JP2017003670A - Hybrid Integrated Optical Transmitter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical transmitter in which optical modulators using a compound semiconductor are integrated, with which it is possible to form a passive optical element by a simple method and realize further downsizing and still higher performance.SOLUTION: The present invention is a hybrid integrated type optical transmitter characterized in that a first input/output waveguide, an optical amplifier, a reflector, a 1×2 coupler, first and second optical modulators, and first and second output waveguides are monolithically integrated on a first substrate, and a second input/output waveguide, a wavelength filter circuit, first and second input waveguides, a polarization rotator, a polarized wave combiner, and a combined wave optical output waveguide are monolithically integrated on a second substrate, the optical amplifier, the reflector and the wavelength filter circuit being designed so as to constitute a single wavelength oscillation laser unit, the first substrate being composed of a compound semiconductor material, the second substrate being composed of a material different from the first substrate.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a small hybrid integrated optical transmitter.

  Optical transmitters are strongly required to have a small module size as well as their transmission performance. An optical transmitter is generally composed of a light source element typified by a semiconductor laser and a modulator for putting information on light output from a light source typified by an electroabsorption optical modulator or a Mach-Zehnder interferometric modulator. .

  With regard to modulators, elements that use a ferroelectric material typified by lithium niobate as a material have been mainly used in the past, particularly in a long-distance and large-capacity optical line such as a core network. However, in recent years, optical transmitters are increasingly required to be smaller and consume less power. Recently, modulators based on compound semiconductors that can reduce power consumption and size compared to conventional ferroelectric modulators. Is attracting attention.

  As representatives of modulators that take advantage of the compactness of compound semiconductors, etc., a duplexer that splits input light into two branches, two modulators that modulate individual lights for each of the two split lights, and 2 There is a polarization multiplexing modulator in which a multiplexer for multiplexing modulated light modulated by two modulators and a monolithically integrated on the same substrate. In a polarization multiplexing modulator, two orthogonal lights are rotated by rotating the polarization of one of the two modulated lights of the same polarization with a modulator and then combining them with a multiplexer. A polarization multiplexed signal in which a signal independent of polarization is carried can be generated. With such a monolithic modulator formed of a compound semiconductor, there is an advantage that a polarization multiplexing transmitter can be configured in a small module.

  Furthermore, a major advantage of configuring a modulator with a compound semiconductor is that it is more suitable in addition to an optical amplifier that amplifies light in the modulator by growing a semiconductor material having an optically active composition on the same substrate, and an optical amplifier. By integrating a simple wavelength selection mechanism (filter), it is possible to achieve high functionality that realizes a laser element on the same substrate.

Nobuhiro Kikuchi et al., “80-Gbitls InP DQPSK modulator with an n-p-i-n structure”, in Proc. Of ECOC 2007, 10.3.1, 2007. Yuta Ueda et al., “Very-low-voltage operation of Mach-Zehnder interferometer-type electroabsorption modulator using asymmetric couplers”, Opt. Express, vol. 22, issue 12, pp. 14610-14616, 2014.

  As described above, optical modulators using compound semiconductors have many advantages. On the other hand, as a common problem for optical devices using compound semiconductors, compound semiconductors are generally used in passive optical circuits such as glass and silicon. There is a point that it is difficult to process. For example, in the above-described polarization multiplexing transmitter, ideally, if the polarization rotator and the polarization multiplexer can be monolithically integrated on the same substrate as the modulator, further miniaturization of the transmitter module can be expected. However, it is difficult to manufacture these polarization control elements on a compound semiconductor substrate due to the difficulty in processing compound semiconductors. Laser integrated modulators also require a variable wavelength selection filter for single-wavelength oscillation and oscillation wavelength control, and this also generally requires a high process technology for fabrication on a compound semiconductor substrate. .

  The present invention relates to an optical transmitter in which an optical modulator using a compound semiconductor substrate is integrated in order to further reduce the size and performance of a modulator made of a compound semiconductor. A method for easily realizing an optical element is provided.

