JP2006084546A - Light transmitting and receiving device and optical communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the occurrence of crosstalk being unique to a one-fiber and bidirectional full-duplex optical fiber communication. <P>SOLUTION: A light transmitting and receiving device 1a which performs the one-fiber and bidirectional full-duplex optical fiber communication by being connected with an optical fiber 6 is characterized in that the position of the light-entering and exiting end face 6a of the optical fiber 6 is arranged by being shifted in the direction of the optical axis with respect to the focal position of the transmitting light emitted from a light emitting element 2, and that the focal position of return light which is emitted from the light emitting element 2 and which is reflected at the light-entering and exiting end face 6a of the optical fiber 6 is made to differ from the focal position of receiving light to be emitted from the light-entering and exiting end face 6a of the optical fiber 6, and that a light receiving element 3 is arranged where the return light is out of a position in which it is converged and the element 3 is within the light receiving range of receiving light. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical transmission / reception apparatus and an optical communication system that perform single-core bidirectional full-duplex optical fiber communication. Specifically, the crosstalk is reduced by preventing the light emitted from the light emitting means and reflected by the light incident / exit end face of the optical fiber from being condensed on the light receiving means.

  FIG. 8 is an explanatory diagram showing a schematic configuration example of an optical communication system that performs single-core bidirectional full-duplex optical fiber communication. In this optical communication system 100, an optical transmission / reception apparatus 103 including a light emitting element 101 and a light receiving element 102 is connected by a single optical fiber 104.

  When data is transmitted from one optical transceiver 103A to the other optical transceiver 103B, transmission light is emitted from the light emitting element 101 of the optical transceiver 103A. The transmission light emitted from the light emitting element 101 of the optical transceiver 103A is transmitted through the optical fiber 104 and received by the light receiving element 102 of the optical transceiver 103B.

  When data is transmitted from the other optical transmission / reception device 103B to one optical transmission / reception device 103A, transmission light is emitted from the light emitting element 101 of the optical transmission / reception device 103B. The transmission light emitted from the light emitting element 101 of the optical transmission / reception device 103B is transmitted through the optical fiber 104 used when data is transmitted from the optical transmission / reception device 103A, and is received by the light receiving element 102 of the optical transmission / reception device 103A.

  As described above, a technique of simultaneously transmitting and receiving with one optical transmission / reception apparatus 103A and the other optical transmission / reception apparatus 103B using a single-core optical fiber 104 is called single-core bidirectional full-duplex optical fiber communication or the like. .

  Now, in order to perform single-core bi-directional full-duplex optical fiber communication, the transmission light emitted from the light emitting element 101 is guided to the optical fiber 104, and the reception light emitted from the optical fiber 104 is guided to the light receiving element 102. The optical transmitter / receiver 103 is necessary. As an optical transmitter / receiver having such a function, there is a configuration using a beam splitter (see, for example, Patent Document 1).

  FIG. 9 is a plan view showing a schematic configuration example of a conventional optical transceiver having a beam splitter. The optical transmission / reception apparatus 103 starts up the transmission light from the light emitting element 101 with a beam splitter 107 having a transmittance of about 50% and a reflectance of about 50%, and condenses it on the end face of the optical fiber 104 with a lens 108.

  The received light from the optical fiber 104 is condensed by the lens 108 used at the time of transmission, transmitted through the beam splitter 107, and coupled to the light receiving element 102. In FIG. 9, transmission light is indicated by a solid line, and reception light is indicated by a broken line.

  In the optical transmission / reception apparatus 103 using the beam splitter 107, the optical axes of the transmission light and the reception light are the same. Therefore, a lens 108 can be disposed near the end face of the optical fiber 104 to collect both the transmission light and the reception light. . Therefore, the transmission efficiency of incident light from the light emitting element 101 to the optical fiber 104 and the reception efficiency from the optical fiber 104 to the light receiving element 102 are increased.

