JP2005062505A - Bidirectional optical module, device for performing bidirectional optical communication therewith, and bidirectional optical transmission system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical module capable of suppressing deterioration of receiving characteristics caused by propagation as a clad mode with a part of an optical signal outputted from a light emitting element of a local station and by its incidence to a light receiving part of the local station. <P>SOLUTION: The module is equipped with a first photonic crystal optical waveguide to be coupled with a transmission line from the communicating opposite side (a waveguide surrounded by or with the boundary defined by photonic crystals) 3, a light emitting element 7, a light receiving element 6, a wavelength division multiplex element 5 arranged in the manner that a transmitting optical signal from the light emitting element is passed and made incident to the first photonic crystal optical waveguide and that an input optical signal from a first optical fiber is reflected and made incident to the light receiving element, and a second photonic crystal optical waveguide 1 for providing a waveguide between the wavelength division multiplex element and the light emitting element. The photonic crystal materials 2, 4 for forming the first and second photonic crystal optical waveguides are composed of such photonic crystals that set, as a forbidden band, the frequency band of the optical signal to use. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention converts an electrical signal input to a single-fiber bidirectional optical communication system that realizes bidirectional optical communication with a single-fiber optical fiber, outputs the optical signal to the optical fiber, and inputs from the optical fiber. The present invention relates to a single-core bidirectional optical module that converts an optical signal to be converted into an electrical signal and outputs the electrical signal.

In recent years, with the arrival of a broadband network society, higher speed and higher capacity of communication are required. One of the systems that can meet these requirements is an optical communication system. Among the components of the optical communication system, the key device is an optical module, and various types have been proposed so far. I came.
For example, a conventional single-core bidirectional optical module and its operation are conceptually shown in FIG. 16 (see Patent Documents 1 and 2 below). In FIG. 16, the first optical fiber 61 + 62 obtained by obliquely cutting the optical fiber (hereinafter, the optical fiber consisting of the core x and the cladding y is expressed as “optical fiber x + y”) and the second optical fiber. A wavelength selection filter 5 that passes the optical signal from the first optical fiber 61 + 62 and reflects the optical signal from the second optical fiber 63 + 64 is disposed between the optical fiber 63 + 64 and the optical fiber 63 + 64. The optical module further includes a light emitting element 7, a lens 67 for condensing an optical signal output from the light emitting element 7, and a light receiving element 6 that receives an optical signal from the second optical fiber 63 + 64 reflected by the wavelength selection filter 5. Become. The above elements are fixed by various indicating members such as a ferrule and a split sleeve and an adhesive in a state where they are positioned so as to be optically efficiently coupled to each other.

The light emitting element 7 emits an optical signal in accordance with the input electric signal. This optical signal is collected by the lens 67 and input to the core 61 of the first optical fiber 61 + 62, passes through the wavelength selection filter 5, and is output to the second optical fiber 63 + 64. On the other hand, the optical signal input from the core 63 of the second optical fiber 63 + 64 is reflected by the wavelength selection filter 5, input to the light receiving element 6, and converted into an electrical signal. As described above, the conventional optical module can convert an input optical signal into an electrical signal and output it, and can also convert an input electrical signal into an optical signal and output it. One-core bidirectional optical communication in which optical signals for transmission and reception are exchanged with an optical fiber can be realized.
Japanese Unexamined Patent Publication No. 2000-121867 (paragraph numbers 0037 to 0042, FIG. 4) JP 2001-208932 A (summary, FIG. 1)

However, in the conventional optical module, the optical signal output from the light emitting element 7 is not sufficiently condensed by the lens 67 and is also input to the cladding 62, propagates as a cladding mode, and is received as stray light by catadioptric refraction. There is a problem in that it is input to the element 6 and becomes interference light with respect to the received light. In this respect, as shown in FIG. 17, the same applies to an optical module of a type in which the output light of the light emitting element 7 is directly coupled to the optical fiber 61 + 62 without using the lens 67.
Therefore, an optical module that can prevent a part of the optical signal from the light emitting element from propagating as a cladding mode and entering the light receiving element of the local station is desired.
In addition, the optical module that can prevent a part of the optical signal from the light emitting element from propagating as a clad mode and entering the light receiving element of the local station is used. An apparatus capable of bidirectional optical communication is desired.

