JPH0998135A - Optical transmitter-receiver and optical transmission/ reception system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make an optical transmitter-receiver low in loss, small in size and low in cost by reducing the intensity loss of an optical signal in the branching part of a path for transmission and a path for reception for the optical signal. SOLUTION: When transmitting an optical signal for transmission emitted from a laser light source 11 to an optical fiber 16, an impressing voltage variable power source 14 impresses a voltage having a refractive index n1 for a liquid crystal panel 13 to transmit the optical signal for transmission to the liquid crystal panel 13. Thus, the optical signal for transmission is transmitted through the liquid crystal panel 13 and converged to the optical fiber 16 ith the extremely reduced loss. When receiving an optical signal for reception emitted from the optical fiber 16, the impressing voltage variable power source 14 impresses a voltage having a refraction factor n2 for the liquid crystal panel 13 to fully reflect the optical signal for reception toward a light receiving element 19 to the liquid crystal panel 13. Thus, the optical signal for reception arrives at the light receiving element 19 with the extremely reduced loss.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical transmitter / receiver connected to a transmission line made of an optical fiber for receiving and transmitting an optical signal, and an optical transmitter / receiver system using the optical transmitter / receiver.

[0002]

2. Description of the Related Art Wavelength division multiplexing (WDM) of light
vision multiplexing) transmission not only increases the transmission capacity of the optical transmission / reception system, but also enables bidirectional transmission and simultaneous transmission of different types of signals, which can meet the flexible service requirements of the optical transmission / reception system. It can be applied to various optical transmission / reception systems such as a transmission system, a subscriber system, and a local transmission system.

In particular, a subscriber optical transmission / reception system for transmitting data, multi-channel video information and the like from an optical transmission / reception base station to a general home through a transmission line made of an optical fiber has been proposed and studied. In a subscriber optical transmission / reception system, a plurality of light receiving devices for simultaneously receiving different wavelength-multiplexed optical signals and a light emitting device for sending a request or data from a home to a transmitting / receiving base station are subscribers. It is necessary to be equipped in the terminal for use.

Therefore, in the conventional subscriber optical transmission / reception system, a transmission optical signal having a wavelength of 1.3 μm, for example, is used at the time of transmission and a reception optical signal having a wavelength of 1.5 μm is used at the time of reception.

[0005]

However, at present, as a means for directly amplifying an optical signal, a wavelength of 1.5 μm is used.
Only an optical amplifier for amplifying m light has been developed. Therefore, there is a problem that the intensity of the transmission optical signal having a wavelength of 1.3 μm used at the time of transmission is greatly reduced when passing through the optical amplifier for amplifying the reception optical signal having a wavelength of 1.5 μm in the reverse direction.

Therefore, in order to surely amplify the optical signal, it is necessary to use an optical signal having a wavelength of 1.5 μm both during transmission and during reception. However, there is a problem that an optical signal having a wavelength of 1.5 μm is distorted when it is transmitted over a long distance. Therefore, light having a wavelength of 1.3 μm is preferable as the optical signal used in the optical transmission / reception system.

Therefore, the wavelength of 1.3 is used for both transmission and reception.
In order to be able to use an optical signal of μm, an optical transmission / reception system as shown in FIG. 5 was considered.

In FIG. 5, reference numeral 51 is a laser light source, 52 is a transmitting side lens system, 53 is a 3 dB coupler, 54 is an optical fiber, 55 is a light receiving element, and 56 is a receiving side lens system.
In the optical transmission / reception system shown in FIG. 5, since the transmission optical signal transmitted from the home to the transmission / reception base station and the reception optical signal transmitted from the transmission / reception base station to the home are bidirectionally transmitted, It is necessary to split the optical signal and the receiving optical signal. Therefore, in the above optical transmission / reception system, the 3 dB coupler 53 is arranged at the branch portion between the transmission path for transmitting the transmission optical signal and the reception path for transmitting the reception optical signal.