JP-A-8-166527

  However, in the conventional optical transmission / reception apparatus 103 using the beam splitter 107, the light emitted from the light emitting element 101 and reflected by the incident / exit end face of the optical fiber 104 is collected by the lens 108 and coupled to the light receiving element 102. Therefore, there is a drawback that large crosstalk peculiar to single-core bidirectional full-duplex optical fiber communication occurs.

  FIG. 10 is an explanatory diagram showing the principle of occurrence of crosstalk. In FIG. 10, S is signal light (received light) from an optical transmission / reception apparatus not shown here. The transmission light emitted from the light emitting element 101 is reflected by the beam splitter 107, collected by the lens 108, and enters from the incident / exit end face of the optical fiber 104.

  A part of the transmitted light emitted from the light emitting element 101 is reflected by the incident / exit end face of the optical fiber 104. However, since the optical axes of the transmitted light and the received light are the same, the reflected return light is collected by the lens 108. The light is received and coupled to the light receiving element 102. This is crosstalk (return light) N.

  FIG. 11 is an explanatory view showing a relationship between a light receiving surface of a conventional light receiving element and received light and return light. In the conventional optical transceiver 103, the optical axes of the transmitted light and the received light are the same. Therefore, in the configuration in which the received light is collected on the light receiving surface 102a of the light receiving element 102, the transmitted light is transmitted at the incident / exit end surface of the optical fiber 104. The reflected return light is also condensed on the light receiving surface 102 a of the light receiving element 102.

  An example of calculating the S / N (signal-to-noise ratio) of a conventional optical transmission / reception apparatus using a beam splitter is shown in equation (1) below. In the following calculation, the transmittance of the beam splitter was 0.5 and the reflectance of the beam splitter was 0.5.

here,
P ₁ : intensity of the light emitting element P ₂ : fiber emission intensity a: coupling efficiency of the received light with the light receiving element b: reflectivity of the fiber entrance / exit end face c: coupling efficiency of the return light on the fiber entrance / exit end face with the light receiving element is there.

  When all the received light is coupled to the light receiving element, a = 1, and when a fluorine-based plastic fiber having a refractive index of about 1.35 is used for the optical fiber, b = 0.024. Furthermore, when all the return light at the end face of the optical fiber is coupled to the light receiving element, c = 1.

Thus, the received light S and the crosstalk N are
S = 0.5aP ₂ = 0.5P ₂
N = 0.5 × 0.5bcP ₁ = 5.8 × 10 ⁻³ P ₁
So,
S / N = 86P ₂ / P ₁ (1)
It is.

In order to achieve a bit error rate BER <10 ⁻¹² in single-core two-way communication in the giga band, S / N> 10 is usually required, and thus the allowable loss is expressed by the following equation (2): Indicated by
P ₂ / P ₁ > 0.12 (−9.2 dB) (2)

  According to Equation (2), only 9.2 dB loss is allowed from the light emitting element to the fiber exit end. Since the beam splitter causes a loss of 3 dB up to the fiber incident end, the remaining 6.2 dB is a loss allowed for the fiber.

  For example, considering that a fiber is laid using a fluorine-based plastic fiber having a transmission loss of 4 dB / 100 m, a bending loss of 0.2 dB / 90 °, and an allowable radius of curvature R = 20 mm, bending is performed 11 times at 100 m. Only allowed. This is a major constraint on laying. For example, in a laying environment where bending of 12 times or more is required, S / N> 10 cannot be secured, and giga-band single-core bidirectional communication may be difficult. Recognize.

  The present invention has been made to solve such a problem, and an object thereof is to provide an optical transmission / reception apparatus and an optical communication system in which crosstalk is reduced.

