JP2001004878A - Optical transmission/reception module and optical cable and single core two-way optical communication system by using them - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical transmission/reception module capable of preventing extreme reduction of reception efficiency. SOLUTION: An optical transmission/reception module 10 for executing two- way communication by a single core optical fiber 14 has a receptacle 11 from which a plug 13 of an optical cable having a short optical fiber length cannot be detached, a first light emitting element for emitting linear polarized-light as transmission signal light, a light receiving element for receiving reception signal light, and a polarized-light branching element for bisecting reception signal light into orthogonal polarized-light components. Transmission signal light from the first light emitting element is not branched by the polarized-light branching element but passes through, and thereafter optical coupling with the optical fiber 14 is executed, and reception signal light from the optical fiber 14 is branched by the polarized-light branching element and enters the light receiving element.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical transmission / reception module and an optical cable used in an optical communication system for transmitting and receiving by sharing one optical fiber, and a one-core bidirectional optical communication system using the same. . Especially I
The present invention relates to a digital communication system capable of high-speed transmission such as EEE1394 or USB2.

[0002]

2. Description of the Related Art As a conventional example of such an optical transmission / reception module, Japanese Patent Application Laid-Open No. Hei 10-153720 discloses a polarization splitting element as an optical splitting element, which is combined with a light source that emits linearly polarized light. Optical transmission / reception modules that reduce optical branch loss have been proposed.

FIG. 7 is a side sectional view of the optical transceiver module. 7, the optical cable 62 includes an optical plug 61 and an optical fiber (not shown) provided in the optical cable 62.

The optical transmitting / receiving module 50 has a receptacle section 5 for holding the position where the optical plug 61 is inserted.
7, a triangular prism 52 mounted on the semiconductor substrate 51, a submount 53 similarly mounted on the semiconductor substrate 51 and mounting a light emitting element 54, and a lens 56.

The transmission signal light 63 emitted from the light emitting element 54 is reflected by the polarization splitting film formed on the surface of the triangular prism 52 mounted on the semiconductor substrate 51 and the optical path is deflected by 90 degrees. Focused light plug 6
The light enters the optical fiber in the first optical cable 62, transmits the optical fiber, and enters the optical transmission / reception module.

On the other hand, the received signal light 6 emitted from the optical fiber
4 is condensed by a lens 56 and the triangular prism 52
Incident on. The polarization splitting film formed on the triangular prism 52 is designed to reflect S-polarized light and transmit P-polarized light, so that the polarization state changes from linear to random during transmission through the optical fiber. The signal light 64 passes through the polarization splitting film at half the energy, and enters the light receiving element 55 formed on the semiconductor substrate 51.

As a proposal example, the present inventor has disclosed in Japanese Patent Application No.
No. 0-8054, using a polarization splitting element as an optical splitting element and combining it with a light source that emits linearly polarized light, reduces the optical splitting loss on the transmission side, and reduces the reception signal light transmitted through an optical fiber by a depolarizer. We have proposed an optical transceiver module that is not affected by reception even if the polarization state is unstable.

FIG. 8 shows a configuration diagram of the optical transceiver module. 8, the light transmission module 80 includes a light emitting element 81 that emits linearly polarized light, a lens 82, a polarizing beam splitter 83, a depolarizer 84, a lens 85, a lens 86, and a light receiving element 87.

The transmission signal light 88 emitted from the light emitting element 81
Are transmitted through the lens 82 and converted into parallel rays, and then enter the polarization beam splitter 83. Since the polarization beam splitter 83 transmits S-polarized light, the transmission signal light 88 passes through the polarization beam splitter 83 without energy loss and enters the depolarizer 84. The depolarizer 8
The transmission signal light 88 incident on 4 is changed from linearly polarized light to random polarized light, condensed by a lens 85 and incident on an optical fiber 90, transmitted through the optical fiber 90, and then incident on a partner optical transmission / reception module.