At the time of transmission, the optical signal for transmission emitted from the laser light source 51 passes through the lens system 52 on the transmission side,
It is incident on the optical fiber 54 via the 3 dB coupler 53, and then transmitted to the transmitting / receiving base station. In addition, at the time of reception, the reception optical signal output from the transmission / reception base station is emitted from the optical fiber 54, then passes through the 3 dB coupler 53, passes through the reception side lens system 56, and is focused on the light receiving element 55. It

By the way, the 3 dB coupler 53 is
The light incident on the B coupler 53 is split into two output ports, each split by 50% and output. Therefore, at the time of transmission, at most 50% of the transmission optical signal emitted from the laser light source 51 is incident on the optical fiber 54, and at the time of reception, 50% of the reception optical signal emitted from the optical fiber 54. The following optical signals only reach the light receiving element 55.

In this way, when the optical signal is branched by the 3bB coupler 53, the problem that the intensities of the transmitting optical signal and the receiving optical signal are greatly lowered cannot be avoided.

[0012] However, if a laser light source that outputs a stronger optical signal is used, it is possible to compensate for the decrease in the optical signal for transmission, but for this purpose, a high-output laser light source is required and the cost is high. Therefore, it is not suitable for an optical transmitter / receiver installed in each home.

Further, in order to improve the light receiving sensitivity, it is considered to increase the intensity of the transmitting optical signal output from the transmitting / receiving base station, but in the case of a high output optical signal, it is generated in the optical fiber. Since the quality of the optical signal deteriorates due to a non-linear phenomenon, that is, Brillian scattering or Rayleigh scattering, there is a problem that the optical signal is deteriorated when transmitting the optical signal such as video information. Therefore, it is difficult to transmit a high-power optical signal for transmission from the transmission / reception base station.

In view of the above, the present invention can realize low loss, downsizing, and cost reduction by reducing the intensity loss of the optical signal at the branch portion between the optical signal transmission path and the optical signal reception path. An object of the present invention is to provide an optical transmitter / receiver and an optical transmitter / receiver system using the optical transmitter / receiver.

[0015]

According to a first aspect of the present invention, there is provided an optical transmitter / receiver, a light emitting means for outputting an optical signal for transmission, and an optical signal for reception output from a transmitting / receiving base station. Is disposed at a branch portion between the light receiving means, the transmission path through which the transmission optical signal is transmitted and the reception path through which the reception optical signal is transmitted, and the refractive index changes the optical signal by the applied voltage. A refractive index varying means that is variable between a first refractive index for reflecting and a second refractive index for transmitting an optical signal; a first voltage such that the refractive index varying means has the first refractive index; The refraction index changing means is provided with an applied voltage variable power source for variably applying a second voltage having the second refraction index to the refraction index changing means.

According to the structure of claim 1, when the first voltage is applied to the refractive index variable means by the applied voltage variable power source, the refractive index of the refractive index variable means becomes the first refractive index for reflecting the optical signal. When a voltage of 2 is applied, the refractive index of the refractive index variable means becomes the second refractive index that allows the optical signal to pass therethrough, and the voltage applied to the refractive index variable means by the applied voltage variable power supply changes the optical signal path. You can choose. Therefore, when the second voltage is applied to the refractive index changing means to set the second refractive index, the optical signal for transmission output from the light emitting means is transmitted to the transmitting / receiving base station or is output from the transmitting / receiving base station. The received optical signal can be transmitted toward the light receiving means, and when the first voltage is applied to the refractive index varying means to make it have the first refractive index, the reception signal output from the transmitting / receiving base station is received. The optical signal for use can be reflected toward the light receiving means, or the optical signal for transmission output from the light emitting means can be reflected toward the transmitting / receiving base station.

According to a second aspect of the invention, the refractive index varying means in the structure of the first aspect is limited to the liquid crystal plate.