  In order to solve the above-described problems, an optical transmission / reception apparatus according to the present invention is an optical transmission / reception apparatus that is connected to an optical fiber and performs single-core bidirectional full-duplex optical fiber communication. And a light collecting means for condensing the transmission light emitted from the light emitting means on the incident / exit end face of the optical fiber and condensing the received light emitted from the incident / exit end face of the optical fiber on the light receiving means, The optical path separating means for guiding the transmitted light to the incident / exit end face of the optical fiber and the received light to the light receiving means, and the focal point of the return light emitted from the light emitting means and reflected by the incident / exit end face of the optical fiber. And a return light reflecting means for making the position different from the focus position of the received light emitted from the incident / exit end face of the optical fiber, and the light receiving means is at a position deviated from the focus of the returned light and receives the received light. Also placed within the range It is.

  An optical communication system according to the present invention includes the above-described optical transmission / reception device. In an optical communication system in which optical transmission / reception devices are connected to each other through an optical fiber to perform one-core bidirectional full-duplex optical fiber communication, The light emitting means for emitting the transmission light, the light receiving means for receiving the received light, and the transmission light emitted from the light emitting means are condensed on the incident / exit end face of the optical fiber and emitted from the incident / exit end face of the optical fiber. Light collecting means for condensing the received light on the light receiving means, light path separating means for guiding the transmitted light to the incident / exit end face of the optical fiber, and light receiving light to the light receiving means, and light emitted from the light emitting means. A return light reflecting means for making the position of the focal point of the return light reflected by the incident / exit end face of the fiber different from the position of the focal point of the received light emitted from the incident / exit end face of the optical fiber, Out of focus In location, and, in which it was placed in the light receiving range of the receiving light.

  According to the optical transmitter / receiver and the optical communication system according to the present invention, the signal light (transmitted light) emitted from the light emitting means is guided to the optical fiber by the optical path separating means, and condensed by the light collecting means. The light enters the input / output end face of the fiber.

  The transmission light incident from the incident / exit end face of the optical fiber is propagated through the optical fiber and emitted from the other incident / exit end face. The signal light (received light) emitted from the incident / exit end face of the optical fiber is collected by the light collecting means and guided to the light receiving means by the optical path separating means.

  In single-core bidirectional full-duplex optical fiber communication, transmission / reception is performed simultaneously between optical transmission / reception devices connected by a single-core optical fiber.

  Here, a part of the transmission light emitted from the light emitting means is reflected by the incident / exit end face of the optical fiber. The return light reflected by the incident / exit end face is condensed at a position different from the focal position of the received light by the return light reflecting means, so that the spot diameter of the received light is the return light on the return light collecting surface. Larger than the spot diameter.

  As a result, the light receiving means is disposed at a position within the light receiving range of the received light by removing the position where the return light is collected, and the received light is received by the light receiving means, whereas the return light is received. Since the light is not condensed on the means, it is not received by the light receiving means, and crosstalk is reduced.

  According to the optical transmission / reception apparatus of the present invention, the light receiving means is disposed at a position where the transmitted light emitted from the light emitting means of the own apparatus does not receive the return light due to reflection by the incident / exit end face of the optical fiber. Can be reduced.

  As a result, a high S / N ratio can be achieved in an optical transmission / reception apparatus that performs single-core bidirectional full-duplex optical fiber communication, and loss allowed for the optical fiber can be greatly reduced.

  Therefore, according to the optical communication system equipped with such an optical transmission / reception apparatus, the constraints on installation due to the bending and length of the optical fiber are greatly relaxed, and the single-core bidirectional in the giga band regardless of the installation conditions. Full duplex optical fiber communication can be realized.

  Embodiments of an optical transmission / reception apparatus and an optical communication system according to the present invention will be described below with reference to the drawings.

  FIG. 1 is a plan view showing a schematic configuration example of the optical transmission / reception apparatus according to the first embodiment. The optical transmitter / receiver 1a according to the first embodiment includes a light emitting element 2 that emits transmission light, a light receiving element 3 that receives reception light, a lens 4 that collects transmission light and reception light, and transmission light and reception. A beam splitter 5 for separating light is provided and connected to an optical fiber 6.

  The optical transmitter / receiver 1a condenses the position where the received light (S) emitted from the incident / exit end face 6a of the optical fiber 6 is condensed and the return light (N) reflected by the incident / exit end face 6a of the optical fiber 6. The position is shifted in the optical axis direction of the optical fiber 6. As a result, the light receiving element 3 can be adjusted to a position where no return light is received, thereby reducing crosstalk.