  In order to achieve the above object, a hybrid integrated optical transmitter according to claim 1 is a hybrid integrated optical transmitter including an optical amplification modulator and a wavelength / polarization control circuit, wherein the optical amplification is performed. The modulator reflects the first input / output waveguide, an optical amplifier that amplifies the light input from the first input / output waveguide, and a part of the amplified light output from the optical amplifier to reflect the light A reflector for returning to the first input waveguide side, a 1 × 2 coupler connected to the optical amplifier via the reflector, and for branching the amplified light input from the optical amplifier through the reflector into two branches The first optical modulator that generates the first modulated light by modulating one branched light output from the 1 × 2 coupler, and the other branched light output from the 1 × 2 coupler. A second optical modulator for generating a second modulated light by modulating; A first output waveguide for outputting the first modulated light generated by the first optical modulator, and the second modulated light generated by the second optical modulator; The second output waveguide is monolithically integrated on the first substrate, and the wavelength / polarization control circuit is incident from the second input / output waveguide and the second input / output waveguide. A wavelength filter circuit that selectively reflects light having a specific wavelength with respect to the wavelength of the reflected light and outputs the reflected light to the second input / output waveguide; and outputs from the first output waveguide A first input waveguide for inputting the first modulated light, a second input waveguide for inputting the second modulated light output from the second output waveguide, and Polarization rotation for rotating the polarization of the first modulated light input from the first input waveguide to generate polarization rotation light A polarization combiner that combines the second modulated light and the polarization rotation light, and a combined light output waveguide that outputs the combined light combined by the polarization combiner. Monolithically integrated on the second substrate, the optical amplifying modulator and the wavelength / polarization control circuit are integrated in the same optical module, of the naturally occurring light emitted from the optical amplifier The optical amplifier, the reflector, and the wavelength filter circuit are designed so as to constitute a single wavelength oscillation laser unit that selectively oscillates only light of a specific wavelength reflecting the characteristics of the wavelength filter circuit, The first substrate is made of a compound semiconductor material having an optical gain, and the second substrate is made of a material different from that of the first substrate.

  The hybrid integrated optical transmitter according to claim 2 is the hybrid integrated optical transmitter according to claim 1, wherein the second substrate is made of silicon or a glass-based material. And

  A hybrid integrated optical transmitter according to claim 3 is the hybrid integrated optical transmitter according to claim 1 or 2, wherein the first input / output waveguide, the first output waveguide, and the The second output waveguides are respectively disposed on the same cut surface of the first substrate, and the second input / output waveguide, the first input waveguide, and the second input waveguide are: Each of the second substrates is disposed on the same cut surface of the second substrate.

A hybrid integrated optical transmitter according to claim 4 is the hybrid integrated optical transmitter according to any one of claims 1 to 3, wherein the first input / output waveguide and the second input / output are provided. A first lens for optically coupling a waveguide; a second lens for optically coupling the first output waveguide and the first input waveguide; the second output waveguide; And a third lens for optically coupling the second input waveguide.
Each end face of the first input / output waveguide, the first output waveguide and the second output waveguide, and / or the second input / output waveguide, the first input waveguide, and the It further includes a spot size converter provided on each end face of the second input waveguide, which changes a mode distribution guided through the waveguide.

  The hybrid integrated optical transmitter according to claim 6 is the hybrid integrated optical modulator according to any one of claims 1 to 5, wherein the wavelength filter circuit reflects a reflected wavelength with respect to an input electric signal. It has the mechanism which changes.

  The hybrid integrated optical transmitter according to claim 7 is the hybrid integrated optical modulator according to any one of claims 1 to 6, wherein the wavelength / polarization control circuit includes the first modulated signal. It further includes a monitor photodetector for monitoring light intensity of the light and the second modulated light.

  The hybrid integrated optical transmitter according to claim 8 is the hybrid integrated optical modulator according to any one of claims 1 to 7, wherein the wavelength / polarization control circuit includes the wavelength filter circuit and the wavelength filter circuit. A part of the oscillation light connected to the first input waveguide and outputted from the single wavelength oscillation laser unit is inputted through the wavelength filter circuit and the first modulated light is inputted, and the inputted oscillation Connected to the first optical hybrid circuit for combining a part of light and the first modulated light, the wavelength filter circuit and the second input waveguide, and output from the single wavelength oscillation laser unit A part of the oscillation light input through the wavelength filter circuit, the second modulated light is input, and the second part of the input oscillation light and the second modulated light are combined. A hybrid circuit, Characterized in that it comprises the al.