According to a third aspect of the present invention, a light emitting means for outputting a transmission optical signal having a predetermined polarization plane and a reception optical signal output from a transmission / reception base station are input to an optical transmission / reception device. The light receiving means, the transmission path for transmitting the transmission optical signal, and the reception path for transmitting the reception optical signal are arranged at a branching portion, and the transmission optical signal is transmitted. The liquid crystal plate is configured to reflect almost half of the reception optical signal toward the light receiving means.

According to the structure of claim 3, the liquid crystal plate has a property of transmitting light having a predetermined polarization plane, but substantially totally reflecting light having a polarization plane orthogonal to the predetermined polarization plane. , The liquid crystal plate disposed at the branch between the transmission path and the reception path transmits the optical signal for transmission and reflects almost half of the optical signal for reception toward the light receiving means. The light intensity of the optical signal is reduced to about half, but the light intensity of the transmission optical signal is hardly reduced.

According to a fourth aspect of the present invention, in the structure according to the third aspect, the liquid crystal plate transmits the transmitting optical signal and reflects almost half of the receiving optical signal toward the light receiving means. The configuration further includes a voltage power supply for applying a voltage having a different polarization plane to the liquid crystal plate.

According to the structure of claim 4, the liquid crystal plate transmits a light signal for transmission while a voltage having a polarization plane for reflecting almost half of the light signal for reception toward the light receiving means is generated by the voltage power supply. Since the liquid crystal plate can be applied to the plate, the liquid crystal plate is arranged so that it has an appropriate inclination angle with respect to the transmitting path and the receiving path, and then the voltage applied to the liquid crystal plate is controlled to cause the liquid crystal plate to transmit. It is possible to have a polarization plane that allows the credit optical signal to pass while reflecting almost half of the receiving optical signal toward the light receiving means.

According to the fifth aspect of the present invention, the solution means is provided on the subscriber side, and has a light emitting means for outputting a transmission optical signal and a light receiving means for receiving a reception optical signal. A transmission / reception base station that outputs the reception optical signal to the subscriber side transmission / reception device and receives the transmission optical signal output by the subscriber side transmission / reception device; the subscriber side transmission / reception device; Provided between a transmission / reception base station and an optical transmission / reception system including an optical fiber for transmitting the transmission optical signal and the reception optical signal, the subscriber-side transmission / reception device is configured such that the transmission optical signal is It is provided at a branch portion between a transmission path to be transmitted and a reception path to which the reception optical signal is transmitted, and has a refractive index of one of the transmission optical signal and the reception optical signal depending on an applied voltage. First refraction to reflect And a second index of refraction that allows the other of the optical signal for transmission and the other optical signal for reception to pass therethrough, and the index variable means provided in the subscriber-side transceiver device. Variable applied voltage for variably applying to the refractive index variable means a first voltage having the first refractive index and a second voltage having the second refractive index variable means. And a power supply.

According to the structure of claim 5, like the structure of claim 1, since the path of the optical signal can be selected by changing the voltage applied to the refractive index variable means by the applied voltage variable power source, the refractive index variable means. It is possible to transmit the optical signal incident on the optical disc in an appropriate direction without reducing the light intensity.

According to the sixth aspect of the present invention, a means for solving the problem is provided on the subscriber side, and has a light emitting means for outputting an optical signal for transmission and a light receiving means for receiving an optical signal for reception on the subscriber side. A transmission / reception base station that outputs the reception optical signal to the subscriber side transmission / reception device and receives the transmission optical signal output by the subscriber side transmission / reception device; the subscriber side transmission / reception device; Provided between a transmission / reception base station and an optical transmission / reception system including an optical fiber for transmitting the transmission optical signal and the reception optical signal, the subscriber-side transmission / reception device is configured such that the transmission optical signal is It is provided at a branch portion between a transmission path to be transmitted and a reception path to which the reception optical signal is transmitted, and transmits the transmission optical signal toward the optical fiber, while receiving the reception optical signal. Almost half of It is an arrangement which has a liquid crystal plate for reflecting towards the light receiving means.

