JPH06291730A - Optical communication device - Google Patents

Abstract

PURPOSE:To provide an optical communication device where a stable communication is made to be performed even when the loss of an optical transmission line is increased and decreased. CONSTITUTION:This device is provided with a light receiving monitor 17 detecting light receiving power of communication opposite stations 10 and 20 to be inputted in the optical communication devices of a base station 10 and a terminal station 20, respectively, via an optical fiber F and transmitting the detected power data to the communication opposite stations 10 and 20, and light emitting control circuits 18 and 18' adjusting the light emitting power of the light communication device based on light receiving power data transmitted from the light receiving monitor 17 of the communication opposite stations 10 and 20. By performing the detection of light emitting power on a communication opposite side and stabilizing the detection power of a light receiving element based on the detected value, a stable communication can be performed even when the loss of not only light emitting elements but also an optical transmission line are increased and decreased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is intended to stabilize the light intensity reaching a light receiving element by detecting the far power of light on the communication partner side and adjusting the output of the light emitting element based on the detected value. This enables stable communication even when the loss of the optical transmission line increases or decreases, not only for the light emitting element. For example, as a communication device that connects an underwater robot or a submersible work boat with a mother ship or a land base, it is difficult in the marine field. The present invention relates to an optical communication device suitable for use in an environment.

[0002]

2. Description of the Related Art An optical transmission system including an optical communication device having an optical communication means and performing communication via an optical transmission line, particularly, an optical transmission system using an optical fiber for the transmission line is a non-induction, non-crosstalk, wide band, It has been used in place of metal transmission systems in various fields due to its low loss, meticulousness and light weight.
In the marine field and the like, an optical fiber is compounded in the tow cable of an underwater robot or a submersible work ship, and it is used as a communication device for connecting a mother ship and a land base.

In the meantime, the optical communication device has the above-mentioned features, but on the other hand, the temperature characteristics of the light emitting element used in the optical transmitter are not so good, so that the optical communication device is affected by changes in ambient temperature and changes with time. The output power of the light emission becomes unstable, and a communication error may occur.

Therefore, as shown in FIG. 4, an optical sensor 1 is provided in the optical transmitter, and the light emitting element 1'is provided by the sensor 1.
A part of the optical output of is taken out as monitor light, it is compared with the reference value, and the bias current is adjusted by the comparison value,
Conventionally, a method of obtaining a stable light emission output by applying feedback to the light output has been performed.

[0005]

However, in the method of detecting the light emission power of the light emitting element in the optical transmitter and stabilizing the light emission power by the detected value, the optical transmission line connecting the optical communication devices is not provided. When a transmission loss occurs, there is a problem that the received light power input to the optical receiver increases or decreases, resulting in a communication error.

In particular, in the above-mentioned marine field in which an optical fiber is combined with a tow cable and used in a harsh environment, a bending pressure due to an external force such as a pulling force or a tidal current at the time of towing is always applied to the optical fiber. Microbend loss that causes conversion between the guided mode and the radiated mode of the optical fiber occurs, causing transmission loss. Furthermore, it is difficult to identify the occurrence of this loss because the extent and frequency of occurrence of this loss are subtly different due to changes in the ambient temperature of the towing cable and changes in the water pressure and tension applied to the towing cable.
There is a problem that it is difficult to prevent.

Further, at this time, there is a problem that the light emission power cannot be adjusted as long as an underwater device such as an underwater robot or a submersible work boat is underwater even if a variation in the light reception power is detected on the mother ship.

Therefore, an object of the present invention is to adjust the emission power even when the optical transmission line causes a communication loss without causing a communication error and the optical communication device in which the variation of the emission power has occurred is underwater. It is possible to prevent the occurrence of communication errors, and particularly to provide an optical communication device suitable for use in the marine field where the use environment is severe.

[0009]

According to the present invention, in order to solve the above-mentioned problems, an underwater terminal station and an underwater base station which have optical communication means and are connected via an optical transmission line are provided. Light receiving monitor means for detecting the received light power from the communication partner station input through the optical transmission line and transmitting the detected power data to the communication partner station, and based on the received light power data transmitted from the communication partner station The control means for adjusting the emission power of the optical communication means is provided.

At this time, the control means may adjust the light emission power of the optical communication means based on the light reception power data transmitted from the communication partner station to keep the light reception power of the communication partner station constant. good.

Further, at this time, the terminal station may be provided with adjusting means for adjusting the light emission power of the optical communication means based on a command from the base station.

The above-mentioned base station on the surface of the water is connected to, for example, a ship floating on the surface of the water, an offshore base such as an oil digging station provided on a platform rising from the surface of the water, and an underwater terminal station provided on land. Including land-based base stations.