On the other hand, the received signal light 89 emitted from the optical fiber 90 is converted into parallel rays by a lens 85, then enters a depolarizer 84, is randomly polarized irrespective of the incident polarization state, and is subjected to a polarization beam splitter 83. Incident on. Since the polarization beam splitter 83 is designed to transmit S-polarized light and reflect P-polarized light, half of the energy of the received signal light 89 is reflected by the polarization beam splitter 83 and enters the light receiving element 87.

FIG. 9 is a configuration diagram of a depolarizer used in the optical transceiver module shown in FIG. The depolarizer attaches a (2n-1) / 2λ plate to a transparent plate having the same refractive index as that of the (2n-1) / 2λ plate, and places the bonded surface on the optical axis of the optical fiber. It is formed by rotating the optical axis by 45 degrees with respect to the optical axis of the polarization splitter.

FIG. 10 is a configuration diagram of another depolarizer used in the optical transceiver module shown in FIG. The depolarizer is formed by bonding a 90-degree optical rotation plate (optical rotation material) and a transparent plate (light transmission material) having the same refractive index as that of the optical rotation plate, and placing the bonding surface on the optical axis of the optical fiber. .

The depolarizer shown in FIGS. 9 and 10 functions to equally divide the light intensity between two orthogonal polarization components into two.

[0014]

However, the prior art has the following problems.

1) The received signal light 64 transmitted through the optical fiber does not become randomly polarized light, for example, when the fiber length is as short as 1 m, so that there is a problem that the receiving efficiency is extremely reduced.

2) The light emitting device 54 composed of a semiconductor laser device has a problem that the power consumption is large and the life is short.

3) Since the polarization state of the received signal light 64 changes due to the vibration of the optical fiber, etc., the intensity of the received signal light 64 changes according to the vibration of the optical fiber. Therefore,
There is a problem that the S / N is reduced.

4) Since the triangular prism 52 is processed in a separate process, and a polarization splitting film is formed thereon by a dielectric multilayer film, it is very expensive.

5) When the triangular prism 52 is installed on the semiconductor substrate 51, position adjustment is required, which hinders cost reduction.

6) The optical fiber is made of POF (Plastic Optica).
The used wavelength and NA (Numerical Aperture) are different between l Fiber) and PCF (Polymer Clad Fiber), and either one of the optical fibers cannot be used.

The following problem occurs in the proposed example.

1) The depolarizer 84 is complicated and the material is expensive.

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide an optical transmission / reception module and an optical cable which do not significantly reduce reception efficiency, and a single-core bidirectional optical communication system using them.

[0024]

In order to achieve the above object, an optical transceiver module according to a first aspect of the present invention is an optical transceiver module for performing bidirectional communication using a single optical fiber. The optical cable has a short plug which cannot be detached, a first light emitting element that emits linearly polarized light as transmission signal light, a light receiving element that receives reception signal light, and a polarization component that orthogonalizes the reception signal light into two components. And a transmission signal light from the first light emitting element passes through the polarization splitting element without branching, and is then optically coupled to the optical fiber to receive a signal from the optical fiber. Light is split by the polarization splitting element and is incident on the light receiving element.

An optical transceiver module according to a second aspect of the present invention is an optical transceiver module for performing bidirectional communication using a single-core optical fiber, wherein the optical fiber has a short optical fiber and a plug in which an optical cable cannot be detached. A first light-emitting element that emits linearly polarized light as transmission signal light, a second light-emitting element that emits transmission signal light, a light-receiving element that receives reception signal light, and two polarization components orthogonal to the reception signal light. Having a polarization splitting element for splitting, the transmission signal light from the light emitting element, after passing without branching in the polarization splitting element, optically coupled to the optical fiber, the reception signal light from the optical fiber, The light is split by the polarization splitting element and is incident on the light receiving element.

Further, an optical transceiver module according to a third aspect of the present invention is an optical transceiver module for performing bidirectional communication by using a single-core optical fiber, comprising: A first light emitting element that emits linearly polarized light as the transmission signal light, a light receiving element that receives the reception signal light, a polarization splitting element that divides the reception signal light into two orthogonal polarization components, and a depolarizer,
The transmission signal light from the first light emitting element passes through the polarization splitting element without branching, and after passing through the depolarizer, is optically coupled to the optical fiber, and the reception signal light from the optical fiber is After passing through the depolarizer, the light is split by the polarization splitter and is incident on the light receiving element.