  ADVANTAGE OF THE INVENTION According to this invention, the further size reduction and performance enhancement of the optical transmitter with which the modulator by a compound semiconductor was integrated can be implement | achieved by a simple method, and it can contribute to the further spread of optical communication.

1 is a schematic diagram of an optical transmitter according to the present invention. 1 is a schematic diagram of an optical amplifier integrated modulator constituting an optical transmitter according to Embodiment 1 of the present invention. FIG. 1 is a schematic diagram of a wavelength / polarization control circuit constituting an optical transmitter according to Embodiment 1 of the present invention. FIG. FIG. 3 is a diagram illustrating a specific configuration example of a wavelength filter circuit according to the first embodiment. It is a figure which illustrates the structure of the optical transmitter which concerns on Example 1 of this invention. It is a figure which illustrates the structure of the optical transmitter which concerns on Example 2 of this invention. It is a figure which illustrates the structure of the wavelength filter circuit in the optical transmitter which concerns on Example 3 of this invention. It is a figure which illustrates the structure of the optical transmitter which concerns on Example 4 of this invention. It is a figure which illustrates the structure of the optical transmitter which concerns on Example 5 of this invention.

  FIG. 1 shows a schematic diagram of an optical transmitter according to the present invention. FIG. 1 shows an optical amplifier integrated modulator 10 in which active elements such as an optical amplifier and an optical modulator are monolithically integrated, and a wavelength filter circuit that selectively reflects light with respect to the wavelength of incident light. A wavelength / polarization control circuit 20 monolithically integrated with passive elements such as a polarization rotator for rotating the polarization of the polarized light and a polarization multiplexer for combining light of different polarizations incident from different paths; The optical transmitter shown in FIG. 2 is hybrid-integrated by separating different types of substrates in the same optical module.

Embodiments of the present invention will be described below with reference to the drawings.
Example 1
The first embodiment exemplifies a configuration example of an optical transmitter in which an optical amplifier integrated modulator and a wavelength / polarization control circuit are integrated in a hybrid manner. FIG. 2 illustrates the configuration of the optical amplifier integrated modulator 100 in the optical transmitter according to the first embodiment of the invention. FIG. 2 shows a first input / output waveguide 102, an optical amplifier (SOA) 103 connected to the first input / output waveguide 102, a reflector 104 connected to the SOA 103, and a connection to the reflector 104. 1 × 2 coupler 105, a first optical modulator 106 ₁ connected to one of the output ends of 1 × 2 coupler 105, and a second optical modulator connected to the other of the output ends of 1 × 2 coupler 105. an optical modulator 106 _2, the first output waveguide 107 ₁ connected to the first optical modulator 106 _1, the second output waveguide 107 ₂ is connected to the second optical modulator 106 ₂ The optical amplifier integrated modulator 100 is shown monolithically integrated on the first substrate 101.

Light incident from the first input / output waveguide 101 is amplified by the SOA 102. Part of the light amplified by the SOA 102 is reflected by the reflector 104, passes through the SOA 102 again, and is emitted from the input / output waveguide 101. On the other hand, the light transmitted through the reflector 104 is branched into two by the 1 × 2 coupler 105 and is output to the first optical modulator 106 ₁ and the second optical modulator 106 ₂ , respectively. The first modulated light and the second modulated light generated by being modulated by the first optical modulator 106 ₁ and the second optical modulator 106 ₂ , respectively, are the first output waveguide 107 ₁ and The light is emitted from the first substrate 101 via the second output waveguide 107 ₂ .

FIG. 3 illustrates the configuration of the wavelength / polarization control circuit 200 in the optical transmitter according to the first embodiment of the invention. 3 shows a second output waveguides 202, a wavelength filter circuit 203 connected to the second input and output waveguides 202, a first input waveguide 204 _1, the second input waveguide 204 ₂ , a polarization rotator 205 connected to the first input waveguide 204 ₁ , a polarization multiplexer 206 connected to the second input waveguide 204 ₂ and the polarization rotator 205, A wavelength / polarization control circuit 200 in which a multiplexed light output waveguide 207 connected to a multiplexer 206 and a second substrate 201 are monolithically integrated is shown.