According to the structure of claim 6, similarly to the structure of claim 3, the liquid crystal plate arranged at the branch portion between the transmission path and the reception path transmits the transmission optical signal while receiving the reception light. Since almost half of the signal is reflected toward the light receiving means, the light intensity of the reception light signal is reduced to about half, but the light intensity of the transmission light signal is hardly reduced.

[0026]

DETAILED DESCRIPTION OF THE INVENTION An optical transmitter / receiver according to an embodiment of the present invention will be described below.

[First Embodiment] FIG. 1 shows a schematic configuration of an optical transmitter / receiver according to a first embodiment of the present invention.

In FIG. 1, 11 is a laser light source that emits light having a wavelength of 1.3 μm, 12 is a first collimating lens that converts the optical signal for transmission emitted from the laser light source 11 into parallel light, and 13 is applied. A liquid crystal plate that transmits or totally reflects an optical signal by a voltage, and the liquid crystal plate 13 forms a predetermined angle with respect to the light transmission path and the light reception path at a branch portion of the light transmission path and the light reception path. It is arranged so that it can be tilted. Further, in FIG. 1, 14 is a liquid crystal plate 1.
A variable applied voltage power source capable of applying different voltages to 3, a second collimating lens 15 for collecting parallel light,
Reference numeral 16 is an optical fiber that propagates an optical signal having a wavelength of 1.3 μm in a single mode, 17 is a transmission / reception base station that receives a transmission optical signal and outputs a reception optical signal, and 18 is a liquid crystal output from the transmission / reception base station 17 A third collimator lens that collects the parallel light totally reflected by the plate 13, and 19 is a light receiving element that receives a reception optical signal, and is the laser light source 1 described above.
1, the liquid crystal plate 13 and the light receiving element 19 constitute an optical transceiver.

The operation of the optical transceiver according to the first embodiment will be described below.

First, when transmitting the transmission optical signal emitted from the laser light source 11 to the optical fiber 16,
The applied voltage variable power supply 14 applies a first voltage to the liquid crystal plate 13 so that the liquid crystal plate 13 has a refractive index n ₁ that allows the transmission optical signal to pass therethrough. As a result, the optical signal for transmission is transmitted through the liquid crystal plate 13 with very little loss, and the optical fiber 16 is transmitted.
Is focused on.

Next, when the receiving optical signal emitted from the optical fiber 16 is received, the applied voltage variable power supply 14
A second voltage is applied to the liquid crystal plate 13 so that the liquid crystal plate 13 has a refractive index n ₂ that totally reflects the reception optical signal toward the light receiving element 19. As a result, the optical signal for reception reaches the light receiving element 19 with very little loss.

The liquid crystal plate 13 does not change the tilt angle with respect to the optical axis during both transmission and reception,
The effective refractive index is controlled by the magnitude of the applied voltage. Specifically, the arrangement of molecules in the liquid crystal plate 13 is controlled by the voltage applied to the both surfaces of the liquid crystal plate 13 by the variable voltage source, and the effective refractive index of the liquid crystal plate 13 is changed by the change in the arrangement of the molecules. Is controlled.

FIG. 2 shows the relationship between the voltage applied to the liquid crystal plate 13 and the effective refractive index of the liquid crystal plate 13. In FIG. 2, the vertical axis represents the refractive index and the horizontal axis represents the voltage. As is apparent from FIG. 2, the effective refractive index of the liquid crystal plate 13 changes to 0.3 or more when the voltage applied to the liquid crystal plate 13 is 0V and 20V.

The tilt angle θ of the substrate of the liquid crystal plate 13, the liquid crystal plate 13
There is a relationship of sin θ = n _t / n _θ between the effective refractive index n _θ and the refractive index n _t (= 1) of air. Therefore, if the effective refractive index of the liquid crystal plate 13 is 1.5, the tilt angle θ of the liquid crystal plate 13 is 41.81 °, and the tilt angle θ is 41.91 °.
With the above, the liquid crystal plate 13 can totally reflect light.