Further, an optical transceiver module according to a fourth aspect of the present invention is an optical transceiver module for performing bidirectional communication by using a single-core optical fiber, wherein the optical cable has a short optical fiber length and a pluggable / removable plug. A first light-emitting element that emits linearly polarized light as transmission signal light, a second light-emitting element that emits transmission signal light, a light-receiving element that receives reception signal light, and two polarization components orthogonal to the reception signal light. Having a polarization splitting element and a depolarizer, the transmission signal light from the light emitting element passes without splitting in the polarization splitting element, and after passing through the depolarizer, is optically coupled to the optical fiber; The signal light received from the optical fiber is
After passing through the depolarizer, the light is split by the polarization splitter and is incident on the light receiving element.

In addition, the optical transceiver module of the fifth invention of the present invention is the optical transceiver module of the second or fourth invention, wherein the first light emitting element is a semiconductor laser element and the second light emitting element is a semiconductor laser element. Element is SLD or L
When the transmission speed is 400 Mbps or more, optical communication is performed using the first light emitting element, and the transmission speed is 40 Mbps.
At less than 0 Mbps, optical communication is performed using the second light emitting element.

Further, in the optical transceiver module according to the sixth aspect of the present invention, in the optical transceiver module according to the second or fourth aspect, the first light emitting element is a light emitting element emitting light having a wavelength of 850 nm. And the second
Are light emitting elements that emit light having a wavelength of 650 nm, and when the transmission speed is 400 Mbps or more, the first
Optical communication is performed using the light emitting element of
At less than bps, optical communication is performed using the second light emitting element.

In the optical transceiver module according to the seventh aspect of the present invention, in the optical transceiver module according to the third or fourth aspect, the depolarizer is provided with a hole (2n- 1) A λ plate is formed by rotating an optical axis by 45 degrees with respect to the optical axis of the polarization splitter.

In addition, in the optical transceiver module according to the eighth aspect of the present invention, in the optical transceiver module according to the third or fourth aspect, the depolarizer may be configured such that a luminous flux area / 2 =
It is characterized by being formed by a 90-degree optical rotation plate having a hole that satisfies the sum of the hole areas.

In addition, the optical transceiver module according to the ninth aspect of the present invention is the optical transceiver module according to the seventh or eighth aspect, wherein the (2n-1) / 2λ plate or the 90-degree optical rotation plate has a high liquid crystal property. It is characterized by comprising a molecular film.

Further, the optical transceiver module according to the tenth aspect of the present invention is the optical transceiver module according to any one of the first to ninth aspects.
In the optical transmitting and receiving module according to another aspect of the invention, the polarization splitting element is formed by attaching a polarizing film to an inclined surface.

In addition, an optical transceiver module according to an eleventh aspect of the present invention is the optical transceiver module according to the tenth aspect, wherein the slope is formed of a mold resin.

In addition, an optical transmission / reception module according to a twelfth aspect of the present invention is the optical transmission / reception module according to any one of the first to eleventh aspects, wherein the optical fiber uses the excitation NA of the transmission optical system. The smallest N in
A or less.

In addition, the optical cable according to the thirteenth aspect of the present invention is made of POF or PCF having a sufficiently long fiber with a detachable plug attached to both ends of the receptacle of the optical transceiver module according to the first or second aspect. It is characterized by the following.

In addition, an optical cable according to a fourteenth aspect of the present invention is characterized in that the optical cable comprises a POF or a PCF having plugs attached to both ends of the optical transceiver module according to the third or fourth aspect of the present invention. Things.

In addition, a one-core bidirectional optical communication system according to a fifteenth aspect of the present invention includes the optical transceiver module according to any one of the first to fourteenth aspects, and the optical cable according to the thirteenth or fourteenth aspect. It is characterized by having.