  The light emitting element 2 is an example of a light emitting means, and is composed of, for example, a laser diode. The light receiving element 3 is an example of a light receiving means, and is composed of, for example, a photodiode. The lens 4 is an example of a condensing unit, and condenses the transmission light emitted from the light emitting element 2 on the incident / exit end face 6a of the optical fiber 6 and diffuses and emits the received light from the incident / exit end face 6a of the optical fiber 6. Is condensed and coupled to the light receiving element 3.

  The beam splitter 5 is an example of an optical path separating unit, and is composed of, for example, a half mirror having a transmittance of about 50% and a reflectance of about 50%. The beam splitter 5 is provided at an inclination angle of 45 degrees on the optical axis of the lens 4, reflects the transmission light emitted from the light emitting element 2, guides it to the incident / exit end face 6 a of the optical fiber 6, and the optical fiber 6. The received light emitted from the incident / exit end face 6 a is transmitted and guided to the light receiving element 3.

  The optical fiber 6 is a fluorine plastic fiber, for example, and is connected to the optical transceiver 1a by a connector or the like (not shown). In the optical transceiver 1a, the optical fiber 6 is connected so that the optical axis of the lens 4 and the optical axis of the optical fiber 6 coincide.

  FIG. 2 is a schematic configuration diagram showing an example of an embodiment of an optical communication system provided with the optical transceiver 1a. The optical communication system 11 is formed by connecting the optical communication apparatuses 1a with each other through a single-core optical fiber 6.

  Transmitted light emitted from the light emitting element 2 of the first optical transmission / reception device 1 a connected to one end of the optical fiber 6 is reflected by the beam splitter 5, and is input / output end face of the optical fiber 6 by the lens 4. Condensed to 6a.

  The transmission light incident from one incident / exit end face 6 a of the optical fiber 6 is propagated through a core (not shown) of the optical fiber 6 and is emitted from the other incident / exit end face 6 a of the optical fiber 6. The second optical transmission / reception device 1a is connected to the other end of the optical fiber 6, and the received light emitted from the other incident / exit end surface 6a of the optical fiber 6 is transmitted through the lens 4 in the second optical transmission / reception device 1a. The condensed light passes through the beam splitter 5 and is coupled to the light receiving element 3.

  Similarly, the transmission light emitted from the light emitting element 2 of the second optical transmission / reception device 1a is reflected by the beam splitter 5 and condensed on the other incident / exit end face 6a of the optical fiber 6 by the lens 4.

  The transmission light incident from the other incident / exit end face 6 a of the optical fiber 6 is propagated through a core (not shown) of the optical fiber 6 and is emitted from one incident / exit end face 6 a of the optical fiber 6. Received light emitted from one incident / exit end face 6 a of the optical fiber 6 is collected by the lens 4 in the first optical transmitter / receiver 1 a, passes through the beam splitter 5, and is coupled to the light receiving element 3.

  In the optical communication system 11 that performs the single-core bidirectional full-duplex optical fiber communication, the first optical transmission / reception device 1a and the second optical transmission / reception device 1a perform transmission / reception simultaneously.

  Here, part of the transmission light emitted from the light emitting element 2 is reflected by the incident / exit end face 6 a of the optical fiber 6. The return light reflected by the incident / exit end face 6 a of the optical fiber 6 is collected by the lens 4, passes through the beam splitter 5, and is guided toward the light receiving element 3.

  Then, the received light emitted from the optical transmission / reception apparatus 1a of the connection partner and emitted from the incident / exit end face 6a of the optical fiber 6 is received, and the return light of the own apparatus reflected by the incident / exit end face 6a is not received. By providing return light reflecting means for reflecting the return light so that the light receiving element 3 can be adjusted, crosstalk between the received light and the return light is reduced.