In the first embodiment, the liquid crystal plate 13 is used as means for changing the refractive index of light.
Instead of this, an organic material, glass, solid, or liquid whose refractive index changes depending on the applied voltage can be appropriately used.

In the first embodiment, the liquid crystal plate 13 is arranged so as to transmit the optical signal for transmission and totally reflect the optical signal for reception. It may be arranged so that the optical signal is totally reflected while the receiving optical signal is transmitted.

[Second Embodiment] FIG. 3 shows a schematic configuration of an optical transmitter / receiver according to a second embodiment of the present invention.

In FIG. 3, reference numeral 21 is a laser light source for emitting light having a wavelength of 1.3 μm, 22 is a first collimating lens for making the transmission optical signal emitted from the laser light source 21 parallel light, and 23 is applied. The liquid crystal plate 13 is a liquid crystal plate that changes the polarization plane direction of light to be passed by a voltage, and the liquid crystal plate 13 is arranged so as to be inclined at a predetermined angle with respect to the light transmission path and the light reception path. In addition, in FIG.
Reference numeral 4 denotes an applied voltage variable power source capable of applying different voltages to the liquid crystal plate 23, 25 a second collimating lens for condensing parallel light, and 26 light for propagating an optical signal having a wavelength of 1.3 μm in a single mode. A fiber, 27 is a transmission / reception base station for receiving a transmission optical signal and outputting a reception optical signal, 28
Is a third collimating lens for collecting parallel light output from the transmitting / receiving base station 27 and reflected by the liquid crystal plate 23, 29
Is a light receiving element that receives the optical signal for reception.

The operation of the optical transmitter / receiver according to the second embodiment will be described below. As a premise, the characteristics of the optical fiber 26 and the liquid crystal plate 23 will be described.

When the optical signal propagates through the optical fiber 26, the plane of polarization is not controlled, so the optical signal emitted from the optical fiber 26 has a plane of polarization in random directions. Therefore, although the light emitted from the optical fiber 26 is linearly polarized light, its polarization plane is not fixed. On the other hand, the liquid crystal plate 23 transmits light having a first polarization plane which is a predetermined polarization plane, but almost totally reflects light having a second polarization plane which is a polarization plane orthogonal to the first polarization plane. .

First, the applied voltage variable power source 24 is the liquid crystal plate 2
A voltage is applied to the liquid crystal plate 23 so that 3 has a polarization plane direction that allows the light emitted from the laser light source 21 to pass therethrough.
In this way, the transmission optical signal emitted from the laser light source 21 is transmitted through the liquid crystal plate 23 and condensed on the optical fiber 26 with very little loss.

On the other hand, the receiving optical signal emitted from the optical fiber 26 is emitted from the optical fiber 26 with the polarization planes in random directions as described above, so that almost half of the receiving optical signal is the liquid crystal plate. The other half of the light is transmitted by the liquid crystal 23 and is reflected by the liquid crystal plate 23 to reach the light receiving element 29.

According to the second embodiment, about half the light is lost in the receiving optical signal as compared with the first embodiment, but it is not necessary to perform the switching operation by the applied voltage variable power supply 24.

[Third Embodiment] FIG. 4 shows a schematic configuration of an optical transmission / reception system for performing bidirectional wavelength division multiplexing optical transmission according to a third embodiment of the present invention. In this bidirectional wavelength division multiplexing optical transmission system, a branching device, an optical amplifier, and other components of the transmission line provided between the optical transmission / reception device for performing bidirectional optical transmission and the transmission / reception base station are omitted. ing.

