity of about 100%. However, a similar effect can be obtained with two reflective films each having a reflectance of less than 100%. For example, both reflective films may have a reflectivity of 95%. In this case, each reflective film has light that transmits through and causes interference. As a result, a light beam traveling in a direction depending on the wavelength is formed on both sides of the parallel plate on which the reflection film is formed. Thus, the various reflections of the various embodiments of the present invention can be easily varied according to the required properties of the VIPA.

  In the embodiment of the present invention described above, the VIPA is described as being formed by a parallel plate or two reflecting surfaces parallel to each other. However, the plates or reflecting surfaces need not necessarily be parallel.

According to the above-described embodiment of the present invention, light including a plurality of wavelengths can be split at the same time. Therefore, the light receiver used for the wavelength division multiplexing communication can be reduced in size.
According to the embodiment of the present invention described above, the VIPA can simultaneously split the wavelength division multiplexed light for each wavelength of light. Further, the angle of dispersion can be adjusted by the thickness t of the parallel plate forming the VIPA. As a result, the angle of dispersion can be made sufficiently wide so that the light receiver can easily receive each divided signal. For example, in a conventional diffraction grating, a fine uneven surface is required to obtain a large diffraction angle. However, it is difficult to tailor a fine and accurate uneven surface, and thus the size of the diffraction angle is limited. On the other hand, in the VIPA according to the above-described embodiment of the present invention, in order to obtain a relatively large angle of dispersion, it is only necessary to change the thickness of the parallel plate.

  Further, the VIPA according to the above-described embodiment of the present invention generates a larger dispersion angle than the conventional diffraction grating. Therefore, the photodetector using the VIPA according to the above-described embodiment of the present invention can accurately receive an optical signal without failure even in wavelength multiplexing communication that realizes advanced multiplexing processing. Moreover, such a receiver has a relatively simple structure and can be manufactured relatively inexpensively.

  According to the embodiments of the present invention described above, VIPAs use reflection to maintain a constant phase difference between interfering lights. As a result, the properties of the VIPA are stable, thereby reducing the change in optical properties caused by polarization. On the other hand, the optical characteristics of the conventional diffraction grating have changed unfavorably depending on the polarization of the input light.

  Furthermore, compared to arrayed waveguide gratings, the VIPAs according to the above-described embodiments of the present invention have a relatively simple structure and achieve stable optical characteristics and resistance to changes in environmental conditions.

  The above-described embodiments of the present invention are described as providing light beams that are "spatically distinguishable" from each other. "Spatially identifiable" means that the luminous flux is identifiable at intervals, for example, when various luminous fluxes are collimated and travel in different directions or are focused at different locations, the luminous flux is spatially distinguishable. It can be determined. However, the invention is not limited to such an example, and there are many other ways in which the light beams can be spatially distinguished from one another.

  VIPA has a free spectral region corresponding to the thickness t between the reflective surfaces of the VIPA (like the thickness t between the reflective surfaces 86 and 88 in FIG. 2). When VIPA is used as a wavelength demultiplexer, the free spectral region limits the wavelength band of VIPA. Generally, the wavelength band is substantially equal to the free spectral region. For example, when the thickness t is 50 μm, the wavelength band of VIPA is 16 nm, and the output angle for each successive 16 nm wavelength band is repeated.

  Therefore, the input light to the VIPA falls within a relatively wide wavelength range. This wavelength region is divided into a plurality of wavelength bands determined by the free spectral band of VIPA. The output angle from the VIPA is repeated for each wavelength band.

  It is often desirable to provide VIPA with a wide wavelength band. For example, recent technological advances have greatly increased the bandwidth of optical amplifiers. In order to efficiently split the light amplified by the optical amplifier, it is desirable to give the VIPA a wide wavelength band or bandwidth. For this, the thickness t between the reflective surfaces of the VIPA must be smaller. However, VIPA with a thickness t smaller than 50 μm cannot be easily produced.

  To solve this problem of limiting the wavelength band of VIPA, VIPA can be used in combination with a wavelength splitter (also referred to as a duplexer) to provide a device with a wide wavelength band.

More specifically, FIGS. 14 and 15 show an apparatus in which a duplexer and a VIPA are combined according to an embodiment of the present invention. FIG. 14 is a plan view of the apparatus, and FIG. 15 is a side view of the apparatus.
As shown in FIGS. 14 and 15, input light, such as wavelength division multiplexed light, travels from fiber 200 to collimating lens 210. The collimating lens 210 collimates the input light and supplies the collimated light to the semi-cylindrical lens 220. The semi-cylindrical lens 220 focuses light onto the VIPA 230.