The first modulated light output from the first output waveguide 107 ₁ and input to the polarization rotator 205 via the _first input waveguide 204 ₁ is polarized by the polarization rotator 205. Rotate. In general, since the polarization multiplexing transmitter uses orthogonal polarization, the polarization rotation amount is set to 90 °. Light polarized wave is entered from the input of the rotating light and second waveguide ₂₀₄₂ by the polarization rotator 205 are multiplexed is input to the polarization multiplexer 206, the multiplexed light multiplexed light output waveguides The light is emitted from the second substrate 201 through the waveguide 207.

The modulated light output from the second output waveguide 107 ₂ and incident on the second input / output waveguide 202 is input to the wavelength filter circuit 203. The wavelength filter circuit 203 is designed to select light having a specific wavelength from the input light and return it to the second input / output waveguide 202 side, and transmit light of other wavelengths.

  FIG. 4 shows a specific configuration example of the wavelength filter circuit 203. 4 shows a second input / output waveguide 202, a ring resonator 208 provided near the second input / output waveguide 202, a waveguide 209 provided near the ring resonator 208, and a waveguide. A wavelength filter circuit 203 including a ring resonator 210 provided near 209, a waveguide 211 provided near the ring resonator 210, and a reflector 212 connected to one end of the waveguide 211 is shown. ing. As shown in FIG. 4, in this embodiment, a ring resonator type wavelength filter in which two ring resonators 208 and 209 are integrated is used as the wavelength filter circuit 203.

  The light input from the second input / output waveguide 202 to the wavelength filter circuit 203 propagates through the second input / output waveguide 202 and reflects a characteristic of the ring resonator 208 to have a part of light having a specific wavelength. Only light is coupled to the waveguide 209, and the remaining wavelength light passes through the wavelength filter circuit 203. Further, the light coupled to the waveguide 209 reflects the characteristics of the ring resonator 210 and only a part of the light having a specific wavelength is coupled to the waveguide 211. The light coupled to the waveguide 211 is reflected by the reflector 212, returns to the previous path, and is output from the second input / output waveguide 202 again. Therefore, when the resonance wavelength periods of the two ring resonators are different, light having a wavelength that matches the resonance wavelength is selectively reflected to the second input / output waveguide 202.

  In the present embodiment, the ring resonator is selected as the wavelength filter as shown in FIG. 4, but it may be a diffraction grating such as a distributed reflector.

  Since the SOA 102 needs to be monolithically integrated, the first substrate 101 may be another compound semiconductor such as GaAs as long as it is a material having optical gain, but in this embodiment, the laser oscillation wavelength is light. InP was selected that had the lowest loss of 1.55 μm in the fiber.

  The second substrate 201 is preferably made of a material that can accurately produce passive elements such as polarization control and wavelength selection filter in a small size. In this embodiment, the second substrate 201 is selected from silicon capable of producing a passive element in a small size with high processing accuracy and high refractive index by a sophisticated silicon process as typified by recent silicon photonics. However, glass-based materials that can produce passive elements with very low loss and high performance may be used.

  In this embodiment, an etched mirror type reflector that reflects a part of power to light by cutting the middle of the semiconductor waveguide by etching is adopted as the reflector 104 in this embodiment. However, the mechanism is not limited as long as a function of transmitting light having an oscillation wavelength in a single wavelength oscillation laser LD described later to the 1 × 2 coupler 105 and reflecting light of other wavelengths can be realized.

As the first optical modulator 106 ₁ and the second optical modulator 106 ₂ , in this embodiment, as described in Non-Patent Document 1, a nest in which two Mach-Zehnder interference waveguides are integrated as an optical modulator is used. Adopt type optical modulator. However, as described in Non-Patent Document 2, a modulator that can place a signal on light, such as an electro-absorption optical modulator that realizes on / off of light intensity by transmission / absorption of light. Any configuration is acceptable. Nested optical modulators function as so-called optical vector modulators that can modulate the phase of the electric field vector of light, and electroabsorption optical modulators have the advantage of small size, both of which can be fabricated on compound semiconductors .