According to the above configuration, since the receptacle of the optical cable having the short optical fiber length and the plug of which the plug is not detachable is used for the optical transceiver module, the shortest fiber length of the optical cable using the detachable plug can be set sufficiently long. PO
Since the received signal light transmitting F can be made sufficiently random polarized light, it is possible to prevent an optical cable having a short optical fiber length from being attached and detached, and to prevent the reception efficiency from being extremely lowered.

Also, since SLDs and LEDs are slower than semiconductor laser elements, using SLDs and LEDs instead of semiconductor laser elements during low-speed transmission can increase power consumption and extend the life of semiconductor laser elements. Can be.

Further, since the light that has passed through the depolarizer is randomly polarized, the reception efficiency is extremely reduced when the optical fiber length is short, and the polarization state of the received signal light changes due to the vibration of the optical fiber. It is possible to prevent the intensity of the received signal light from changing in accordance with the vibration of the optical fiber and reducing the S / N.

Furthermore, a polarizing film is less expensive than a polarizing branching film, which can promote a reduction in the cost of the system.

In addition, the liquid crystalline polymer film is inexpensive, and can promote the cost reduction of the system.

In addition, the wavelength of the transmission signal light is switched according to the optical fiber used, and the excitation NA of the transmission optical system is changed.
Is set to be equal to or smaller than the smallest NA of the optical fiber using the optical fiber. Therefore, any optical fiber can use a sufficiently wide band of the optical fiber and can communicate using both the POF and PCF optical fibers.

[0045]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 shows a first embodiment of the present invention.
FIGS. 7A and 7B are diagrams showing a state in which the optical transceiver module according to the embodiment of the present invention is plugged in, wherein FIG.
Is a side sectional view.

In the figure, an optical cable is composed of a plug handle 12 and a plug 1 attached to both ends of the optical cable.
3. It comprises an optical fiber 14 arranged at the center (center axis) of the optical cable.

The optical transmitting / receiving module 10 includes the plug 1
It comprises a receptacle 11 into which 3 is inserted to hold a position, a lens 15, an optical device 20, a drive integrated circuit 16, an amplifier integrated circuit 17, and external input / output terminals 18 and 19.

FIG. 2 shows the structure of the optical device 20.
In the figure, (a) is a plan view and (b) is a side sectional view.

In the figure, the optical device 20 includes an electrode 25
, A light-receiving element 22 mounted thereon, a monitoring light-receiving element 23 for monitoring the transmission signal light of the light-emitting element 27, a mold part 24 in which the light-receiving elements 22 and 23 are resin-sealed, It comprises a submount 26 with the light emitting element 27 mounted on a printed circuit board 21.

In FIGS. 1 and 2, the transmission signal light emitted from one end of the light emitting element 27 enters the mold section 24, is reflected by the slope 28 of the mold section 24, enters the monitor light receiving element 23, and emits light. The light quantity of the element 27 is monitored. This signal enters the drive integrated circuit 16 and is used to keep the light amount of the light emitting element 27 constant.

The transmission electric signal input from the external input / output terminal 19 is input to the driving integrated circuit 16 and the light emitting element 27
And is converted into transmission signal light.

The transmission signal light emitted from the other end of the light emitting element 27 is deflected by 90 degrees in the optical path without branching by the polarizing film 30 which is a polarization splitting element attached to the inclined surface 29 of the mold part 24, After being collected by the optical fiber 1, the light enters the optical fiber 14 inside the plug 13,
4 and is incident on the optical transmission / reception module.

The received signal light from the other optical transmission / reception module is emitted from the optical fiber 14 inside the plug 13, condensed by the lens 15, and split by the polarizing film 30 attached to the inclined surface 29 of the mold part 24 for two minutes. The transmitted light enters the light receiving element 22 and is converted into a received electric signal, and is amplified by the amplifier integrated circuit 17.
9 to an electronic circuit (not shown) outside the optical transceiver module.

The diameter of the plug 13 is, for example, φ4 mm
Then, the existing plug diameter is φ1.25, 2.5,
Since it is 3.5, an existing optical cable cannot be attached to the present optical transceiver module. Obviously, the receptacle 11 of the optical transceiver module 10
Is a hole diameter corresponding to φ4 mm.