  VIPA produces output light (such as a light beam) that is supplied to a demultiplexer such as diffraction grating 240. The diffraction grating 240 splits the light into a plurality of separated lights or light beams, and the plurality of separated lights or light beams are focused on the focal plane 260 by the focusing lens 250.

  In general, VIPAs such as VIPA 230 have relatively high resolution in a narrow wavelength range. For example, FIG. 16 is a graph showing wavelength versus output angle of VIPA. As shown in FIG. 16, a VIPA has a plurality of repeating wavelength bands 280 determined by the free spectral region of the VIPA. In general, the band of each wavelength band 280 is substantially equal to the free spectral region.

  As shown in FIG. 16, wavelengths λ1, λ2, λ3, λ4, and λ5 are each dispersed from VIPA at the same output angle θ. Therefore, the VIPA disperses the output light at an output angle θ having wavelength components corresponding to the wavelengths λ1, λ2, λ3, λ4, and λ5.

  On the other hand, FIG. 17 is a graph showing the wavelength versus the output angle of the diffraction grating. As shown in FIG. 17, the diffraction grating has a wide wavelength band 290 including wavelengths λ1, λ2, λ3, λ4, and λ5. The diffraction grating disperses the wavelengths λ1, λ2, λ3, λ4 and λ5 at output angles θ1, θ2, θ3, θ4 and θ5, respectively.

  From FIGS. 16 and 17, VIPA allows relatively close wavelengths within a wavelength band (such as wavelength band 280) to be output at greatly different output angles. Therefore, VIPA has a relatively high resolution even in a narrow wavelength band. On the other hand, diffraction gratings allow wavelengths to be split over a wide wavelength band, but the output angles are relatively close to each other. Therefore, the diffraction grating has a relatively low resolution even in a wide wavelength band.

  14 and 15 can be easily understood by referring to the resolution of the VIPA 230 and the diffraction grating 240. More specifically, referring again to FIGS. 14 and 15, the input light is first split by a relatively high-resolution VIPA 230 and then further split by a relatively low-resolution diffraction grating 240.

  FIG. 18 shows an operation example of the VIPA-diffraction apparatus according to one embodiment of the present invention. As shown in FIG. 18, the VIPA 230 receives input light 295 having wavelengths λ1, λ2, λ3, λ4, λ5, λ6, λ7, λ8, λ9, λ10, λ11 and λ12. As a result, the VIPA 230 generates a plurality of light beams or output lights 300, 310, 320, 330, and 340 that propagate from the VIPA 230. Output light 300 includes wavelengths λ1, λ6, and λ11. Output light 310 includes wavelengths λ2, λ7, and λ12. Output light 320 includes wavelengths λ3 and λ8. Output light 330 includes wavelengths λ4 and λ9. Output light 340 includes wavelengths λ5 and λ10.

  The diffraction grating 240 receives the output lights 300, 31, 320, 330, and 340, and separates each of the output lights into separated light corresponding to a wavelength in the output light. For example, diffraction grating 240 splits output light 300 into three separate lights having wavelengths λ1, λ6, and λ11.

  When the VIPA 230 disperses the output light in the dispersion direction, which is not parallel to the dispersion direction in which the diffraction grating 240 disperses the separated light, the combination of the VIPA 230 and the diffraction grating 240 allows a relatively large number of closely spaced wavelengths. The wavelength division multiplexed light having the component can be accurately demultiplexed.

  For example, FIG. 18 shows a grid 350 having points 1 to 12 in a grid pattern. Points 1 to 12 represent the ends of the individual fibers. If the dispersion direction of the VIPA 240 is substantially perpendicular to the dispersion direction of the diffraction grating 240, the separated light generated by the diffraction grating 240 can be received by the fibers arranged in a grating pattern. is there. With this configuration, wavelength division multiplexed light having a relatively large number of spatially close wavelength components can be accurately split.

  The dispersion angle of VIPA 240 is not limited to being substantially perpendicular to the dispersion angle of diffraction grating 240. For example, the directions of dispersion can simply be "not parallel" to each other. Furthermore, the present invention is not limited by the relationship of the dispersion directions. Therefore, depending on the application, it may be appropriate that the dispersion directions are parallel.