In other words, when the optical fiber 6 is connected, the optical transmission / reception apparatus 1a has a length from the lens 4 to the incident / exit end face 6a of the optical fiber 6 as shown in FIG. It is shorter than the focal length f _{1, and} is configured such that the focal position F ₁ of the transmitted light is located deeper in the optical axis direction than the incident / exit end face 6 a of the optical fiber 6.

As a result, the focal length f _{2 of the} received light that is emitted from the incident / exit end face 6 a of the optical fiber 6 and collected by the lens 4 is reflected by the incident / exit end face 6 a of the optical fiber 6 and condensed by the lens 4. The focal length f _{3 of the} returned light is shortened.

Therefore, on the light receiving element 3 side, the focal position F ₃ of the return light is in front of the optical fiber 6 in the optical axis direction with respect to the lens 4 from the focal position F ₂ of the received light, and is perpendicular to the optical axis of the optical fiber 6. On the return light condensing surface M where the spot diameter of the return light is the smallest, the spot diameter of the received light is larger than the spot diameter of the return light.

  FIG. 3 is an explanatory diagram showing the relationship between the light receiving surface of the light receiving element and the spot diameters of received light and return light. As shown in FIG. 1, on the return light condensing surface M where the spot diameter of the return light is the smallest, the spot diameter of the received light is larger than the spot diameter of the return light. The light receiving element 3 can be adjusted so that the light receiving surface 3a does not receive the return light and receives the received light.

  In the optical transmitter / receiver 1a, since the received light is not condensed on the light receiving surface 3a of the light receiving element 3, the coupling efficiency between the light receiving element 3 and the received light is 100% or less, but the return at the incident / exit end face 6a of the optical fiber 6 is reduced. The coupling efficiency between the light and the light receiving element 3 can be 0%.

  An example of calculating the S / N ratio of the optical transmission / reception device 1a according to the first embodiment is shown in Expression (3) below. In the following calculation, the transmittance of the beam splitter 5 was 0.5, and the reflectance of the beam splitter 5 was 0.5.

here,
P ₁ : intensity of the light emitting element P ₂ : fiber emission intensity a: coupling efficiency of the received light with the light receiving element b: reflectivity of the fiber entrance / exit end face c: coupling efficiency of the return light on the fiber entrance / exit end face with the light receiving element is there.

  Since the received light is not collected on the light receiving surface 3a of the light receiving element 3, a = 0.12. When a fluorine-based plastic fiber having a refractive index of about 1.35 is used as the optical fiber 6, b = 0.023. Furthermore, c = 0 by adjusting the light receiving element 3 to a position where it does not receive return light.

Thus, the received light S and the crosstalk N are
S = 0.5aP ₂ = 0.15P ₂
N = 0.5 × 0.5bcP ₁ = 0
So,
S / N = ∞ (3)
It is.

In order to achieve a code error rate BER <10 ⁻¹² in single-core two-way communication in the giga band, S / N> 10 is usually required. However, in the optical transmission / reception apparatus 1a, the intensity P of the light emitting element 2 is required. _It can be seen that S / N> 10 can always be secured regardless of ₁ .

  In the conventional method, the loss allowed in the optical fiber is limited to about 6 dB. However, in this example, since S / N = ∞, it is necessary to limit the loss in the optical fiber due to crosstalk. Absent.

  Therefore, also in the single-core bidirectional full-duplex optical fiber communication, the same crosstalk as that in the two-core bidirectional optical fiber communication is expected to be relaxed, and the restrictions on the installation due to bending and fiber length are greatly eased.

FIG. 4 is a plan view illustrating a schematic configuration example of the optical transmission / reception apparatus according to the second embodiment. In the optical transceiver 1b of the second embodiment, when the optical fiber 6 is connected, the length from the lens 4 to the incident / exit end face 6a of the optical fiber 6 is the focal point of the transmission light condensed by the lens 4. It is longer than the distance f _{1 and} is configured such that the focal position F ₁ of the transmitted light is a position before the incident / exit end face 6 a of the optical fiber 6 in the optical axis direction.