  In order to solve the above-described problem, a bidirectional optical module according to claim 1 is a light-emitting element that emits a transmission optical signal in response to an input electric signal, and a light-receiving element that converts the incident optical signal into an electric signal. , A first photonic crystal optical fiber serving as a port used in optical communication, and the transmission optical signal from the light emitting element is transmitted and incident on the first photonic crystal optical fiber, Optical multiplexing / demultiplexing means manufactured and arranged to reflect the received optical signal input from the photonic crystal optical fiber and enter the light receiving element, and between the optical multiplexing / demultiplexing means and the light emitting element A second photonic crystal optical fiber providing an optical path; and a substrate in which the first photonic crystal optical fiber, the optical multiplexing / demultiplexing means, and the second photonic crystal optical fiber are embedded. Obtain. With this configuration, since no propagation light can exist in the cladding of the photonic crystal optical fiber, the optical signal from the light emitting element does not propagate to the light receiving element of the local station, so that interference light is reduced and reception characteristics can be improved. .

  The bidirectional optical module according to claim 2 is a portion excluding a light emitting element that emits a transmission optical signal in response to an input electric signal, a light receiving element that converts an incident optical signal into an electric signal, and an optical waveguide portion Is a photonic crystal optical waveguide substrate provided with a first optical waveguide section and a second optical waveguide section by inserting a diagonal cut into the substrate made of photonic crystal including the optical waveguide portion, and inserted into the cut Then, the transmitted optical signal from the light emitting element is transmitted and incident on the first optical waveguide section, and the received optical signal input from the first optical waveguide section is reflected and incident on the light receiving element. And optical multiplexing / demultiplexing means configured as described above. With this configuration, since a transmission optical signal cannot exist in the photonic crystal portion, the optical signal from the light emitting element does not propagate to the light receiving element of the local station, so that interference light is reduced and reception characteristics can be improved.

  According to a third aspect of the present invention, in the bidirectional optical module according to the first aspect, the first photonic crystal optical fiber, the optical multiplexing / demultiplexing means, and the second photonic crystal optical fiber are embedded. The substrate is inserted into the substrate with the photonic crystal optical fiber embedded and bonded at least until it reaches the core of the photonic crystal optical fiber, and plate-like optical multiplexing / demultiplexing means is inserted obliquely into the notch. The light receiving element is directly bonded to the vicinity of the optical multiplexing / demultiplexing means of the substrate. Thereby, the same effect as that of claim 1 can be obtained.

  According to a fourth aspect of the present invention, in the bidirectional optical module according to the first aspect, the first photonic crystal optical fiber, the optical multiplexing / demultiplexing means, and the second photonic crystal optical fiber are embedded. In the substrate, an oblique cut is made in the substrate embedded with the photonic crystal optical fiber until at least the core of the photonic crystal optical fiber is reached, and plate-like optical multiplexing / demultiplexing means is inserted obliquely into the cut. After the light receiving element is directly bonded to the electric circuit substrate, the light receiving element is bonded to the vicinity of the optical multiplexing / demultiplexing means of the substrate. This configuration enables active alignment that determines the mounting position of the light receiving element while monitoring the output signal of the light receiving element, reduces interference light, has excellent reception characteristics, and is a low-cost single-core bidirectional optical module. Can be realized.

  According to a fifth aspect of the present invention, in the bidirectional optical module according to the second aspect, the light receiving element is directly bonded to the vicinity of the optical multiplexing / demultiplexing means of the photonic crystal optical waveguide substrate. Thereby, the same effect as that of claim 2 can be obtained.

  According to a sixth aspect of the present invention, in the bidirectional optical module according to the second aspect, after the light receiving element is directly bonded to an electric circuit substrate, the optical multiplexing / demultiplexing unit of the photonic crystal optical waveguide substrate The light receiving element is bonded to the vicinity. This configuration enables active alignment that determines the mounting position of the light receiving element while monitoring the output signal of the light receiving element, reduces interference light, has excellent reception characteristics, and is a low-cost single-core bidirectional optical module. Can be realized.