Further, "below the water surface" includes the water surface.

[0014]

In the optical communication device configured as described above, when the monitor means detects the received light power input through the optical transmission line, the change in the light emission output of the optical transmitter means of the base station and the terminal station, The transmission loss of the optical transmission line connecting the base station and the terminal station is detected, and the detected value is converted into data and transmitted. Therefore, the accurate loss data is transmitted regardless of the level fluctuation due to the transmission loss of the optical transmission line.

Further, the received light power data thus transmitted is inputted to the control means, and the control means always adjusts the light emission output of the optical communication means to an appropriate state by the inputted data.

At this time, the control means adjusts the light emission power of the optical communication means based on the light reception power data transmitted from the communication partner station so as to keep the light reception power of the communication partner station constant. , A feedback loop including the loss of the light emitting element and the optical transmission line is formed between the base station on the surface of the water and the terminal station on the surface of the water, and the light receiving power received by the base station and the terminal station is kept constant. As a result, the communication state is optimally maintained and stabilized.

Further, at this time, in the case where the above-mentioned terminal station is provided with the adjusting means for adjusting the light emitting power of the optical communication means based on the instruction from the base station, the light emitting power of the terminal station under the water surface is Adjustment can be easily performed by remote control from the base station.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an optical communication device of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, in this embodiment, the optical communication device according to the present invention is connected to a mother ship 2 and a towing cable 3 to form an underwater robot or an underwater working ship (hereinafter referred to as an underwater device) 4.
An embodiment used as a communication device between and is shown.

As shown in the circuit block diagram of FIG.
The optical communication device of this embodiment includes a base station 10 loaded on a mother ship 2 and a terminal station 20 loaded on an underwater device 4, both of which are optical fibers F combined with a tow cable 3.
Are connected by an optical transmission line. Also, the base station 1
0 and the terminal station 20 have an optical transmission means 30 and an optical reception means 40, respectively, and are configured to perform bidirectional communication.

The optical transmission means 30 includes a signal multiplexer (MI).
X) 11, an electric → optical converter (hereinafter referred to as E / O converter) 12 and a bidirectional demultiplexer / multiplexer (WDM) 13, and the optical receiving means 40 includes a signal demultiplexer (DIV) 14 and an optical receiver. → It is composed of an electric converter (hereinafter referred to as an O / E converter) 15 and a bidirectional demultiplexer-multiplexer (WDM) 13. Further, the base station 10 and the terminal station 20 are provided with a light emission monitor 16, a light reception monitor 17, and light emission control circuits 18 and 18 ', and further, the base station 10 is provided with an abnormality determination circuit 19.

The signal multiplexer 11 moves from the mother ship 2 to the underwater equipment 4
, For example, serial pulse transmission data and serial output data from the light receiving monitor 17 are input,
Both input data are multiplexed (for example, time division)
Then, the multiplexed input signal is input to the E / O converter 12.

The E / O converter 12 has, as a light emitting element, a laser diode (for the two-way communication, different wavelengths are used in the base station 10 and the terminal station 20), which is an electric-to-optical conversion circuit. And converts the input multiplexed data into an optical pulse train signal, and the bidirectional demultiplexer-multiplexer 1
Incident on 3. The E / O converter 12 is provided with a light emission monitor 16 including a light receiving circuit having a pin photodiode as a sensor and a V / F converter converting the circuit output into digital data. The light emitting power of the light emitting element of the container 12 is measured. In the base station 10, the output of the light emission monitor 16 is output from the abnormality determination circuit 1
9 to the signal multiplexer 11 at the terminal station 20.
Input to the output data of the light receiving monitor 17, the base station 10
It is multiplexed with the serial input data to the base station 10 and transmitted. Then, in the base station 10, the signal separator 1
It is separated by 4 and input to the abnormality determination circuit 19.

The bidirectional demultiplexer-multiplexer 13 performs bidirectional communication by wavelength division multiplexing, and transmits the multiplexed data incident from the E / O converters 12 of both stations 10 and 20 via the optical fiber F. And outputs to the O / E converter 15 of the opposite station.
The O / E converter 15 is composed of an optical-to-electrical conversion circuit using a pin photodiode as a light receiving sensor, converts an incident optical pulse train signal into a pulse train signal, and outputs the signal separator 14.
Output to. The O / E converter 15 is provided with a light receiving monitor 17 including a buffer circuit for taking out the output of the converting circuit and a V / F converter for digitally converting the taken out output level, and its output is a signal multiplex. The data is input to the device 11, multiplexed with the transmission data to the partner station, and transmitted. Further, the output of the light reception monitor 17 is also input to the abnormality determination circuit 19 in the base station 10.