FIG. 5 illustrates the configuration of the optical transmitter according to the first embodiment in which the optical amplifier integrated modulator 100 and the wavelength / polarization control circuit 200 are integrated in a hybrid manner. FIG. 5 shows an optical transmitter in which an optical amplifier integrated modulator 100, a wavelength / polarization control circuit 200, and first to third lenses 301 _{1 to} 301 ₃ are hybrid-integrated in the same optical module. It is shown. As shown in FIG. 5, between the first input / output waveguide 102 of the optical amplifier integrated modulator 100 and the second input / output waveguide 202 of the wavelength / polarization control circuit 200, the first input / output waveguide 102 is provided. the first lens ₃₀₁₁ is provided for coupling the output waveguide 102 and the second input and output waveguides 202 optically. Further, between the first output waveguide 107 ₁ of the optical amplifier integrated modulator 100 and the first input waveguide 204 ₁ of the wavelength / polarization control circuit 200, the first output waveguide 107 ₁ and the _first output waveguide 107 ₁ are connected. A second lens 301 ₂ is provided for optically coupling _one input waveguide 204 ₁ to the second output waveguide 107 ₂ of the optical amplifier integrated modulator 100 and the wavelength / polarization control circuit 200. between the second input waveguide 204 _2, third lens 301 ₃ which binds to a second output waveguide 107 ₂ and a second input waveguide 204 ₂ optically is provided.

  In general, the SOA 103 not only amplifies light but also emits light in a certain wavelength range as spontaneous emission light as so-called seed light for laser oscillation, and therefore the first input / output waveguide 102 and the second input / output waveguide are used. If the waveguide 202 is optically coupled, positive feedback is applied to light of a specific wavelength among the above-described seed light, so that the SOA 103 and the reflector 104 on the first substrate 101, and the second A single wavelength oscillation laser LD is constituted by the wavelength filter circuit 203 on the substrate 201.

Similarly, the first output waveguide 107 ₁ and the first input waveguide 204 ₁ , and the second output waveguide 107 ₂ and the second input waveguide 204 ₂ are respectively connected to the second lens 301 ₂ and the _second input waveguide 204 ₂ . if optically coupled via a third lens 301 _3, after the first modulated light polarized light outputted from the first optical modulator 106 ₁ is rotated 90 ° by the polarization rotator 205 the first modulated light and the second of the second polarization multiplex signal and the modulated light can be multiplexed by the polarization multiplexer 206 output from the optical modulator 106 ₂ to which the polarization is rotated Can be emitted from the multiplexed light output waveguide 207.

Here, the first input / output waveguide 102, the first output waveguide 107 _1, and the second output waveguide 107 ₂ can be arranged on the same cut surface of the first substrate 101. Thereby, the input / output light in the first input / output waveguide 102 and the first modulated light and the second modulated light output from the first output waveguide 107 ₁ and the second output waveguide 107 _2. Each optical axis of light is directed in the same direction. Similarly, the second input / output waveguide 202, the first input waveguide 204 _1, and the second input waveguide 204 ₂ can be disposed on the same cut surface of the second substrate 201. As a result, the optical axes of the light input and output from the respective waveguides of the second substrate 201 are directed in the same direction. Therefore, if the first substrate 101 and the second substrate 201 are arranged, the waveguides can be arranged so that the optical axes of the light from the respective waveguides are coupled.

Further, in the present embodiment, as shown in FIG. 5, it is assumed one, the first lens system with respect to the optical axis respectively as the first to third lens 301 ₁ to 301 ₃ for optical coupling However, two or more lenses may be used as necessary from the viewpoint of manufacturing accuracy and the like.

  As described above, in the present invention, the optical modulator and the optical amplifier are formed on the first substrate 101 using the compound semiconductor material, while the second material using the silicon or glass-based material that is relatively easy to process. The wavelength filter circuit 203, the polarization rotator 205, and the polarization multiplexer 206 are formed on the substrate 201, and the first substrate 101 and the second substrate 201 on which these are formed are hybrid-integrated on the same module. doing. Thereby, in an optical transmitter in which an optical modulator using a compound semiconductor is integrated, a passive optical element for polarization control and wavelength control can be formed by a simpler method compared to the conventional method. Further downsizing and higher performance of the modulator made of semiconductor can be realized.