As a result, the focal length f _{2 of the} received light that is emitted from the incident / exit end face 6 a of the optical fiber 6 and collected by the lens 4 is reflected by the incident / exit end face 6 a of the optical fiber 6 and condensed by the lens 4. the focal length f ₃ of the return light becomes longer.

Therefore, on the light receiving element 3 side, the focal position F ₃ of the return light is located behind the lens 4 in the optical axis direction of the optical fiber 6 with respect to the focal position F ₂ of the received light, and as in the first embodiment, On the return light condensing surface M perpendicular to the optical axis of the optical fiber 6 and having the smallest spot diameter of the return light, the spot diameter of the received light is larger than the spot diameter of the return light.

  Therefore, as shown in FIG. 3, the light receiving surface 3a of the light receiving element 3 can be adjusted so that the light receiving surface 3a does not receive the return light and the received light is received. The coupling efficiency between the return light and the light receiving element 3 at the light incident / exit end face 6a can be reduced to 0%.

FIG. 5 is a plan view showing a schematic configuration example of the optical transmission / reception apparatus according to the third embodiment. Similarly to the optical transmission / reception apparatus 1a of the first embodiment, the optical transmission / reception apparatus 1c of the third embodiment is connected from the lens 4 to the incident / exit end face 6a of the optical fiber 6 when the optical fiber 6 is connected. The length is shorter than the focal length f _{1 of the} transmission light collected by the lens 4, and the focal position F ₁ of the transmission light is a position that enters the depth in the optical axis direction from the incident / exit end face 6 a of the optical fiber 6. Configured as follows.

  Further, the optical axis of the optical fiber 6 is configured to be shifted parallel to the optical axis of the lens 4.

  If the optical axis of the optical fiber 6 is deviated from the optical axis of the lens 4, the center of the optical fiber 6 is deviated from the optical axis of the transmission light collected by the lens 4, and the incident / exit end face 6 a of the optical fiber 6 is changed. Transmitted light is incident on a position deviated from the center.

  Since the reception light emitted from the optical fiber 6 is emitted from the center of the incident / exit end face 6 a, the optical axis of the reception light incident on the lens 4 is shifted from the center and collected by the lens 4 is the light of the lens 4. Tilt relative to the axis.

  As a result, the center of the reception light emitted from the connection optical transmission / reception apparatus (not shown) and emitted from the incident / exit end face 6a of the optical fiber 6 and the center of the return light of the transmission light of the own apparatus reflected by the incident / exit end face 6a are obtained. Shift.

  Therefore, on the return light condensing surface M where the spot diameter of the return light is the smallest, the spot diameter of the received light is larger than the spot diameter of the return light, and the center of the spot of the return light and the center of the spot of the received light are To be separated.

  FIG. 6 is an explanatory diagram showing the Gaussian distribution of the received light and the relationship between the spot of the received light and the return light on the light receiving surface of the light receiving element. In the optical transmission / reception device 1c, as shown in FIG. 6A, the light receiving surface 3a of the light receiving element 3 does not receive the return light, receives the received light, and has a strong Gaussian distribution. The light receiving element 3 can be adjusted so as to be positioned at the center of the light receiving element 3.

  Thereby, compared with the optical transmission / reception apparatus of 1st Embodiment and 2nd Embodiment, the coupling efficiency of the light receiving element 3 and received light can be enlarged.

  Further, by adjusting the distance between the optical axis of the transmitted light and the center of the optical fiber 6, the return light and the received light are completely separated as shown in FIG. The light-receiving element 3 can be adjusted so that the light-receiving surface 3a is positioned at the center of the Gaussian distribution having a strong.

FIG. 7 is a plan view showing a schematic configuration example of the optical transmission / reception apparatus according to the fourth embodiment. Similarly to the optical transmission / reception apparatus 1a of the first embodiment, the optical transmission / reception apparatus 1d of the fourth embodiment is connected from the lens 4 to the incident / exit end face 6a of the optical fiber 6 when the optical fiber 6 is connected. The length is shorter than the focal length f _{1 of the} transmission light collected by the lens 4, and the focal position F ₁ of the transmission light is a position that enters the depth in the optical axis direction from the incident / exit end face 6 a of the optical fiber 6. Configured as follows.