  It should be understood that both the VIPA and the diffraction grating output light at an output angle in a certain dispersion direction. Accordingly, VIPA 230 generates a plurality of output lights, each of which is dispersed from the VIPA at a different output angle. However, the output light is dispersed in the same dispersion direction. In FIG. 18, it is desirable that both the dispersion directions of the VIPA 230 and the diffraction grating 240 are substantially linear. For example, in FIG. 18, the dispersion direction of the VIPA 230 may be perpendicular to the figure, and the dispersion direction of the diffraction grating 240 may be horizontal to the figure. In this case, the dispersion directions are perpendicular to each other.

  With the device shown in FIG. 18, it is possible to split the input light within a wide wavelength range very accurately and with high resolution. For example, if the VIPA 230 splits 20 wavelengths at 0.8 nm intervals in the 16 nm wavelength band and the diffraction grating 240 splits 5 wavelengths in each VIPA wavelength band, 100 wavelengths at 0.08 nm intervals will be used. , 80 nm.

  In the embodiment of the present invention described above, the diffraction grating 240 is used as a duplexer. However, the invention is not limited to the use of a diffraction grating. Alternatively, other suitable duplexers can be used. For example, a multilayer interference film may be used.

  According to the embodiment of the invention described above, the device comprises a VIPA and a duplexer, for example a diffraction grating. VIPA receives input light having wavelengths in a continuous wavelength range. As a result, the VIPA produces a corresponding output light that propagates from the VIPA. Output light is dispersed from the VIPA in a substantially linear dispersion direction at different output angles for each wavelength. Further, the dispersed output light includes a plurality of different wavelength components. The demultiplexer splits the output light into a plurality of separated lights, each corresponding to a plurality of different wavelength components in the output light. The split lights are split by the splitter in a substantially linear spreading direction at different output angles for each split light. It is desirable that the dispersion direction of the VIPA is not parallel to the dispersion direction of the duplexer but is perpendicular. The focal plane may include a lens that focuses the plurality of separated lights. Here, each separated light is focused to a different point on the focal plane than the other separated light.

  Generally, input light is wavelength division multiplexed light that includes two or more lights of different wavelengths. The VIPA then forms each output light for each input light. Each output light is spatially distinguishable from the other output lights, and each includes a plurality of different wavelength components. In this case, the demultiplexers each split the output light into separated lights corresponding to a plurality of different wavelength components in the output light. Then, it is possible to provide a lens to focus the light separated from the duplexer on the focal plane. If the direction of dispersion of the VIPA is substantially perpendicular to the direction of dispersion of the duplexer, each separated light is combined with the other separated light to form a grating pattern on the focal plane. It is possible to focus to different points on the focal plane.

  For example, as shown in FIG. 18, according to an embodiment of the present invention, an apparatus splits input light including a plurality of lights, each having a different wavelength. The apparatus includes first and second duplexers. For example, in FIG. 18, the VIPA 230 operates as a first splitter, and the diffraction grating 240 operates as a second splitter. The first splitter splits the input light into a plurality of output lights corresponding to a plurality of lights in each input light. The first demultiplexer disperses the plurality of output lights in a substantially linear dispersion direction at different output angles with respect to the respective output lights. Further, each output light includes a plurality of wavelength components. The second demultiplexer splits the output light into a plurality of separated lights corresponding to a plurality of wavelength components in each output light. The second splitter disperses the plurality of separated lights in a substantially linear dispersion direction at different output angles for each separated light. It is desirable that the dispersion direction of the second duplexer is not parallel to the dispersion direction of the first duplexer but is perpendicular. The first and second duplexers are not limited to VIPA and diffraction grating. Alternatively, a suitable splitter or wavelength splitter can be used.

  In general, a VIPA is an angular dispersion component having a passage area for receiving light from itself and outputting the light from itself. Via the passband, the VIPA receives input light with each wavelength in a continuous wavelength range. VIPA causes self-interference to form output light by multiple reflection of input light. The output light proceeds from the VIPA and is spatially distinguishable from the output light generated for input light having another wavelength in a continuous wavelength range.

  Here, various lenses are disclosed. For example, FIG. 14 discloses the use of a collimating lens 210, a semi-cylindrical lens 220 and a focusing lens 250. However, the invention is not limited to the use of any type of lens. Alternatively, different types of lenses or devices can be used to achieve the appropriate effect.

  Here, the word “plurality” means “more than one”. Thus, a plurality of lights refers to "more than one" light. For example, the two lights are a plurality of lights.