The base station side signal separator 14 separates the received light power data, the light emission power data and the transmission data from the multiplexed pulse train signal input from the O / E converter 15, and the transmission data is transmitted to the mother ship 2 Output to the terminal station, the received light power data, the light emission control circuit 18 and the abnormality determination circuit 19
To the abnormality determination circuit 19. Further, the terminal station side signal separator 14 separates the received power data of the base station and the transmission data from the multiplexed pulse train signal input from the O / E converter 15, and outputs the transmission data to the underwater device 4. Then, the received light power data is output to the light emission control circuit 18 '.

The light emission control circuits 18 and 18 'compare the input received light power data with a reference value and adjust the bias current of the laser diode of the E / O converter 12 so as to eliminate the difference between the two. Adjust the output. Further, the light emission control circuit 18 'of the terminal station 20 decodes the command data sent via the base station 10 by being multiplexed with the serial transmission data from the mother ship side, and the reference value is set by the command data. Means for changing and adjusting means for adjusting the light emission power on the terminal station side are provided, and the reference value is changed by remote control from the base station 10,
The light emission power can be adjusted.

As described above, the abnormality determining circuit 19 receives the received light power data from the E / O converter 12 of the terminal station 20 detected by the light receiving monitor 17 of the base station 10 through the optical fiber F and the terminal station 20. Light emission power data of the terminal station 20 detected by the light emission monitor 16 of the base station 10 and E / O of the base station 10 detected by the light reception monitor 17 of the terminal station 20.
By comparing the received light power data from the converter 12 and the emitted light data of the base station 10 detected by the emission monitor 16 of the base station 10, whether the increase or decrease in the received light power is due to the loss of the optical fiber F, or It is determined whether or not it is due to the element, and a notification is given.

This embodiment is constructed as described above, and its operation will be described below.

The base station 10 and the terminal station 2 of this optical communication device
At 0, the light receiving monitor 17 causes O through the optical fiber F.
The level of the optical pulse incident on the / E converter 15 is detected, and the serial pulse signal A / D converted by the V / F converter is input to the signal multiplexer 11,
Along with the transmission data input to the signal multiplexer 11, each received light power data is always transmitted to the partner station.
Then, the transmitted received light power data is separated by the signal separator 14, and the light emission control circuit 18,
18 'is input. Emission control circuit 18, 1
8'compares the received light power data inputted with a preset reference value, and changes the bias current of the laser diode of the E / O converter 12 so as to eliminate the difference between the two, thereby changing the light emission output. By doing so, the gain of the optical pulse signal input through the optical fiber F and received by the O / E converter 15 is adjusted so as to maintain a margin in which no communication error occurs. At this time, the reference value of the terminal station 20 below the surface of the water can be easily set by remote control according to command data from the base station 10.

In the terminal station 20, the E / O converter 12
The light emission power of is detected by the light emission monitor 16, is digitally converted and input to the signal multiplexer 11, and is transmitted to the base station 10 together with the light reception power data and the transmission data, and the transmitted light emission power data is a signal separator. It is separated by 14, and is input to the abnormality determination circuit 19.

Similarly, the light emission power of the E / O converter 12 of the base station 10 is also detected by the light emission monitor 16, digitally converted and input to the abnormality determination circuit 19, and at the same time, O
The detection data of the light receiving monitor 17 of the / E converter 15 is also input to the abnormality determination circuit 19, and the abnormality determination circuit 19 compares the input data with each other to determine the transmission abnormality. Now, as described above, the light receiving powers of the other stations are detected with each other, and the light emitting powers of the E / O converters 12 are adjusted respectively. Therefore, when pressure is applied to the combined optical fiber F to change the guided mode and a transmission loss occurs and the transmission margin changes, the base station 10 and the terminal station 20 are changed in accordance with the change in the transmission loss. The light receiving power detected by the light receiving monitor 17 changes. The detected power data is signal multiplexer 11 → E / O
The received light power data transmitted to the converter 12 → optical fiber F → O / E converter 15 → signal separator 14 and separated by the signal separator 14 are emission control circuits 18 and 18 ′.
To the reference value, and the emission output of the E / O converter 12 is increased or decreased so that the difference becomes 0. Then,
The detection value of the received light power detected by the partner station increases or decreases. Then, the increased or decreased received light power is transmitted to the partner station in the same manner as described above and compared with the reference value by the emission control circuits 18 and 18 ', and the above operation is performed so that the difference becomes zero. Repeatedly, the optimum received light power is maintained. At this time, the abnormality determination circuit 19 causes the O of the terminal station 20 to be transmitted to the base station 10.
Since the value of the received light power of the / E converter 15 and the value detected by the light emission monitor 16 of the base station 10 are different from each other by the amount equivalent to the normal transmission loss, it is specified that the optical fiber F has a loss. It can also be judged from the data of its reverse system.