  Further, the return light reflected by the incident / exit end face 6a of the optical fiber 6 is inclined, for example, on the incident / exit end face 6a of the optical fiber 6 so that it is inclined with respect to the received light emitted from the incident / exit end face 6a of the optical fiber 6. The optical axis of incident transmission light is tilted.

  In order to tilt the optical axis of the transmission light, for example, the tilt of the beam splitter 5 with respect to the optical axis of the optical fiber 6 is made larger or smaller than 45 degrees.

  When the optical axis of the transmission light is tilted, the optical axis of the return light reflected by the incident / exit end face 6a of the optical fiber 6 is tilted. Further, the transmission light is incident on the incident / exit end face 6 a of the optical fiber 6 at a position shifted from the center.

  Since the optical axis of the reception light emitted from the incident / exit end face 6 a of the optical fiber 6 is substantially parallel to the optical axis of the optical fiber 6, the optical axis is emitted from a not-shown optical transmission / reception device to be connected. The optical axis of the return light of the transmission light of the own apparatus reflected by the incident / exit end face 6a is inclined with respect to the optical axis of the reception light emitted from 6a.

  Thereby, in the return light condensing surface M where the spot diameter of the return light is the smallest, the center of the reception light is shifted from the center of the return light, and the spot diameter of the reception light is larger than the spot diameter of the return light.

  Therefore, in the optical transmitter / receiver 1d, as shown in FIGS. 6A and 6B, the light receiving surface 3a of the light receiving element 3 does not receive the return light, receives the received light, and receives the received light. The light receiving element 3 can be adjusted so as to be positioned at the center of the Gaussian distribution having a high intensity of.

  Thereby, compared with the optical transmission / reception apparatus of 1st Embodiment and 2nd Embodiment, the coupling efficiency of the light receiving element 3 and received light can be enlarged.

  Since the optical axis of the return light is tilted with respect to the optical axis of the received light, the light emitting element 2 or the lens 4 may be tilted in order to tilt the optical axis of the transmitted light. In addition, the optical axis of the return light can be inclined with respect to the optical axis of the received light also by inclining the incident / exit end face 6 a of the optical fiber 6. In this case, the optical axis of the transmission light may not be inclined.

  The present invention can be applied to an optical communication network built in a home or office because an optical transceiver having reduced crosstalk can be provided at low cost.

It is a top view which shows the schematic structural example of the optical transmission / reception apparatus of 1st Embodiment. It is a schematic block diagram which shows an example of embodiment of an optical communication system. It is explanatory drawing which shows the relationship between the light-receiving surface of a light receiving element, and the spot diameter of received light and return light. It is a top view which shows the schematic structural example of the optical transmission / reception apparatus of 2nd Embodiment. It is a top view which shows the schematic structural example of the optical transmission / reception apparatus of 3rd Embodiment. It is explanatory drawing which shows the relationship between the Gaussian distribution of received light, and the spot of the received light and return light in the light-receiving surface of a light receiving element. It is a top view which shows the schematic structural example of the optical transmission / reception apparatus of 4th Embodiment. It is explanatory drawing which shows the schematic structural example of the optical communication system which performs single core bidirectional | two-way full duplex optical fiber communication. It is a top view which shows the schematic structural example of the conventional optical transmitter / receiver. It is explanatory drawing which shows the generation | occurrence | production principle of crosstalk. It is explanatory drawing which shows the relationship between the light-receiving surface of the conventional light receiving element, received light, and return light.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a ... Optical transmitter / receiver, 2 ... Light emitting element, 3 ... Light receiving element, 3a ... Light receiving surface, 4 ... Lens, 5 ... Beam splitter, 6 ... Optical fiber, 6a ... Incoming / outgoing end face, 11 ... Optical communication system