(Example 2)
FIG. 6 illustrates the configuration of the optical transmitter according to the second embodiment of the invention. In FIG. 6, the optical amplifier integrated modulator 100, the wavelength / polarization control circuit 200, and the first to third spot size converters 401 _{1 to} 401 ₃ are hybrid-integrated in the same optical module. An optical transmitter is shown. As shown in FIG. 6, the end of the first input / output waveguide 102 of the optical amplifier integrated modulator 100 and the end of the second input / output waveguide 202 of the wavelength / polarization control circuit 200 are first spot size converter 401 ₁ for coupling one of the input and output waveguides 102 and second output waveguides 202 optically is provided. Further, the first output waveguide 107 is connected to the end of the first output waveguide 107 ₁ of the optical amplifier integrated modulator 100 and the end of the first input waveguide 204 ₁ of the wavelength / polarization control circuit 200. ₁ and the first input waveguide 204 ₁ are optically coupled to each other, and a _second spot size converter 401 ₂ is provided, and the end of the second output waveguide 107 ₂ of the optical amplifier integrated modulator 100 is provided. And a second input waveguide 107 ₂ and a second input waveguide 204 ₂ are optically coupled to the end of the second input waveguide 204 ₂ of the wavelength / polarization control circuit 200. It is provided spot size converter 401 _3.

In the first embodiment, the optical amplifier integrated modulator 100 and the wavelength / polarization control circuit 200 are optically coupled using the _{first to} third lenses 301 _{1 to} 301 ₃ . In the second embodiment, the spot size converters 401 that change the mode distribution guided through the waveguide are integrated on the first substrate 101 and the second substrate 201, respectively. It is possible to optically couple the waveguides of the first substrate 101 and the second substrate 201, so-called butt coupling.

  At this time, each spot size converter 401 needs to be designed so that the optical field distribution between the waveguides forming the optical coupling is close. With this configuration, a further compact hybrid integrated optical transmitter that does not require a lens can be realized.

  Here, in the second embodiment, the spot size converter 401 is provided in all the waveguides of the first substrate 101 and the second substrate 201. However, the first substrate 101 and the second substrate are provided. The spot size converter 401 may be provided in the waveguide in any one of 201.

(Example 3)
FIG. 7 illustrates the configuration of the wavelength filter circuit in the optical transmitter according to the third embodiment of the invention. 7 shows a second input / output waveguide 202, a ring resonator 208 provided in the vicinity of the second input / output waveguide 202, a waveguide 209 provided in the vicinity of the ring resonator 208, and a waveguide. 209 provided near the ring resonator 210, a waveguide 211 provided near the ring resonator 210, a reflector 212 connected to one end of the waveguide 211, and a micro provided on the ring resonator 208. A wavelength filter circuit 203 ′ including a heater 213 and a microheater 214 provided on the ring resonator 210 is shown.

  In the third embodiment, the wavelength filter circuit 203 ′ is provided with first and second micro heaters 213 and 214 which are mechanisms for changing the reflection wavelength with respect to the electric signal input to the wavelength filter circuit 203 ′. By adjusting the heat generation temperature of the first and second microheaters 213 and 214 to modulate the refractive index, the single wavelength oscillation laser part LD can be made a variable wavelength laser. As shown in the third embodiment, if the refractive index is modulated by providing the microresonators 213 and 214 in the ring resonators 208 and 209, respectively, the single-wavelength oscillation laser unit according to the change in the resonance wavelength of the ring resonator The oscillation wavelength of the LD can be controlled.