Also, for example, when the light emission output of the laser diode of the E / O converter 12 of the terminal station changes,
Similar to the above, the change is detected by the light receiving monitor 17 of the base station, and the detected data is the signal multiplexer 11 → E.
The light-emission control circuit 1 transmits the signal from the I / O converter 12 to the optical fiber F to the O / E converter 15 to the signal separator 14.
8 ', is compared with a reference value, and the light emission output of the E / O converter 12 is adjusted so that the difference becomes 0.
The light emission output of the O converter 12 is stabilized, and the optimum light receiving power is maintained. At this time, the abnormality determination circuit 19 detects the change in the light emission power of the E / O converter 12 of the base station 10 detected by the light emission monitor 16 of the base station 10 and the change of the light emission power detected by the light emission monitor 16 of the terminal station 20. By comparison, it is specified that the output change of the laser diode of the terminal station 20 whose emission power is controlled has occurred.

Further, even when the loss of the optical fiber F and the output change of the laser diode (for example, on the base station side) occur at the same time and the light receiving power of the light receiving monitor 17 changes, the detection data is also signal multiplexed. Device 11 → E / O converter 12 → optical fiber F → O / E converter 15 → signal separator 1
The light reception power is maintained in an optimum state by being transmitted from the 4 → emission control circuit 18, 18 ′ → E / O converter 12. At this time, the abnormality determination circuit 19 determines that the base station 1
The light reception power from the E / O converter 12 of the terminal station 20 detected by the light reception monitor 17 of 0 and the difference between the value detected by the light emission monitor 16 of the terminal station 20 and the normal light loss amount are compared, The loss of the fiber F is identified, the value detected by the light receiving monitor 17 of the terminal station 20 is compared with the light emitting power detected by the light emitting monitor 16 of the base station 10, and the output change of the laser diode on the base station side is compared. Specify.

As described above, in this optical communication device, the light receiving power can be always maintained constant by following the change in the loss of the optical fiber F and the change in the output of the light emitting element. It is possible to reduce the decrease in gain due to the transmission loss of F at the same time and reduce the communication error.

Although the towing body such as the mother ship 2 and the underwater device 4 has been described in the above embodiment, the present invention is not limited to this. For example, as shown in FIG. 3, a land base 5 and a plurality of seabeds are provided. It may be used for connecting to the station 6 or for a submarine cable.

[0036]

[Effect] The present invention is configured as described above, and even when the output of the light emitting element fluctuates or a loss occurs in the optical transmission line, the emission power is constantly controlled to always receive light of a constant level (range). Since power can be received, stable communication is possible even when the output of the light emitting element fluctuates or a loss occurs in the optical transmission line.

Therefore, it is particularly effective to use under a condition where loss fluctuation is likely to occur due to tension or lateral pressure, such as in the case where the optical transmission line is combined in the tow cable.

Further, since the emission power can be adjusted by remote control, one side of the communication device is installed in water or the like, which is suitable for use in a communication device that cannot always be maintained.

[Brief description of drawings]

FIG. 1 is a diagram showing a usage pattern of an embodiment.

FIG. 2 is a circuit block diagram of an embodiment.

FIG. 3 is another usage pattern diagram of the embodiment.

FIG. 4 is a block diagram of a conventional example.

[Explanation of symbols]

 10 base station 11 signal multiplexer 12 E / O converter 13 bidirectional demultiplexer-multiplexer 14 signal separator 15 O / E converter 16 light emission monitor 17 light reception monitor 18, 18 'light emission control circuit 20 terminal station 30 optical transmission Means 40 Optical receiving means F Optical fiber

Claims (3)

[Claims] 1. An optical communication device for connecting a terminal station under the water surface and a base station on the water surface, wherein the base station and the terminal station have optical communication means and are connected via an optical transmission line. Light receiving monitor means for detecting the received light power from the communication partner station which is input through the optical transmission line and transmitting the detected power data to the communication partner station, and the light reception monitor transmitted from the communication partner station. An optical communication device comprising control means for adjusting light emission power of optical communication means based on power data. 2. The control means adjusts the light emission power of the optical transmission means based on the light reception power data transmitted from the communication partner station to keep the light reception power of the communication partner station constant. Item 1. The optical communication device according to item 1. 3. The optical communication apparatus according to claim 1, wherein said terminal station is provided with adjusting means for adjusting the light emission power of the optical communication means based on a command from the base station.