Claims (10)

In an optical transceiver that is connected to an optical fiber and performs single-core bidirectional full-duplex optical fiber communication,
Light emitting means for emitting transmission light;
A light receiving means for receiving the received light;
Condensing means for condensing the transmitted light emitted from the light emitting means on the light incident / exit end face of the optical fiber, and condensing the received light emitted from the light incident / exit end face of the optical fiber on the light receiving means,
An optical path separating unit that guides the transmission light to the incident / exit end face of the optical fiber and guides the reception light to the light receiving unit;
Return light reflecting means for making the position of the focal point of the return light emitted from the light emitting means and reflected by the incident / exit end face of the optical fiber different from the focus position of the received light emitted from the incident / exit end face of the optical fiber; With
An optical transmission / reception apparatus, wherein the light receiving means is arranged at a position deviated from a focus of the return light and within a light receiving range of the received light. The return light reflecting means is configured such that the position of the incident / exit end face of the optical fiber is shifted along the optical axis with respect to the position of the focal point of the transmission light emitted from the light emitting means. The optical transceiver according to claim 1. The center of the return light emitted from the light emitting means and reflected by the incident / exit end face of the optical fiber is shifted from the center of the received light emitted from the incident / exit end face of the optical fiber. The optical transmission / reception apparatus according to claim 1, wherein the center of the reception light and the center of the return light collected by the light condensing means are separated. The optical axis of the return light emitted from the light emitting means and reflected by the incident / exit end face of the optical fiber is tilted with respect to the optical axis of the received light emitted from the incident / exit end face of the optical fiber. The optical transceiver according to claim 1. The return light reflected from the input / output end face of the optical fiber is tilted with respect to the optical axis of the optical fiber by tilting the optical axis of the transmission light emitted from the light emitting means and incident on the input / output end face of the optical fiber. The optical transmission / reception apparatus according to claim 4, wherein the optical axis is inclined with respect to the optical axis of the reception light emitted from the incident / exit end face of the optical fiber. In an optical communication system in which optical transmission / reception devices are connected by an optical fiber and single-core bidirectional full-duplex optical fiber communication is performed,
The optical transceiver is
Light emitting means for emitting transmission light;
A light receiving means for receiving the received light;
Condensing means for condensing the transmitted light emitted from the light emitting means on the light incident / exit end face of the optical fiber, and condensing the received light emitted from the light incident / exit end face of the optical fiber on the light receiving means,
An optical path separating unit that guides the transmission light to the incident / exit end face of the optical fiber and guides the reception light to the light receiving unit;
Return light reflecting means for making the position of the focal point of the return light emitted from the light emitting means and reflected by the incident / exit end face of the optical fiber different from the focus position of the received light emitted from the incident / exit end face of the optical fiber; With
An optical communication system, wherein the light receiving means is disposed at a position deviated from a focus of the return light and within a light receiving range of the received light. The return light reflecting means is configured such that the position of the incident / exit end face of the optical fiber is shifted along the optical axis with respect to the position of the focal point of the transmission light emitted from the light emitting means. The optical communication system according to claim 6. The center of the return light emitted from the light emitting means and reflected by the incident / exit end face of the optical fiber is shifted from the center of the received light emitted from the incident / exit end face of the optical fiber. The optical communication system according to claim 6, wherein the center of the received light and the center of the return light collected by the light collecting unit are separated. The optical axis of the return light emitted from the light emitting means and reflected by the incident / exit end face of the optical fiber is tilted with respect to the optical axis of the received light emitted from the incident / exit end face of the optical fiber. The optical communication system according to claim 6. The return light reflected from the input / output end face of the optical fiber is tilted with respect to the optical axis of the optical fiber by tilting the optical axis of the transmission light emitted from the light emitting means and incident on the input / output end face of the optical fiber. The optical communication system according to claim 9, wherein an optical axis is inclined with respect to an optical axis of received light emitted from an incident / exit end face of the optical fiber.

Images