  The invention according to claim 7 is the bidirectional optical module according to claim 3, 4 or 6, wherein the refractive index of the adhesive used for the bonding is the photonic crystal optical fiber or the photonic crystal optical waveguide substrate. Is approximately equal to the refractive index. With this configuration, it is possible to obtain an optical module for a single-core bi-directional optical communication system that has less refraction and irregular reflection between the photonic crystal optical fiber and the adhesive and has excellent reception characteristics.

  According to an eighth aspect of the present invention, in the bidirectional optical module according to the second, fifth, or sixth aspect, the substrate is made of any one of quartz-based glass, silicon crystal, and polymer. With this configuration, quartz-based glass, silicon crystal, or polymer is transparent to the wavelength band of signal light used for optical communications, so there is little refraction or irregular reflection between the photonic crystal optical fiber and the substrate. It is possible to provide an optical module for a single-core bidirectional optical communication system having excellent reception characteristics.

  According to a ninth aspect of the present invention, in the bidirectional optical module according to any one of the first to eighth aspects, a wavelength division multiplexing element is used as the optical multiplexing / demultiplexing means. With this configuration, the same effect as in the first or second aspect can be obtained.

  According to a tenth aspect of the present invention, in the bidirectional optical module according to any one of the first to eighth aspects, a half mirror is used as the optical multiplexing / demultiplexing means. With this configuration, the same effect as in the first or second aspect can be obtained.

  The invention according to claim 11 is the bidirectional optical module according to any one of claims 1 to 10, wherein the forbidden band of the photonic crystal includes a transmission wavelength of a transmission optical signal and a reception wavelength of a reception optical signal. Is substantially included. With this configuration, since a transmission optical signal cannot exist in the photonic crystal portion, the optical signal from the light emitting element does not propagate to the light receiving element of the local station, so that interference light is reduced and reception characteristics can be improved.

  An apparatus according to claim 12 is a bidirectional optical module according to any one of claims 1 to 11, and an electric signal to be transmitted is converted into a signal capable of driving the light emitting element included in the bidirectional optical module. A drive circuit for conversion; an amplifier circuit for amplifying an output signal of the light receiving element included in the bidirectional optical module; and an electric circuit for reproducing a data signal and a clock signal from the output signal of the amplifier circuit. Core bidirectional optical communication is possible.

  A thirteenth aspect of the present invention is the apparatus for performing bidirectional optical communication according to the twelfth aspect, wherein the apparatus is an optical transmission / reception apparatus. With this configuration, it is possible to obtain an optical transmission / reception device capable of single-core bidirectional optical communication.

  A fourteenth aspect of the invention includes the two optical transmission / reception apparatuses according to the thirteenth aspect, wherein the two optical transmission / reception apparatuses are connected to each other by a transmission optical fiber, and the optical signal and the second optical signal are connected. This is a single-core bidirectional optical transmission system using different wavelengths. With this configuration, it is possible to obtain a single-core bidirectional optical transmission system with a wavelength division multiplexing system that has less interference light and excellent reception characteristics.

  According to the present invention, since an optical waveguide surrounded by a photonic crystal having a forbidden band corresponding to a frequency used for transmission and reception is used as the optical waveguide, the photonic crystal portion cannot have propagating light of that frequency. Since the optical signal from the light emitting element does not propagate to the light receiving element of the local station, it is possible to obtain a single-core bidirectional optical module that can reduce the interference light and improve the reception characteristics.

  Further, according to an embodiment of the present invention, an apparatus capable of single-core bidirectional communication with excellent reception characteristics can be obtained by using an optical module in which the influence of crosstalk is reduced. This includes an optical transceiver and an optical transceiver module.

  In addition, according to another embodiment of the present invention, the optical transmission / reception apparatus of the present invention is provided on both the transmission side and the reception side, and by connecting with an optical fiber, single-core bidirectional communication can be performed with excellent reception characteristics. A possible optical transmission / reception system can be obtained.