Therefore, if the minimum length of the optical cable is sufficiently long, for example, 10 m, the received signal light transmitted through the optical fiber 14 is randomly polarized, so that it is possible to avoid a problem that the receiving efficiency is extremely reduced. .

The polarizing film 30 is the same as that used for the liquid crystal display element. A film formed by uniaxially stretching a polyvinyl alcohol (PVA) film is sandwiched between protective films, and an adhesive is applied to one surface. Formed. As an example of such a polarizing film,
There is Sumikaran manufactured by Sumitomo Chemical.

(Second Embodiment) FIG. 3 shows a second embodiment of the present invention.
FIGS. 7A and 7B are diagrams showing a state in which the optical transceiver module according to the embodiment of the present invention is plugged in, wherein FIG.
Is a side sectional view.

In FIG. 3, the optical cable includes a plug handle 12 and a plug 1 attached to both ends of the optical cable.
3. It comprises an optical fiber 14 arranged at the center (center axis) of the optical cable.

The optical transmitting / receiving module 10 includes the plug 1
3 is inserted and holds a position, a lens 15, an optical device 20, a drive integrated circuit 16, an amplifier integrated circuit 17, external input / output terminals 18, 19, and a depolarizer 3.
1

FIG. 4 shows the configuration of the optical device 20.
In the figure, (a) is a plan view and (b) is a side sectional view.

In the figure, the optical device 20 has an electrode 25
, A light receiving element 22 mounted thereon, a monitoring light receiving element 23 for monitoring the transmission signal light of the light emitting elements 27 and 32, and both of the light receiving elements 22 and 23
24, the printed circuit board 21
Sub-mount 26 with light-emitting elements 27 and 32 mounted on
Consists of

3 and 4, the transmission signal light emitted from one end of the light emitting element 27 or 32 is
4, the light is reflected by the slope 28 of the mold part 24, and is incident on the monitor light receiving element 23, where the light emitting element 27 or 3
2 is monitored. This signal enters the drive integrated circuit 16 and is used to keep the light intensity of the light emitting element 27 or 32 constant.

The transmission electric signal input from the external input / output terminal 19 is input to the driving integrated circuit 16 and the light emitting element 27
Or 32 is driven and converted into transmission signal light.

The transmission signal light emitted from the other end of the light emitting element 27 or 32 is deflected by 90 degrees in the optical path without splitting by the polarizing film 30 which is a polarizing splitting element attached to the inclined surface 29 of the mold section 24. After being transmitted through the depolarizer 31 to be randomly polarized and condensed by the lens 15, the light enters the optical fiber 14 inside the plug 13, is transmitted through the optical fiber 14, and is incident on the partner optical transmission / reception module.

The signal light received from the optical transmitter / receiver module is emitted from the optical fiber 14 inside the plug 13, collected by the lens 15, transmitted through the depolarizer 31, turned into random polarized light, and adhered to the inclined surface 29 of the mold 24. The transmitted light split into two is incident on the light receiving element 22 by the attached polarizing film 30 and is converted into a received electric signal. The amplified electric signal is amplified by the amplifier integrated circuit 17. Input to an electronic circuit (not shown).

The plug 13 is an existing plug. Here, an EIAJRC 5720 optical round connector having a diameter of 3.5 was used. This connector is used in a digital audio optical communication system, and the optical cable has a minimum length of 60c.
m. However, even when such a short optical cable is used, since the received signal light is randomly polarized by the depolarizer 31, it is possible to avoid a problem that the reception efficiency is extremely reduced. Further, even if the optical cable vibrates and the polarization state of the received signal light fluctuates, the depolarizer 3
Since the light passing through 1 becomes random polarized light, the problem that the S / N is reduced does not occur.

In the IEEE 1394 digital communication system, the transmission speed is set to 100 Mbps, 200 Mbps, 40 Mbps.
The optical transmission / reception module is divided into categories of 0 Mbps to provide backward compatibility with speed. For example, 100 Mbp
s and the 400 Mbps optical transceiver module communicate with each other, the 400 Mbps optical transceiver module is 100 Mbps.
Transmit at bps.