In FIG. 4, 31 is a laser light source that emits light having a wavelength of 1.3 μm, 32 is a first collimating lens that converts the transmission optical signal emitted from the laser light source 31 into parallel light, and 33 is applied. A liquid crystal plate that transmits or totally reflects an optical signal according to a voltage, and 34 is an applied voltage variable power supply that can apply different voltages to the liquid crystal plate 33. The laser light source 31, the liquid crystal plate 33, and the applied voltage variable The power supply 34 has the same function as that of the first embodiment. In FIG. 4, 35 is a second collimating lens that collects parallel light, 36 is an optical fiber that propagates an optical signal with a wavelength of 1.3 μm in a single mode, 37 is a coupler, 38 is a digital signal generator, and 39 is In the digital signal receiving apparatus, a coupler 37, a digital signal generating apparatus 38, and a digital signal receiving apparatus 39 constitute a transmitting / receiving base station. Further, in FIG. 4, reference numeral 40 denotes a third collimating lens for collecting parallel light output from the digital signal generator 38 and totally reflected by the liquid crystal plate 33, reference numeral 41 denotes a light receiving element for receiving a reception optical signal, and 42 denotes A receiving side signal generating device that outputs a signal based on the receiving optical signal received by the light receiving element 41, and 43 is a receiving side signal generating device 42.
It is a transmission side signal generator that outputs a control signal to the laser light source 31 and the applied voltage variable power supply 34 when receiving a signal from the.

The operation of the optical transmission / reception system according to the third embodiment will be described below.

First, at the time of reception, the transmission optical signal output from the digital signal generator 38 of the transmission / reception base station is transmitted to the reception side by the optical fiber 36, and then the liquid crystal plate 33.
Is reflected by and reaches the light receiving element 41.

On the other hand, when, for example, a service request signal to the transmitting / receiving base station is input to the transmitting side signal generating device 43, the transmitting side signal generating device 43 causes the laser light source 31 to output the transmitting optical signal and the applied voltage can be varied. A control signal is output to the power supply 34 to control the liquid crystal plate 33 so that the transmission optical signal is transmitted. In this way, the transmitting optical signal reaches the digital signal receiving device 39 of the transmitting / receiving base station after being transmitted through the optical fiber 36.

In the conventional bidirectional optical transmission / reception system, the time domain main multiplex is mainly used.
access, etc. are adopted, the optical signal for reception output from the transmission / reception base station is transmitted during a certain predetermined time zone, and the optical signal for transmission from the optical transmission / reception device installed at home during another predetermined time zone. In order to transmit the optical signal, it is controlled in which direction the optical signal is transmitted depending on the time zone. For this reason,
There is a problem that the transmission optical signal cannot be transmitted in the time period in which the reception optical signal is transmitted, and the reception optical signal cannot be transmitted in the time period in which the transmission optical signal is transmitted.

However, in the optical transmission / reception system according to the third embodiment, when the transmission end signal is automatically added after the reception optical signal transmitted from the transmission / reception base station, the optical transmission / reception system is installed in a home or the like. In the optical transmitter / receiver, when the light receiving element 41 receives the signal indicating the end of transmission, the receiver side signal generator 42 outputs a service request signal to the transmitter / receiver base station to the transmitter side signal generator 43, for example. By doing so, the liquid crystal plate 33 and the applied voltage variable power supply 34 operate, and the service request signal is output to the transmitting / receiving base station. On the other hand, when there is no service request signal, the reception side signal generation device 42 outputs a standby signal to the transmission side signal generation device 43. By doing so, the liquid crystal plate 33 and the applied voltage variable power supply 34 are in a standby state.

In this way, the transmission state or the standby state of the liquid crystal plate 33 and the applied voltage variable power source 34 can be controlled by the signal output from the reception side signal generator 42 based on the reception optical signal received by the light receiving element 41. Therefore, the signal waiting time is significantly shortened, and more efficient bidirectional optical communication can be realized.