Hereinafter, the present invention will be described in detail with reference to embodiments of the present invention and the accompanying drawings.
In addition, when showing the same element in several drawing, the same referential mark is attached | subjected.
FIG. 1 is a diagram conceptually showing an optical module of the present invention in order to explain the technical idea of the present invention. The optical module according to the present invention in FIG. 1 is the same as the optical module in FIG. 16 except for the following points. That is, according to the configuration of FIG. 1, instead of surrounding the waveguides 1 and 3 with a material having a refractive index different from that of the waveguides 1 and 3, the waveguides 1 and 3 are surrounded or covered with the photonic crystal materials 2 and 4, respectively. doing.

  Specifically, the photonic crystal material (for example, the clad of the photonic crystal optical fiber) 2 and 4 is provided with a periodic structure in which substances having different refractive indexes of optical wavelength sizes are periodically arranged. A nick band gap (PBG) can be formed. When the size of this PBG is expressed by Eg, light of the corresponding wavelength λ cannot enter the photonic crystal at Eg = hc / λ (h is Planck's constant, c is the speed of light). On the other hand, it becomes a photo insulator. Therefore, a periodic structure having a PBG corresponding to a wavelength used as an optical signal may be formed in the photonic crystal material (or cladding) 2 portion. Thereby, it is possible to prevent the optical signal from the light emitting element 7 from entering the light receiving element 6 through the waveguide covering portion (that is, the photonic crystal material) 2. Since the photonic crystal optical fiber has a structure in which holes are periodically arranged, it is also referred to as a microstructured optical fiber or a Holey optical fiber. The principle of the present invention can also be applied to an optical module of the type shown in FIG.

<First Embodiment>
FIG. 2 is a perspective view of the optical module according to the first embodiment of the present invention. 3 and 4 are cross-sectional views when the optical module of FIG. 2 is cut along planes Pa and Pb, respectively. 2 to 4, in the optical module 30 according to the first embodiment of the present invention, a chip carrier 9 to which a light emitting element 7 is bonded, photonic crystal optical fibers 1 + 2, 3 + 4, and a wavelength division multiplexing element 5 are embedded. And a light receiving element 6 flip-chip bonded to the glass substrate 10. A groove for embedding the photonic crystal optical fibers 1 + 2, 3 + 4 is cut in the glass substrate 10 in advance, and the photonic crystal optical fibers 1 + 2, 3 + 4 are embedded in the grooves and fixed with an adhesive 11. Here, instead of the glass substrate 10, a silicon crystal substrate or a polymer substrate transparent to the wavelength of the optical signal used for optical communication may be used. Grooves for inserting wavelength division multiplexing (WDM) elements 5 for multiplexing / separating optical signals are bonded to the glass substrate 10 after the photonic crystal optical fibers 1 + 2, 3 + 4 are bonded, respectively. The wavelength division multiplexing element 5 is inserted and bonded. The light receiving element 6 is provided with solder bumps 8, and is soldered to the glass substrate 10 using the solder bumps 8. At this time, the mounting position of the light receiving element 6 is accurately bonded to the position where the marker is attached. The refractive index of the adhesive 11 is desirably equal to that of the photonic crystal optical fibers 1 + 2, 3 + 4.

  Note that the PBG size Eg of the claddings 2 and 4 of the photonic crystal optical fibers 1 + 2 and 3 + 4 is determined according to, for example, the average of the wavelength λ1 used for transmission and the wavelength λ2 used for reception. In other words, the forbidden bands of the photonic crystals of the clads 2 and 4 are designed to include the wavelengths λ1 and λ2 for transmission and reception.

  The operation of the optical module 30 configured as described above will be described. First, an electrical signal input to the light emitting element 7 is converted into an optical signal and is incident on the core 1 and the cladding 2 of the photonic crystal optical fiber 1 + 2. Here, since the optical signal incident on the clad 2 is set to be a forbidden band of the photonic crystal optical fiber, it is attenuated by the periodic structure of the clad 2 and inputted to the core 1 of the photonic crystal optical fiber. Only the optical signal is propagated. The propagated optical signal input to the core 1 passes through the wavelength division multiplexing element 5 and is output. On the other hand, the optical signal input from the core 3 is reflected by the wavelength division multiplexing element 5, enters the light receiving element 6, is converted into an electric signal, and is output.