Therefore, the first light emitting element 27 is
(Super Luminescence Diode) or LED (Light Em
When the second light emitting element 32 is a semiconductor laser element, the second light emitting element 32 is driven at 400 Mbps or more, and the first light emitting element 27 is driven at less than 400 Mbps. This makes it possible to extend the life of the semiconductor laser element. This is not limited to the present embodiment, and the second embodiment can add a second light emitting element in the above-described first embodiment and perform drive control in the same manner as in the present embodiment, so that power consumption can be suppressed and the semiconductor laser can be controlled. It is possible to extend the life of the device.

In the IEEE 1394 digital communication system, the type of optical fiber is defined as PCF for 800 Mbps or more and POF for less than 800 Mbps. Table 1 shows the types and characteristics of the optical fibers.

[0071]

[Table 1] In the table, SI-POF is an abbreviation for Step Index-POF,
GI-POF is an abbreviation for GradedIndex-POF.

Therefore, the POF has a wavelength of 650 n.
m, the minimum NA is 0.3, the PCF is 850 nm, and the NA is 0.35.
Semiconductor laser element, the second light emitting element 32 is 650n
If the excitation NA of the semiconductor laser element, SLD or LED, and the optical system of m is 0.3, the first light emitting element 27 is driven at 800 Mbps or more, and the second light emitting element 32 is driven at less than 800 Mbps. In addition, it is possible to cope with a wide transmission speed with the same optical transceiver module regardless of the type of optical fiber. This is not limited to the present embodiment, but by adding a second light emitting element in the above-described first embodiment and performing drive control in the same manner as in the present embodiment, regardless of the type of optical fiber. The same optical transceiver module can support a wide transmission speed.

In the present embodiment, two light emitting elements 27,
Although 32 are arranged on the submount 26, it goes without saying that the two light emitting elements 27 and 32 may be monolithically formed on one semiconductor chip and used. Also,
The same applies to the case where the second light emitting element is added in the first embodiment.

The excitation NA of the optical system is determined by the lateral magnification of the lens 15. The lateral magnification of the lens 15 is (excitation NA) /
(NA of the light source), the first light emitting element 27,
When a semiconductor laser element is used as the second light emitting element 32, NA = 0.7 of the light source and excitation NA = 0.3 are input to the above equation to obtain a lateral magnification of 0.43. Therefore, lens 1
5 is designed to be 0.43, the excitation NA of the optical system
Can be set to 0.3.

FIGS. 5 and 6 are top views of the depolarizer used in the optical transceiver module shown in FIG.

The depolarizer 31 used in the optical transceiver module of the present embodiment does not use a transparent plate, unlike the depolarizer 84 of the proposed example. The reason is that since the diameter of the optical fiber is as large as 300 μm or more, it is not necessary to stop the light to the diffraction limit. Therefore, the mold part 24
Is directly attached to the front side.

Further, the depolarizer 31 is provided with (2n−
1) A 2λ plate and a 90-degree optical rotation plate are formed of a liquid crystalline polymer film. The (2n-1) / 2λ plate can be formed of a polarizing film. Both materials are in the form of a film, and it is possible to form holes of an arbitrary shape by punching out a mold or laser ablation using an excimer laser. The (2n-1) / 2λ plate is formed by rotating its optical axis by 45 degrees with respect to the optical axis of the polarizing film 30 which is a polarization splitting element. Note that (2n-1)
N of the / 2λ plate is an integer.

In the figure, reference numeral 43 denotes a light beam, and reference numeral 42 denotes a hole. As proposed by the present inventor in Japanese Patent Application No. 10-8054, if the light intensity between two orthogonal polarization components is equally divided into two, the intensity of the light split by the polarization splitting element and incident on the light receiving element becomes Since the light does not depend on the polarization state of the incident light, the depolarizer 31 shown in FIGS. 5 and 6 is provided with a hole so as to satisfy the luminous flux area / 2 = the sum of the hole areas in order to equally divide the light intensity into two.