FIG. 2 is a diagram showing a configuration of a virtual image phase array (VIPA) according to an embodiment of the present invention. FIG. 7 is a diagram illustrating a cross section taken along line VII-VII of the VIPA illustrated in FIG. 1 according to the embodiment of the present invention. FIG. 4 is a diagram illustrating interference between reflections generated by a VIPA according to an embodiment of the present invention. FIG. 7 is a cross-sectional view of the VIPA shown in FIG. 1 taken along the line VII-VII in order to illustrate formation of a light beam according to one embodiment of the present invention. FIG. 7 is a diagram illustrating a cross section taken along a line VII-VII of the VIPA illustrated in FIG. 1 and illustrating a characteristic of a VIPA that determines an inclination angle of input light according to the embodiment of the present invention. FIG. 4 is a diagram illustrating a VIPA when used with a light receiver according to one embodiment of the present invention. FIG. 4 is a diagram showing a configuration of a VIPA when used with a light receiver according to a further embodiment of the present invention. FIG. 11 is a diagram illustrating a configuration of a VIPA according to another embodiment of the present invention. FIG. 3 is a diagram illustrating a waveguide VIPA according to one embodiment of the present invention. FIG. 4 is a diagram (part 1) illustrating a method of creating a VIPA according to an embodiment of the present invention. FIG. 6 is a diagram (part 2) illustrating a VIPA creation method according to an embodiment of the present invention. FIG. 11 is a diagram (part 3) illustrating a method of creating a VIPA according to one embodiment of the present invention. FIG. 11 is a diagram (part 4) illustrating a method of creating a VIPA according to an embodiment of the present invention. FIG. 3 is a plan view of an apparatus in which a duplexer such as a diffraction grating and VIPA are combined according to an embodiment of the present invention. FIG. 4 is a side view of an apparatus in which a duplexer such as a diffraction grating and VIPA are combined according to an embodiment of the present invention. 4 is a graph showing wavelength versus output angle of VIPA according to one embodiment of the present invention. 5 is a graph showing wavelength versus output angle of a diffraction grating. It is a figure which shows the operation example of a VIPA-diffraction grating concerning one Example of this invention. It is a figure showing the conventional filter using a multilayer interference film. FIG. 2 is a diagram showing a conventional Fabry-Perot interferometer. FIG. 9 is a diagram illustrating a conventional Michelson interferometer. FIG. 9 is a diagram illustrating a conventional diffraction grating. FIG. 2 is a diagram showing a conventional arrayed waveguide grating for demultiplexing wavelength division multiplexed light.

Explanation of reference numerals

76 Virtual Image Phase Array (VIPA)
77 input light 78 lines (focal line)
80 lens 82 light beam 84 member 86 reflecting surface 88 reflecting surface 90 irradiation window 92 input light 94 optical axis 96 reflecting surface 98 reflecting surface 100 parallel plate 104 parallel beam 106 collimating lens 108 cylindrical lens 110 focal line 112 light beam 114 lens 116 Linear line path 118 Light receiver 120 Plate 122 Reflecting film 124 Reflecting film 126 Irradiation window 128 Input light 129 Beam waist 130 Cylindrical lens 132 Optical axis 134 Virtual image 136 Light 137 Substrate 138 Light 140 Waveguide 142 Collimating lens 144 Cylindrical Lens 146 Focal line 148 VIPA
150 Irradiation window 152 Reflective film 154 Reflective film 156 Parallel plate 158 Light beam 160 Lens 162 Light receiving waveguide 164 Parallel plate 166 Reflective film 168 Reflective film 170 Irradiation window 172 Transparent adhesive 174 Protective plate (protective plate)
176 Anti-reflection film 200 Fiber 210 Collimating lens 220 Semi-cylindrical lens 230 VIPA
240 diffraction grating 250 focusing lens 260 focal plane 280 wavelength band 290 wide wavelength band 295 input light 300, 310, 320, 330, 340 output light 350 grating a, b width OUT0, OUT1, OUT2, OUT3, OUT4 transmitted light R1, R2 , R3, R4 Rays P1, P2, P3, P4 Point A1, A2, A3, A4 Area I0, I2, I3, I4, I5, I6 Focus line LF1, LF2, LF3 Light beam Q1, Q2, Q3 Propagation direction θ1 Inclination angle t Thickness d Amount λ1 to λ12 Wavelength θ1, θ2, θ3, θ4, θ5 Output angle

Claims (1)

A virtual image phase array (VIPA) element in which the focused input light is propagated between the first and second reflecting surfaces to form a virtual image array and output, so that the emission angle of the interference light repeats at a predetermined wavelength. When,
An apparatus comprising: a splitter that splits output light from the VIPA element into a plurality of light beams having different wavelengths in a direction different from the angle-dispersed direction.

Images