[0052]

According to the optical transmitter / receiver of the first aspect of the present invention, since the optical signal path can be selected by changing the voltage applied to the refractive index varying means by the applied voltage varying power source, the refractive index varying means can be used. Since the incoming optical signal can be transmitted in an appropriate direction without reducing the optical intensity, reduction of the optical intensity of the optical signal for transmission output from the home side to the transmitting / receiving base station can be avoided, resulting in low loss of the optical transceiver. It is possible to achieve size reduction, size reduction, and price reduction.

According to the optical transmitter / receiver of the second aspect of the present invention, since the refractive index changing means is limited to the liquid crystal plate, the voltage applied to the liquid crystal plate is changed by the applied voltage variable power source to ensure the path of the optical signal. Can be selected.

According to the optical transmitter-receiver of the third aspect of the present invention, the liquid crystal plate arranged at the branch portion between the transmission path and the reception path allows the transmission optical signal to pass therethrough, while Since almost half of the light intensity is reflected toward the light receiving means, the light intensity of the reception optical signal is reduced to about half, but the light intensity of the transmission optical signal is hardly reduced. It is possible to avoid reduction of the light intensity of the output optical signal for transmission, and it is possible to reduce the loss, size, and cost of the optical transceiver.

According to the optical transmitter / receiver device of the fourth aspect, the liquid crystal plate is arranged so as to have an appropriate inclination angle with respect to the transmitting path and the receiving path, and then the voltage applied to the liquid crystal plate is controlled. This allows the liquid crystal plate to have a plane of polarization that allows transmission of the transmission optical signal and reflection of almost half of the reception optical signal toward the light receiving means. Even if there is an error in the tilt angle, the transmission optical signal can be reliably transmitted through the liquid crystal plate, and almost half of the reception optical signal can be reliably reflected toward the light receiving means.

According to the optical transmission / reception system of the fifth aspect of the invention, as in the first aspect of the invention, the optical signal incident on the refractive index varying means can be transmitted in an appropriate direction without reducing the light intensity. Since it is possible to avoid reduction of the light intensity of the transmission optical signal output from the home side to the transmitting / receiving base station,
It is possible to reduce the loss, size, and cost of the optical transceiver.

According to the optical transmission / reception system of the sixth aspect of the present invention, the optical intensity of the optical signal for reception is reduced to about half, but the optical intensity of the optical signal for transmission is almost reduced as in the invention of the third aspect. Since it is not possible to reduce the optical intensity of the optical signal for transmission output from the home side to the transmitting / receiving base station,
It is possible to reduce the loss, size, and cost of the optical transceiver.

As described above, according to the inventions of claims 1 to 6, since it is possible to reduce the loss, size and cost of the optical transmitter / receiver, a relay transmission system, a subscriber system and a local transmission system are provided. It can greatly contribute to the construction of various optical fiber communication systems such as, and has an extremely large industrial utility value.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an optical transmission / reception device according to a first embodiment of the present invention.

FIG. 2 is a characteristic diagram showing a relationship between a voltage applied to a liquid crystal plate and an effective refractive index of the liquid crystal plate of the optical transceiver according to the first embodiment.

FIG. 3 is a schematic configuration diagram of an optical transmission / reception device according to a second embodiment of the present invention.

FIG. 4 is a schematic configuration diagram of an optical transmission / reception system according to a third embodiment of the present invention.

FIG. 5 is a schematic configuration diagram of an optical transmission / reception device which is a premise of the present invention.