Example 4
FIG. 8 illustrates the configuration of the optical transmitter according to the fourth embodiment of the invention. FIG. 8 shows an optical transmitter in which an optical amplifier integrated modulator 100, a wavelength / polarization control circuit 800, and spot size converters 401 _{1 to} 301 ₃ are hybrid-integrated in the same optical module. ing. As shown in FIG. 8, the wavelength and polarization control circuit 800 according to the fourth embodiment is provided on the first input waveguide 204 _1, the intensity of the light first guided through the input waveguide 204 ₁ The intensity of the first modulated light that is provided between the monitor rotator 205 and the polarization rotator 205 and the multiplexer 205, and is guided between the polarization rotator 205 and the multiplexer 205. a monitor photodetector 802 for monitoring, provided on the second input waveguide 204 _2, a monitor photodetector 803 for monitoring the intensity of the second modulated light guided to the second input waveguide 204 _2, further Prepare.

  For optical transmitters, it is often necessary in applications to monitor the intensity of light in the transmitter. In the optical transmitter according to the fourth embodiment, particularly when the material of the second substrate 201 is a silicon material, the monitor photodetectors 801 to 803 can be integrated in the wavelength / polarization control circuit 800 relatively easily. . Therefore, the light intensity of the light output from the optical amplifier integrated modulator 100 can be monitored by the monitor photodetectors 801 to 803 integrated in the wavelength / polarization control circuit 800.

  In the fourth embodiment, the monitor photodetectors 801 to 803 monitor the intensity of the first modulated light, the second modulated light, and the return light from the wavelength filter circuit 203 to the optical amplifier integrated modulator 100, respectively. If necessary, as many photo detectors as necessary may be arranged. Further, for example, the first modulated light is demultiplexed on the optical amplifier integrated modulator 100 side, coupled to an appropriate waveguide of the wavelength / polarization control circuit 800, and then received by a monitor photodetector. The light path to the monitor photodetector may be changed as necessary.

(Example 5)
FIG. 9 illustrates the configuration of the optical transmitter according to the fifth embodiment of the invention. FIG. 9 shows an optical transmitter in which an optical amplifier integrated modulator 100, a wavelength / polarization control circuit 900, and spot size converters 401 _{1 to} 301 ₃ are hybrid-integrated in the same optical module. ing. As shown in FIG. 9, the wavelength and polarization control circuit 900 according to the fifth embodiment, the wavelength filter circuit 203 and a first input waveguide 204 optical hybrid circuit 901 which is connected to _a wavelength filter circuit 203 and an optical hybrid circuit which is connected to the second input waveguide 204 ₂ are provided.

In the optical transmitters according to the first to fourth embodiments, the optical path in which the light reciprocates through the single wavelength oscillation laser unit LD configured by the optical amplifier 103, the reflector 104, and the wavelength filter circuit 203 is output from the optical amplifier 103. The optical function is separated from the side, that is, the optical path passing through the first and second input waveguides 204 ₁ and 204 ₂ from the 1 × 2 coupler 105.

  However, in the optical transmitter according to the fifth embodiment, a new function is realized by combining these two optical paths in the second substrate 201 made of silicon or the like, which can easily form a relatively complicated passive element. I can do things.

For example, as shown in FIG. 9, the optical hybrid circuits 901 and 902 extract and input part of the oscillation light from the single wavelength oscillation laser part LD through the wavelength filter circuit 203, respectively, and the first and second light components. The first and second modulated lights output from the modulators 106 ₁ and 106 ₂ are input, and a part of the oscillation light and the modulated light are combined.

  In principle, the wavelengths of the light incident from the single-wavelength laser unit LD and the wavelengths of the first and second modulated light incident on the two optical hybrid circuits 901 and 902 are exactly the same. . Therefore, for example, when the first and second modulated lights are quadrature phase shift keying (QPSK), suitable hybrid elements such as 2 × 4 port multimode interference waveguides as the optical hybrid circuits 901 and 902 If the photo detector is further integrated using this, the phase information of each modulated light can be known by interference with the light output from the single wavelength oscillation laser part LD. That is, it is possible to monitor the states of the first and second modulated lights.