  As described above, according to the optical module 30 of the first embodiment of the present invention, by providing the photonic crystal optical fiber, it is possible to suppress the clad mode propagating in the clad of the optical fiber. Since the optical signal does not interfere with the received optical signal, good reception characteristics can be obtained.

<Second Embodiment>
FIG. 5 is a perspective view of an optical module according to the second embodiment of the present invention. 6 and 7 are cross-sectional views when the optical module of FIG. 5 is cut along planes Pa and Pb, respectively. 5 to 7, the optical module 30a according to the second embodiment of the present invention is formed on the glass substrate 10 after the light receiving element 6a is bonded to the electric circuit substrate 22 as compared with the first embodiment. Bonding with the adhesive 20 differs from the first embodiment in configuration. Since the optical signal is input from the back surface, the light receiving element 6a may be one in which the back surface is partially removed by etching in order to increase the light receiving efficiency. Further, instead of the glass substrate 10, a silicon crystal substrate or a polymer substrate transparent to the wavelength of the optical signal used for optical communication may be used. An electrical connector 24 is connected to the electrical circuit board 22 by electrical wiring 23. The electrical wiring 23 may be a flexible substrate having a high degree of mechanical freedom. Since the light receiving element 6a can monitor the output electric signal via the electric connector 24 while inputting the optical signal to the core 3 of the photonic crystal optical fiber when bonding to the glass substrate 10, the output electric signal The position can be determined so that becomes an appropriate value. The refractive index of the adhesive 20 is desirably equal to the refractive index of the claddings 2 and 4 of the photonic crystal optical fiber to be used.

The operation of the optical module 30a configured as described above will be described with reference to FIG.
First, an electrical signal input to the light emitting element 7 is converted into an optical signal, and this optical signal enters the core 1 and the cladding 2 of the photonic crystal optical fiber. Here, since the optical signal incident on the clad 2 is set to be a forbidden band of the photonic crystal optical fiber 1 + 2, it is attenuated by the periodic structure of the clad 2 and enters the core 1 of the photonic crystal optical fiber. Only the optical signal is propagated. The optical signal that has entered the core 1 and propagated passes through the wavelength division multiplexing element 5 and is output. On the other hand, the optical signal input from the core 3 is reflected by the wavelength division multiplexing element 5, enters the light receiving element 6a, is converted into an electric signal, and is output.

  As described above, according to the optical module of the second embodiment of the present invention, by providing the photonic crystal optical fiber, it is possible to suppress the clad mode propagating in the clad of the optical fiber and Since the signal does not interfere with the received optical signal, good reception characteristics can be obtained. Furthermore, since the positioning of the light receiving element can be performed while monitoring the output signal (active alignment), it can be simplified and the cost can be reduced.

<Third Embodiment>
FIG. 8 is a perspective view showing an optical module according to the third embodiment of the present invention. 9 and 10 are cross-sectional views when the optical module 30b of FIG. 8 is cut along the planes Pa and Pb, respectively. The optical module 30b in FIGS. 8 to 10 is the same as the optical fiber 30 in FIGS. 2 to 4 except for the following points. That is, in FIGS. 8 to 10, the glass substrate 10 is replaced with the photonic crystal substrate 26, the adhesive 11 and the optical fiber 1 + 2 are replaced with the waveguide 27, and the adhesive 11 and the optical fiber 3 + 4 are replaced with the waveguide 28. It is. A groove for inserting the wavelength division multiplexing element 5 is formed in the photonic crystal substrate 26 on which the waveguides 27 and 28 are formed, and the wavelength division multiplexing element 5 is inserted and bonded to the groove, whereby the waveguides 27 and 28 and An optical system comprising the wavelength division multiplexing element 5 sandwiched between the two is formed. Note that the refractive index of the adhesive used for bonding is preferably equal to the refractive index of the photonic crystal substrate 26. The PBG size Eg of the photonic crystal substrate 26 is determined according to, for example, the average of the wavelength λ1 used for transmission and the wavelength λ2 used for reception. In other words, the forbidden band of the photonic crystal on the photonic crystal substrate 26 is designed to include the wavelengths λ1 and λ2 for transmission and reception.