[0079]

As described above, according to the present invention,
Since the optical transceiver module uses a receptacle with an optical cable with a short optical fiber plug that cannot be detached, the shortest fiber length of the optical cable using a detachable plug can be set sufficiently long, and the received signal light transmitted through the POF can be sufficiently transmitted. Since the optical fiber can be randomly polarized, it is possible to prevent an optical cable having a short optical fiber from being attached and detached, and to prevent the reception efficiency from being extremely lowered.

Also, since SLDs and LEDs are slower than semiconductor laser elements, using SLDs and LEDs instead of semiconductor laser elements during low-speed transmission can increase power consumption and extend the life of semiconductor laser elements. Can be.

Further, since the light that has passed through the depolarizer is randomly polarized, the reception efficiency is extremely reduced when the optical fiber length is short, or the polarization state of the received signal light changes due to vibration of the optical fiber. It is possible to prevent the intensity of the received signal light from changing in accordance with the vibration of the optical fiber and reducing the S / N.

Further, a polarizing film is less expensive than a polarizing branching film, which can promote a reduction in the cost of the system.

In addition, the liquid crystalline polymer film is inexpensive, which can promote the cost reduction of the system.

In addition, the wavelength of the transmission signal light is switched according to the optical fiber used, and the excitation NA of the transmission optical system is changed.
Is set to be equal to or smaller than the smallest NA of the optical fiber using the optical fiber. Therefore, any optical fiber can use a sufficiently wide band of the optical fiber and can communicate using both the POF and PCF optical fibers.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an optical transceiver module according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of an optical device used in the optical transceiver module shown in FIG.

FIG. 3 is a configuration diagram of an optical transceiver module according to a second embodiment of the present invention.

FIG. 4 is a configuration diagram of an optical device used in the optical transceiver module shown in FIG.

5 is a top view of a depolarizer used in the optical transceiver module shown in FIG.

FIG. 6 is a top view of another depolarizer used in the optical transceiver module shown in FIG.

FIG. 7 is a side sectional view of a conventional optical transceiver module.

FIG. 8 is a configuration diagram of another optical transmission / reception module.

9 is a configuration diagram of a depolarizer used in the optical transceiver module shown in FIG.

10 is a configuration diagram of another depolarizer used in the optical transceiver module shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Optical transmission / reception module 11 Receptacle part 12 Plug handle part 13 Plug 14 Optical fiber 15 Lens 16 Drive integrated circuit 17 Amplification integrated circuit 18, 19 External input / output terminal 20 Optical device 21 Printed board 22 Light receiving element 23 Monitor light receiving element 24 Mold part Reference Signs 25 Electrode 26 Submount 27, 32 Light emitting device 28, 29 Slope 30 Polarizing film 31 Depolarizer 42 Hole 43 Light flux

Continued on the front page F term (reference) 2H037 AA01 BA02 CA13 DA03 DA04 DA05 DA15 DA36 5F088 BA03 BB01 EA09 JA13 JA14 5F089 AA01 BC16 CA20 GA10 5K002 AA05 AA07 BA02 BA04 BA07 BA13 BA14 BA21 BA32 DA05 DA42 FA01

Claims (15)