[Explanation of symbols]

 11 Laser Light Source 12 First Collimating Lens 13 Liquid Crystal Plate 14 Applied Voltage Variable Power Supply 15 Second Collimating Lens 16 Optical Fiber 17 Transmitting / Receiving Base Station 18 Third Collimating Lens 19 Photoreceptor 21 Laser Light Source 22 First Collimating Lens 23 Liquid Crystal Plate 24 Applied Voltage Variable Power Supply 25 Second Collimating Lens 26 Optical Fiber 27 Transmitting / Receiving Base Station 28 Third Collimating Lens 29 Photoreceptor Element 31 Laser Light Source 32 First Collimating Lens 33 Liquid Crystal Plate 34 Applied Voltage Variable Power Supply 35 Second Collimator Lens 36 Optical fiber 37 Coupler 38 Digital signal generator 39 Digital signal receiver 40 Third collimating lens 41 Light receiving element 42 Receiver side signal generator 43 Transmitter side signal generator

Claims (6)

[Claims] 1. A light emitting means for outputting an optical signal for transmission, a light receiving means for receiving an optical signal for reception output from a transmission / reception base station, a transmission path for transmitting the optical signal for transmission, and the reception. It is placed at the branch with the receiving path where the optical signal is transmitted,
A refractive index that reflects an optical signal according to an applied voltage
Refractive index variable means that is variable between the second refractive index and the second refractive index that transmits an optical signal, and the first voltage and the refractive index variable means that the refractive index variable means has the first refractive index. An optical transmission / reception device, characterized in that the means includes a variable applied voltage power source that variably applies a second voltage having the second refractive index to the refractive index variable means. 2. The optical transceiver according to claim 1, wherein the refractive index varying means is a liquid crystal plate. 3. A light emitting means for outputting a transmission optical signal having a predetermined polarization plane, a light receiving means for receiving a reception optical signal output from a transmission / reception base station, and the transmission optical signal for transmission. Arranged at a branch portion between a transmission path and a reception path through which the reception optical signal is transmitted,
An optical transmission / reception device, comprising: a liquid crystal plate that transmits the transmission optical signal while reflecting approximately half of the reception optical signal toward the light receiving means. 4. The liquid crystal plate is provided with a voltage having a polarization plane such that the liquid crystal plate transmits the transmitting optical signal and reflects almost half of the receiving optical signal toward the light receiving means. The optical transceiver according to claim 3, further comprising a voltage power supply applied to the optical transceiver. 5. A subscriber side transmitting / receiving apparatus, which is provided on the subscriber side and has a light emitting means for outputting a transmitting optical signal and a light receiving means for receiving a receiving optical signal, and to the subscriber side transmitting / receiving apparatus. And a transmission / reception base station that outputs the reception optical signal and that receives the transmission optical signal output by the subscriber side transmission / reception device, and is provided between the subscriber side transmission / reception device and the transmission / reception base station, In an optical transmission / reception system including an optical fiber for transmitting the transmission optical signal and the reception optical signal, the subscriber-side transmission / reception device includes a transmission path through which the transmission optical signal is transmitted and the reception optical signal. Is arranged at a branch portion from a receiving path through which light is transmitted, and the refractive index is variable by a voltage applied to a first refractive index for reflecting an optical signal and a second refractive index for transmitting an optical signal. Rate changing means, The is rate varying means, such as having the first refractive index 1
And the applied voltage variable power source for variably applying to the refractive index varying means a second voltage such that the refractive index varying means has the second refractive index. Optical transceiver system. 6. A subscriber side transmitter / receiver provided on the subscriber side and having a light emitting means for outputting an optical signal for transmission and a light receiving means for receiving an optical signal for reception, and to the subscriber side transmitter / receiver. And a transmission / reception base station that outputs the reception optical signal and that receives the transmission optical signal output by the subscriber side transmission / reception device, and is provided between the subscriber side transmission / reception device and the transmission / reception base station, In an optical transmission / reception system including an optical fiber for transmitting the transmission optical signal and the reception optical signal, the subscriber-side transmission / reception device includes a transmission path through which the transmission optical signal is transmitted and the reception optical signal. Is arranged at a branching portion with respect to a reception path through which the optical signal is transmitted, and transmits the transmission optical signal toward the optical fiber, while reflecting almost half of the reception optical signal toward the light receiving means. liquid crystal Optical transmission and reception system, characterized in that it has a.