  The operation of the optical module 30b configured as described above will be described with reference to FIG. First, an electric signal input to the light emitting element 7 is converted into an optical signal and input to a photonic crystal optical waveguide 27 (which means a waveguide surrounded by a photonic crystal material (a boundary is defined)). The Here, since the optical signal input to the photonic crystal waveguide 27 is set so as to be a forbidden band of the photonic crystal substrate 26, it is attenuated by the periodic structure of the photonic crystal substrate 26, and the photonic crystal waveguide Only the optical signal input to the waveguide 27 is propagated. The propagated optical signal passes through the wavelength division multiplexing element 5 and is output. On the other hand, the optical signal input from the photonic crystal waveguide 28 is reflected by the wavelength division multiplexing element 5, is incident on the light receiving element 6, is converted into an electric signal, and is output.

  As described above, according to the optical module of the third embodiment of the present invention, by providing the photonic crystal waveguide, it is possible to suppress a mode propagating other than the waveguide and to receive the optical signal of the local station. Since the optical signal is not disturbed, good reception characteristics can be obtained.

<Fourth embodiment>
FIG. 11 is a perspective view showing an optical module according to the fourth embodiment of the present invention. 12 and 13 are cross-sectional views when the optical module 30c of FIG. 11 is cut along planes Pa and Pb, respectively. The optical module 30c of FIGS. 11-13 replaces the components 1-5, 10 of the optical module 30a of FIGS. 5-7 with the components 26-28, 5 of FIGS.

  Therefore, according to the optical module 30c of the fourth embodiment of the present invention, by providing the photonic crystal waveguide, it is possible to suppress a mode that propagates other than the waveguide, and the optical signal of the local station is received. Since the optical signal is not disturbed, good reception characteristics can be obtained. Further, since the positioning of the light receiving element can be performed while monitoring the output signal, it can be simplified and the cost can be reduced.

<Fifth embodiment>
FIG. 14 shows a single-core bidirectional light using bidirectional optical modules 30, 30a, 30b or 30c (hereinafter collectively referred to as “optical module 30”) according to the first to fourth embodiments of the present invention. It is a schematic block diagram which shows the optical transmission / reception circuit or optical transmission / reception module of the apparatus which communicates. In FIG. 14, an optical transmission / reception circuit 38 includes the above-described optical module 30, an amplification circuit 35 that amplifies a reception signal from the light receiving element 6 or 6a of the optical module 30, and a clock recovery circuit that extracts a clock component from the reception signal. 36, a data reproducing circuit 37 for reproducing a data signal from the received signal and the clock signal, and a driving circuit 34 for driving the light emitting element 7 included in the optical module. The optical transmission / reception circuit 38 is optically coupled to the transmission optical fiber 32.

The operation of the optical transmission / reception circuit 38 configured as described above will be described.
The optical signal transmitted through the transmission optical fiber 32 is input to the optical module 30 of the optical transmission / reception circuit 38. The optical signal input to the optical module 30 is reflected by the wavelength division multiplexing element 5, enters the light receiving element 6 or 6 a, is converted into an electric signal, and is output to the amplifier circuit 35. The electric signal amplified by the amplifier circuit 35 is branched into two, one being input to the clock recovery circuit 36 and the other being input to the data recovery circuit 37. The clock recovery circuit 36 generates a clock signal from the input electric signal and supplies it to the data recovery circuit 37 and other circuit portions. The data reproduction circuit 37 reproduces a data signal by performing waveform shaping on the input electrical signal using the clock signal input from the clock recovery circuit 36. Further, a signal (data) to be transmitted in the optical transmission / reception circuit 38 is input to the light emitting element 7 of the optical module 30 through the driving circuit 34 and converted into an optical signal, transmitted through the wavelength division multiplexing element 5, and an optical fiber for transmission. 32.

  Thus, according to the apparatus of the fifth embodiment of the present invention, a good data signal and clock signal can be obtained without the optical signal of the local station interfering with the received optical signal. The fifth embodiment of the present invention can be applied to an independent apparatus or an optical transmission / reception module constituting a part of the system as long as it performs single-core bidirectional optical communication. it can.

<Sixth Embodiment>
FIG. 15 is a schematic block diagram of an optical transmission system according to the sixth embodiment of the present invention. The optical transmission system of FIG. 15 is configured by connecting two devices 39 and 40 that perform optical transmission and reception through a transmission optical fiber 32. The two devices 39 and 40 each include the optical transmission / reception circuit (or optical module 30) 38 of FIG. 14 in order to perform single-core bidirectional optical communication. In each of the optical transmission / reception circuits 38 of the two devices 39 and 40, the light receiving element and the wavelength division multiplexing element are selected so that the other can receive the wavelength of the optical signal output by one so that communication can be established. . Each optical transmission / reception circuit 38 preferably uses different frequencies for transmission / reception.

For example, if the optical transmission / reception circuit 38 of the device 39 transmits 1.3 μm band light and receives 1.5 μm band light, the optical transmission / reception circuit 38 of the device 40 transmits 1.5 μm band light. The reverse frequency band is used for transmission and reception, such as receiving light in the 1.3 μm band. In this way, the optical signal of the local station interferes with the received signal by connecting the two optical transceivers 38 having different wavelengths of the optical signal to be transmitted and the optical signal to be received by the transmission optical fiber 32 to face each other. Therefore, it is possible to perform good single-core bidirectional optical communication.
In the embodiment described above, the wavelength division multiplexing element is used, but a half mirror may be used instead.

  According to the present invention, since an optical waveguide surrounded by a photonic crystal having a forbidden band corresponding to a frequency used for transmission and reception is used as the optical waveguide, the photonic crystal portion cannot have propagating light of that frequency. Since the optical signal from the light emitting element does not propagate to the light receiving element of the local station, it is possible to obtain a single-core bidirectional optical module with less interference light and improved reception characteristics. Therefore, the present invention uses a single-core optical fiber. It can be used for a bidirectional communication system.

The figure which represented the optical module of this invention notionally The perspective view of the optical module by the 1st Embodiment of this invention Sectional drawing along plane Pa of the optical module of FIG. Sectional drawing along plane Pb of the optical module of FIG. The perspective view of the optical module by the 2nd Embodiment of this invention Sectional drawing along plane Pa of the optical module of FIG. Sectional drawing along plane Pb of the optical module of FIG. The perspective view of the optical module by the 3rd Embodiment of this invention Sectional drawing along plane Pa of the optical module of FIG. Sectional drawing along plane Pb of the optical module of FIG. The perspective view of the optical module by the 4th Embodiment of this invention Sectional drawing along plane Pa of the optical module of FIG. Sectional drawing along plane Pb of the optical module of FIG. Schematic block diagram showing an apparatus for performing optical transmission and reception according to a fifth embodiment of the present invention. Schematic block diagram showing an optical transmission system according to a sixth embodiment of the present invention. Conceptual diagram of a conventional optical module Conceptual diagram of another conventional optical module

Explanation of symbols

1, 3 Photonic crystal optical fiber core (waveguide)
2, 4 Clad of photonic crystal optical fiber (photonic crystal material)
5 Wavelength division multiplexing elements (wavelength selection filters, WDM elements)
6, 6a Light-receiving element 7 Light-emitting element 8 Solder bump 9 Chip carrier 10 Glass substrate 11, 20 Adhesive 22 Substrate for electric circuit 23 Electric wiring 24 Electric connector 26 Photonic crystal substrate 27, 28 Photonic crystal waveguide (waveguide)
30, 30a to 30c Optical module 32 Transmission optical fiber 34 Drive circuit 35 Amplifier circuit 36 Clock recovery circuit 37 Data recovery circuit 38 Optical transmission / reception circuit 39, 40 Apparatus (apparatus) for optical transmission / reception
61 Core of the first optical fiber 62 Cladding of the first optical fiber 63 Core of the second optical fiber 64 Cladding of the second optical fiber

Claims (14)

  A light emitting element that emits a transmission optical signal in response to an input electric signal, a light receiving element that converts an incident optical signal into an electric signal, and a first photonic crystal optical fiber that serves as a port used for optical communication; The transmission light signal from the light emitting element is transmitted and incident on the first photonic crystal optical fiber, and the reception light signal input from the first photonic crystal optical fiber is reflected to reflect the light receiving element. Optical multiplexing / demultiplexing means manufactured and arranged so as to be incident on the light, a second photonic crystal optical fiber that provides an optical path between the optical multiplexing / demultiplexing means and the light emitting element, and the first photonic A bidirectional optical module comprising: a crystal optical fiber; the optical multiplexing / demultiplexing means; and a substrate in which the second photonic crystal optical fiber is embedded.   A light emitting element that emits a transmission optical signal in response to an input electric signal, a light receiving element that converts an incident optical signal into an electric signal, and a portion other than the optical waveguide portion are formed by oblique cuts in a substrate made of a photonic crystal By including the optical waveguide portion, the photonic crystal optical waveguide substrate provided with the first optical waveguide portion and the second optical waveguide portion, and the optical signal transmitted from the light emitting element inserted into the notch are Optical multiplexing / demultiplexing means configured to transmit and enter the first optical waveguide unit, reflect a received optical signal input from the first optical waveguide unit, and enter the light receiving element; Bidirectional optical module equipped.   The substrate in which the first photonic crystal optical fiber, the optical multiplexing / demultiplexing means, and the second photonic crystal optical fiber are embedded has at least an oblique cut in the substrate in which the photonic crystal optical fiber is embedded and bonded. It is inserted until it reaches the core of the photonic crystal optical fiber, and a plate-like optical multiplexing / demultiplexing means is obliquely inserted into the cut, and the light receiving element is provided in the vicinity of the optical multiplexing / demultiplexing means of the substrate The bidirectional optical module according to claim 1, which is directly bonded.   The substrate in which the first photonic crystal optical fiber, the optical multiplexing / demultiplexing means, and the second photonic crystal optical fiber are embedded has at least an oblique cut in the substrate in which the photonic crystal optical fiber is embedded. The photonic crystal optical fiber is inserted until it reaches the core, and a plate-like optical multiplexing / demultiplexing means is inserted obliquely into the cut, and after the light receiving element is directly bonded to the electric circuit substrate, the light receiving element 2. The bidirectional optical module according to claim 1, wherein a substrate is adhered to a portion of the substrate in the vicinity of the optical multiplexing / demultiplexing means.   3. The bidirectional optical module according to claim 2, wherein the light receiving element is directly bonded to a portion of the photonic crystal optical waveguide substrate in the vicinity of the optical multiplexing / demultiplexing means.   3. The bidirectional optical module according to claim 2, wherein the light receiving element is directly bonded to an electric circuit substrate, and then the light receiving element is bonded to a portion of the photonic crystal optical waveguide substrate in the vicinity of the optical multiplexing / demultiplexing means.   The bidirectional optical module according to claim 3, 4 or 6, wherein a refractive index of an adhesive used for the bonding is substantially equal to a refractive index of the photonic crystal optical fiber or the photonic crystal optical waveguide substrate.   7. The bidirectional optical module according to claim 2, 5 or 6, wherein the substrate is made of any one of quartz glass, silicon crystal, and polymer.   The bidirectional optical module according to any one of claims 1 to 8, wherein a wavelength division multiplexing element is used as the optical multiplexing / demultiplexing means.   The bidirectional optical module according to claim 1, wherein a half mirror is used as the optical multiplexing / demultiplexing means.   The bidirectional optical module according to any one of claims 1 to 10, wherein the forbidden band of the photonic crystal substantially includes a transmission wavelength of a transmission optical signal and a reception wavelength of a reception optical signal.   The bidirectional optical module according to any one of claims 1 to 11, a drive circuit that converts an electric signal to be transmitted into a signal capable of driving the light emitting element included in the bidirectional optical module, and the bidirectional An apparatus for performing single-core bidirectional optical communication, comprising: an amplifier circuit that amplifies an output signal of the light receiving element included in an optical module; and an electric circuit that regenerates a data signal and a clock signal from the output signal of the amplifier circuit.   The apparatus for performing bidirectional optical communication according to claim 12, wherein the apparatus is an optical transceiver. 14. Two optical transmission / reception devices according to claim 13, wherein the two optical transmission / reception devices are connected to each other by a transmission optical fiber, and both optical fibers and the second optical signal use different wavelengths. Muco-optical transmission system.

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