[Claims] 1. An optical transmitting / receiving module for performing bidirectional communication using a single-core optical fiber, comprising: a receptacle in which a plug of an optical cable having a short optical fiber length is not detachable; and a first light emitting linearly polarized light as transmission signal light. A light-emitting element for receiving the received signal light,
A polarization splitting element that splits the received signal light into two orthogonal polarization components, and the transmission signal light from the first light emitting element passes through the polarization splitting element without splitting, and then passes through the optical fiber. An optical transmitting and receiving module, wherein optical coupling is performed, signal light received from the optical fiber is split by the polarization splitting element, and is incident on the light receiving element. 2. An optical transmitting / receiving module for performing bidirectional communication using a single-core optical fiber, comprising: a receptacle in which an optical cable having a short optical fiber length is not detachable; and a first light emitting linearly polarized light as transmission signal light. A light-emitting element, a second light-emitting element that emits a transmission signal light, a light-receiving element that receives a reception signal light, and a polarization splitting element that divides the reception signal light into two orthogonal polarization components. The transmission signal light from the optical fiber is passed through the polarization splitting element without branching, and then optically coupled to the optical fiber.The reception signal light from the optical fiber is split by the polarization splitting element to the light receiving element. An optical transmission / reception module, which is incident. 3. An optical transmission / reception module for performing bidirectional communication using a single-core optical fiber, comprising: a receptacle to which a plug of an optical cable having a short optical fiber is detachable, and a first light emitting linearly polarized light as transmission signal light. A light-emitting element, a light-receiving element that receives the reception signal light, a polarization splitting element that divides the reception signal light into two orthogonal polarization components, and a depolarizer, and the transmission signal light from the first light-emitting element is: Pass through the polarization splitter without splitting,
After passing through the depolarizer, optically coupled to the optical fiber, the received signal light from the optical fiber, after passing through the depolarizer, is split by the polarization splitting element, and incident on the light receiving element. Optical transceiver module. 4. An optical transmission / reception module for performing bidirectional communication using a single-core optical fiber, comprising: a receptacle to which a plug of an optical cable having a short optical fiber is detachable, and a first light emitting linearly polarized light as transmission signal light. A light-emitting element, a second light-emitting element that emits a transmission signal light, a light-receiving element that receives a reception signal light, a polarization splitting element that divides the reception signal light into two orthogonal polarization components, and a depolarizer, The transmission signal light from the light emitting element passes without branching in the polarization splitting element, and after passing through the depolarizer, is optically coupled to the optical fiber, and the reception signal light from the optical fiber passes through the depolarizer. An optical transmission / reception module, wherein the optical transmission / reception module is branched by the polarization splitting element after passing, and is incident on the light receiving element. 5. The first light-emitting element comprises a semiconductor laser element, and the second light-emitting element comprises an SLD or an LED. When the transmission speed is 400 Mbps or more, optical communication is performed using the first light-emitting element. The optical transceiver module according to claim 2, wherein the optical communication is performed using the second light emitting element when the transmission speed is less than 400 Mbps. 6. The first light-emitting element comprises a light-emitting element that emits light having a wavelength of 850 nm, and the second light-emitting element comprises a light-emitting element that emits light having a wavelength of 650 nm, and has a transmission speed of 400 Mbps. In the above, optical communication is performed using the first light emitting element, and the transmission speed is 400 Mb.
The optical transceiver module according to claim 2, wherein optical communication is performed using the second light-emitting element at a speed of less than ps. 7. The depolarizer uses a (2n-1) / 2λ plate having a hole area satisfying a luminous flux area / 2 = sum of hole areas.
The optical transceiver module according to claim 3, wherein the optical axis is formed by rotating the optical axis by 45 degrees with respect to the optical axis of the polarization splitting element. 8. The optical transmitting and receiving module according to claim 3, wherein the depolarizer is formed by a 90-degree optical rotation plate having a hole satisfying a relation of light flux area / 2 = sum of hole areas. 9. The optical transceiver module according to claim 7, wherein the (2n-1) / 2λ plate or the 90-degree optical rotation plate is made of a liquid crystalline polymer film. 10. The optical transceiver module according to claim 1, wherein the polarization splitting element is formed by attaching a polarizing film to a slope. 11. The optical transceiver module according to claim 10, wherein said slope is formed of a mold resin. 12. The optical transmission / reception module according to claim 1, wherein the excitation NA of the transmission optical system is set to be equal to or smaller than the smallest NA among the optical fibers used. 13. An optical cable, comprising a POF or a PCF having a sufficiently long fiber with a removable plug attached to both ends of the receptacle of the optical transceiver module according to claim 1. 14. An optical cable comprising a POF or a PCF having plugs attached to both ends of a receptacle of the optical transceiver module according to claim 3 or 4. 15. The optical transceiver module according to claim 1, wherein the optical transceiver module is an optical transceiver module.
A one-core bidirectional optical communication system, comprising: the optical cable according to claim 1.