Optical amplifier integrated modulator 10, 100
Wavelength / polarization control circuit 20, 200
Substrate 101, 201
Waveguides 102, 107, 202, 204, 207, 209, 211
SOA 103
Reflector 104, 212
1 × 2 coupler 105
Optical modulator 106
Wavelength filter circuit 203
Polarization rotator 205
Polarization multiplexer 206
Ring resonator 208, 210
Micro heater 213, 214
Lens 301
Spot size converter 401
Monitor photo detector 801, 802, 803
Optical hybrid circuit 901, 902

Claims (8)

A hybrid integrated optical transmitter including an optical amplification modulator and a wavelength / polarization control circuit,
The optical amplification modulator includes:
A first input / output waveguide;
An optical amplifier for amplifying light input from the first input / output waveguide;
A reflector that reflects part of the amplified light output from the optical amplifier and returns the amplified light to the first input waveguide side;
A 1 × 2 coupler connected to the optical amplifier via the reflector and bifurcating amplified light input from the optical amplifier through the reflector;
A first optical modulator that generates first modulated light by modulating one of the branched lights output from the 1 × 2 coupler;
A second optical modulator that generates a second modulated light by modulating the other branched light output from the 1 × 2 coupler;
A first output waveguide for outputting the first modulated light generated by the first optical modulator;
A second output waveguide for outputting the second modulated light generated by the second optical modulator;
Is monolithically integrated on the first substrate,
The wavelength / polarization control circuit is:
A second input / output waveguide;
A wavelength filter circuit that selectively reflects light having a specific wavelength with respect to the wavelength of light incident from the second input / output waveguide and outputs the reflected light to the second input / output waveguide. When,
A first input waveguide for inputting the first modulated light output from the first output waveguide;
A second input waveguide for inputting the second modulated light output from the second output waveguide;
A polarization rotator that rotates a polarization of the first modulated light input from the first input waveguide to generate a polarization rotation light;
A polarization multiplexer that combines the second modulated light and the polarization rotation light;
A combined light output waveguide for outputting the combined light combined by the polarization multiplexer;
Is monolithically integrated on the second substrate,
The optical amplification modulator and the wavelength / polarization control circuit are integrated in the same optical module,
The optical amplifier, the single-wavelength oscillation laser unit configured to selectively oscillate only light having a specific wavelength reflecting the characteristics of the wavelength filter circuit among the naturally generated light emitted from the optical amplifier, A reflector and the wavelength filter circuit are designed,
The first substrate is made of a compound semiconductor material having an optical gain, and the second substrate is made of a material different from the first substrate. Transmitter.   2. The hybrid integrated optical transmitter according to claim 1, wherein the second substrate is made of silicon or a glass-based material. The first input / output waveguide, the first output waveguide, and the second output waveguide are each disposed on the same cut surface of the first substrate,
The second input / output waveguide, the first input waveguide, and the second input waveguide are respectively disposed on the same cut surface of the second substrate. 3. The hybrid integrated optical transmitter according to 2. A first lens for optically coupling the first input / output waveguide and the second input / output waveguide;
A second lens for optically coupling the first output waveguide and the first input waveguide;
A third lens for optically coupling the second output waveguide and the second input waveguide;
The hybrid integrated optical transmitter according to claim 1, further comprising:   Each end face of the first input / output waveguide, the first output waveguide and the second output waveguide, and / or the second input / output waveguide, the first input waveguide, and the The hybrid according to any one of claims 1 to 3, further comprising a spot size converter provided on each end face of the second input waveguide to change a mode distribution guided through the waveguide. Integrated optical transmitter.   6. The hybrid integrated optical modulator according to claim 1, wherein the wavelength filter circuit has a mechanism that changes a reflection wavelength with respect to an input electric signal.   7. The wavelength / polarization control circuit further includes a monitor photodetector for monitoring light intensity of the first modulated light and the second modulated light. 2. A hybrid integrated optical modulator according to 1. The wavelength / polarization control circuit is:
Connected to the wavelength filter circuit and the first input waveguide, and inputs a part of the oscillation light outputted from the single wavelength oscillation laser unit through the wavelength filter circuit and the first modulated light. A first optical hybrid circuit for combining a part of the inputted oscillation light and the first modulated light;
Connected to the wavelength filter circuit and the second input waveguide, and inputs a part of the oscillation light outputted from the single wavelength oscillation laser unit through the wavelength filter circuit and the second modulated light. A second optical hybrid circuit for combining a part of the inputted oscillation light and the second modulated light;
The hybrid integrated optical modulator according to claim 1, further comprising: