JP2001160651A - Semiconductor laser output control device and optical signal transmission system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a semiconductor laser output control device which can control adequately a laser light injected in an optical amplifier, corresponding to the number of channels of an optical signal, and an optical signal transmission system. SOLUTION: An optical signal outputted from a first transmitter 201 to an optical fiber up-transmission line 203 is inputted in a first erbium doped fiber 212, amplified by a backward excitation system, with a laser light outputted from a first pumping light output part 216, and sent out to a first receiver 202. An optical fiber down-transmission line has the same constitution. When the number of channels of the optical signal transmitted through the up-transmission line 203 changes, the first pumping light output part 216 changes the output level of a semiconductor laser which is outputted from the output part 216, corresponding to the change. Thereby the output of each channel of the optical signal after amplification can be maintained to be constant when the number of channels is increased or decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser output control device for controlling the output of a semiconductor laser and an optical signal transmission system using the same, and more particularly to a channel of an optical signal transmitted through a transmission line using an optical fiber. The present invention relates to a semiconductor laser output control device and an optical signal transmission system suitable for a case where the number changes.

[0002]

2. Description of the Related Art The output of a semiconductor laser fluctuates due to fluctuations in input voltage and ambient temperature. Therefore, conventionally, a semiconductor laser output control device has been used in which the output of a semiconductor laser is monitored by a light receiving element so as to eliminate output fluctuation.

FIG. 9 shows an outline of a circuit configuration of a conventionally used semiconductor laser output control device. The semiconductor laser output control device 101 shown in FIG.
A series circuit including a Zener diode 104 for setting a constant voltage between the two terminals 102 and 103 to a constant voltage, a monitor photodiode 105 and a resistor 106 connected in parallel with the Zener diode 104; It includes a resistor 107, a parallel circuit in which the semiconductor laser 108 and the collector-emitter of the transistor 109 are connected in parallel, and a series circuit in which each of the resistors 111 is connected in series. The connection point between the anode side of the monitoring photodiode 105 and the resistor 106 is connected to the input side of an APC circuit (automatic output control circuit) 112, and the APC circuit 11
The output side of 2 is connected to the base of transistor 109.

In such a conventional semiconductor laser output control device 101, a part of the light beam output from the semiconductor laser 108 is input to the monitoring photodiode 105. When the output of the semiconductor laser 108 fluctuates due to fluctuations in voltage or temperature, the detection level of the monitoring photodiode 105 also fluctuates accordingly. The input side of the APC circuit 112 has a voltage level obtained by dividing the voltage of the monitoring photodiode 105 and the resistance 106. Therefore, the APC circuit 112 inputs a signal of a voltage level corresponding to the light receiving level of the monitoring photodiode 105, and the transistor 1
09 collector-emitter current is varied. The semiconductor laser 108 and the collector-emitter of the transistor 109 are connected in parallel. Therefore, by controlling the current flowing between the collector and the emitter, the semiconductor laser 1 is controlled.
The value of the current flowing to the 08 side is controlled, and control is performed to keep the output constant. Japanese Patent Application Laid-Open Nos. Hei 6-338647 and Hei 6-164037 disclose the same technology.

By the way, in a transmission device using an optical fiber, by multiplexing optical signals of a plurality of different wavelengths and sending the multiplexed optical signal to the optical fiber, a single-channel system that handles only light of a single wavelength is used. The amount of signal to be transmitted can be dramatically increased as the number of channels increases. However, when an optical cable is initially laid on the sea floor or when an optical cable is added, signals of very few channels are often transmitted by one optical fiber when compared with the maximum number of channels.

[0006]

However, if a conventional semiconductor laser output control device as shown in FIG. 9 is used as an output device for injecting pump light into an erbium-doped fiber of an optical fiber, the semiconductor laser 108 As a result of the output laser light being monitored by the monitoring photodiode, control is performed such that the laser light is always at a constant level. Such control is
It is preferable when the number of channels of the optical signal directly amplified by the erbium-doped fiber is constant.
However, when the number of channels of optical signals transmitted simultaneously by the optical cable is gradually increased from the initially small number, even if the intensity of the laser light of each wavelength does not change, the monitor photodiode is not changed. The detection level of 105 increases. As a result, there is an inconvenience that control is performed such that the level of output light of each wavelength decreases as the number of channels of optical signals transmitted simultaneously through the optical cable increases. Of course, the same problem occurs when the number of channels is smaller than the current number.

Therefore, in the related art, when the number of wavelengths of multiplexed light (the number of channels) fluctuates so as to increase or decrease, the resistor 107 or the resistor 11 is used each time.
For example, the resistance value of No. 1 is adjusted to prevent a change in the level of output light of each wavelength. However, when an optical fiber is buried in the seabed or underground, it is necessary to readjust the resistance values of these resistors 107 or 111 at the junction of the cable. Was difficult.

For this reason, if it is difficult to adjust the resistance value in the past, an optical signal having a wavelength not yet used is also output as a dummy so that the number of channels to be used will be constant in the future. I was However, according to this method, for example, even in a system that currently requires transmission of only a few channels, it is necessary to transmit tens of extra optical signals. Therefore, there is a problem that large waste occurs in power consumption.

An object of the present invention is to provide a semiconductor laser output control device and an optical signal transmission system capable of appropriately controlling laser light to be injected into an optical amplifier according to the number of channels of an optical signal. .

[0010]

According to the first aspect of the present invention, there is provided (a) monitoring means for monitoring laser light output from a semiconductor laser for injecting pumping light of an optical direct amplifier;
(B) current variable control means connected in parallel with the semiconductor laser; and (c) current adjustment means connected in series with a parallel circuit composed of the semiconductor laser and the current variable control means for adjusting the current flowing therethrough. And (d) controlling the current variable control means in accordance with the output of the semiconductor laser monitored by the monitor means to control the laser light output from the semiconductor laser to be constant under the condition that a constant current flows through the parallel circuit. The semiconductor laser output control device includes: an output control means; and (e) a current control means for controlling a current flowing through the parallel circuit by controlling the current adjustment means in accordance with the number of channels of the optical signal amplified by the optical direct amplifier. Let it.

That is, according to the first aspect of the present invention, the monitoring means and the current variable control means for compensating the output of the semiconductor laser for injecting the pumping light of the optical direct amplifier against the fluctuation of the input voltage and the ambient temperature are provided. On the other hand, the current adjusting means is controlled in accordance with the number of channels of the optical signal amplified by the optical direct amplifier to control the current flowing in the parallel circuit. I try to change the rate. As a result, it is possible to freely change the number of optical signal channels while ensuring stability against fluctuations in the input voltage and the ambient temperature, and it is not necessary to prepare dummy channels. As a result, the power consumption required for a system using the semiconductor laser output control device can be reduced.

According to the second aspect of the present invention, (a) an optical direct amplifier for directly amplifying an optical signal, (b) a semiconductor laser for injecting pump light into the optical direct amplifier, and (c) for the same transmission line The optical signal transmission system includes: a channel number input unit for inputting the number of channels of the optical signal; and (d) a semiconductor laser driving unit for changing an output of the semiconductor laser in accordance with the number of channels input by the channel number input unit. Let it.

That is, according to the present invention, a channel number input means for inputting the number of optical signal channels for the same transmission line is provided so that the number of optical signal channels used for the same transmission line varies. The output of the semiconductor laser is changed accordingly. As a result, the number of optical signal channels can be freely changed, and there is no need to prepare dummy channels. As a result, power consumption required for the optical signal transmission system can be reduced.

According to the third aspect of the present invention, (a) an optical direct amplifier for directly amplifying an optical signal, (b) a semiconductor laser for injecting pump light into the optical direct amplifier, and (c) an optical transmission line for the same transmission line The optical signal transmission system includes: a channel number detecting unit that detects the number of channels of the optical signal; and (d) a semiconductor laser driving unit that changes the output of the semiconductor laser according to the number of channels detected by the channel number detecting unit. Let it.

That is, in the third aspect of the invention, unlike the second aspect of the invention, a channel number detecting means for detecting the number of optical signal channels for the same transmission line is provided instead of inputting the number of channels. ing. As a result, the number of optical signal channels can be freely changed, and there is no need to prepare dummy channels.
As a result, power consumption required for the optical signal transmission system can be reduced. Further, even if the number of channels fluctuates, the output of the semiconductor laser can be quickly controlled without manual intervention.

According to the fourth aspect of the present invention, (a) an optical direct amplifier for directly amplifying an optical signal, (b) a semiconductor laser for injecting pump light into the optical direct amplifier, and (c) an output from the semiconductor laser Monitoring means for monitoring the laser light to be applied; (d) current variable control means connected in parallel with the semiconductor laser; (e) serially connected to a parallel circuit composed of the semiconductor laser and the current variable control means; Current adjusting means for adjusting the current flowing therethrough, and controlling the current variable control means in accordance with the output of the semiconductor laser monitored by the monitor means to control the current from the semiconductor laser under the condition that a constant current flows through the parallel circuit. Automatic output control means for controlling the output laser light to be constant; and (g) controlling the current adjusting means in accordance with the number of channels of the optical signal amplified by the optical direct amplifier, and It is provided to an optical signal transmission system and a current control means for controlling the.

That is, in the invention described in claim 4, the invention described in claim 1 and the optical signal transmission system described in claim 2 are integrated, and a circuit device for controlling the output of a semiconductor laser is embodied. ing. As a result, the number of optical signal channels can be freely changed, and there is no need to prepare dummy channels. As a result, power consumption required for the optical signal transmission system can be reduced. Further, the system can be improved only by modifying a part of the circuit of the existing semiconductor laser output control device.

According to the fifth aspect of the present invention, (a) an optical direct amplifier for directly amplifying an optical signal, (b) a semiconductor laser for injecting pump light into the optical direct amplifier, and (c) an output from the semiconductor laser Monitoring means for monitoring the laser light to be applied; (d) current variable control means connected in parallel with the semiconductor laser; (e) serially connected to a parallel circuit composed of the semiconductor laser and the current variable control means; Current adjusting means for adjusting the current flowing therethrough, and controlling the current variable control means in accordance with the output of the semiconductor laser monitored by the monitor means to control the current from the semiconductor laser under the condition that a constant current flows through the parallel circuit. Automatic output control means for controlling the output laser light to be constant; (g) channel number input means for inputting the number of optical signal channels for the same transmission line;
(H) A correspondence table indicating the output level of the pumping light of the semiconductor laser for realizing the amplification factor of the optical direct amplifier corresponding to the number of channels input by the number of channels input means, corresponding to the number of channels, is stored. The correspondence table storage means and (i) controlling the current adjustment means in accordance with the number of channels of the optical signal input by the channel number input means based on the correspondence table stored in the correspondence table storage means, thereby forming a parallel circuit. Current control means for controlling the flowing current is provided in the optical signal transmission system.

That is, in the fifth aspect of the present invention, the fourth aspect of the present invention is embodied as a channel number input means and a means related thereto.

According to the present invention, (a) an optical direct amplifier for directly amplifying an optical signal, (b) a semiconductor laser for injecting pump light into the optical direct amplifier, and (c) an output from the semiconductor laser Monitoring means for monitoring the laser light to be applied; (d) current variable control means connected in parallel with the semiconductor laser; (e) serially connected to a parallel circuit composed of the semiconductor laser and the current variable control means; Current adjusting means for adjusting the current flowing therethrough, and controlling the current variable control means in accordance with the output of the semiconductor laser monitored by the monitor means to control the current from the semiconductor laser under the condition that a constant current flows through the parallel circuit. Automatic output control means for controlling the output laser light constant; (g) channel number detection means for detecting the number of optical signal channels for the same transmission line;
(H) A correspondence table indicating the output level of the pumping light of the semiconductor laser for realizing the amplification factor of the optical direct amplifier corresponding to the number of channels detected by the number-of-channels detecting means, corresponding to the number of channels, is stored. The correspondence table storage means and (i) controlling the current adjusting means in accordance with the number of optical signal channels for the same transmission path detected by the channel number detection means based on the correspondence table stored in the correspondence table storage means. And a current control means for controlling a current flowing through the parallel circuit.

That is, in the sixth aspect of the present invention, the fourth aspect of the present invention is embodied as channel number detecting means and means relating thereto.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to embodiments.

FIG. 1 shows an optical signal transmission system using a semiconductor laser output control device according to an embodiment of the present invention. In this optical signal transmission system, an upstream optical fiber transmission line 203 in which a first transmitter 201 and a first receiver 202 are arranged at both ends, a second transmitter 205 and a second receiver 206 are provided. And a downstream optical fiber transmission line 207 disposed at both ends.

The first optical signal 211 is transmitted to the first transmitter 20
1 to the upstream optical fiber transmission line 203,
Is directly amplified by the backward pumping method by the Erbium-doped fiber (EDF) 212 of FIG. Downstream of the first erbium-doped fiber 212, a first WDM (wavelength division multiplexing) coupler 213 for injecting a laser beam for pumping at the time of backward pumping is arranged. First W
Further downstream of the DM coupler 213, the first receiver 2 is connected via a first isolator 214 for preventing return reflection.
02 is arranged. The first pump light output unit 216 is connected to the first WDM coupler 213.

On the other hand, the second optical signal 221 is sent from the second transmitter 205 to the downstream optical fiber transmission line 207, and is directly amplified by the second erbium-doped fiber 222 by the backward pumping method. Downstream of the second erbium-doped fiber 222, a second WDM coupler 223 for injecting pumping light at the time of backward pumping is arranged. Further downstream of the second WDM coupler 223, a second isolator 224 for preventing return reflection is provided.
, A second receiver 206 is arranged. The second pump light output unit 226 is connected to the second WDM coupler 223.

FIG. 2 shows a specific circuit configuration of the first pumping light output section. First excitation light output unit 21
6, a zener diode 234 for setting a constant voltage between the two terminals 231 and 232, a series circuit including a monitoring photodiode 235 and a resistor 236 connected in parallel with the zener diode 234;
Similarly, the resistor 237, the semiconductor laser 238 and the first transistor 2 are connected in parallel with the Zener diode 234.
A parallel circuit in which 39 collector-emitters are connected in parallel,
And a second transistor 241 _first collector - and the respective emitter and resistor 242 and a series circuit connected in series. Monitor photodiode 235
Is connected to the input side of the first APC circuit (automatic output control circuit) 243, and the output side of the first APC circuit 243 is connected to the base of the first transistor 239. Have been. The second transistor 241 ₁ of the base, the drive control circuit 245
Is connected.

Since the second pumping light output section 226 is constituted by substantially the same circuit as the first pumping light output section 216, its illustration is omitted. However, in the second pumping light output unit 226, the first pumping light output unit 21 shown in FIG.
The second transistor 241 ₁ in 6 to be replaced with the second transistor 241 _2. A common drive control circuit 245 is used for the first pumping light output unit 216 and the second pumping light output unit 226.

FIG. 3 shows the configuration of this drive control circuit. The drive control circuit 245 has a CPU (Central Processing Unit) 261 mounted thereon. The CPU 261 is connected to a ROM (read only memory) 263, a RAM (random access memory) 264, an input circuit 265, a display control circuit 266, and first and second D / A via a bus 262 such as a data bus. (Digital / Analog)
It is connected to converters 267 and 268. The ROM 263 stores a program for performing the control operation of the drive control circuit 245, and also stores a ROM table 269 in a predetermined area. This RO
The M table 269 is for determining a second transistor 241 _and fourth transistor 241 _{and second} base current with respect to the number of channels set (number of wavelengths). This will be described later in detail.

The RAM 264 is a memory for storing primary data when performing various controls. The input circuit 265 is connected to the input key 271. The input key 271 is for inputting the number of channels of the optical signal transmitted through the upstream optical fiber transmission line 203 or the downstream optical fiber transmission line 207 in the case of the present embodiment. It may be used also for input of other data. Display control circuit 2
Reference numeral 66 denotes a circuit for performing control for displaying predetermined information such as numerical values input to a display 272 such as a liquid crystal display. The first D / A converter 267 is connected to the second transistor 2
The determined digital value for 41 ₁ of the base current is a circuit for applying thereto into an analog value. The second D / A converter 268 is connected to the other second
The transistor 241 digital values determined for the _second base current is a circuit for applying thereto into an analog value.

FIG. 4 shows the flow of processing when the number of wavelengths is changed using the drive control circuit of the semiconductor laser output control device configured as described above. When the drive control circuit 245 determines that the wavelength number change mode has been set by operating the input key 271 shown in FIG. 3 (step S301: Y), the drive control circuit 245 responds to the number of channels to be used, which will be described next. Corresponding optical fiber transmission line 203
Alternatively, the control of the excitation light 207 is performed. In other cases (step S301: N), a standby state for executing another mode or executing one of the modes is set.

When the mode is set to the wavelength number change mode,
The operator instructs the display 272 shown in FIG. 3 to display an inquiry as to which of the upstream optical fiber transmission line 203 and the downstream optical fiber transmission line 207 is to control the output of the laser light. It waits for the user to select either up or down (step S30).
2, S303). When the operator operates the upstream optical fiber transmission line 20
If 3 is selected (step S302: Y), input of the number of channels of the optical signal after the change is awaited subsequently (step S304). When the number of optical signal channels for the same transmission path is input (Y), the CP shown in FIG.
U261 determines the second transistor 241 ₁ of the base current with the ROM table 269 (step S3
05).

FIG. 5 shows the contents stored in the ROM table. A channel (ch) of the light signal to the ROM table 269, the value of the second transistor 241 _1, 241 ₂ of the base current corresponding thereto are stored as a data relationship as shown in FIG. Since the second transistor 241 _1, 241 ₂ in this embodiment has almost the same characteristics with each other, the contents of the table are common. In this example, when the number of channels of the optical signal is "8", the base current is 100 milliamps. When the number of optical signal channels increases to "64", the base current increases to 400 milliamps in this example. By increasing or decreasing the base current of the second transistor 241 _1, 241 of the _two corresponding ones, these transistors 241 _1, 241 ₂ of the collector - the resistance value between the emitter is changed. Thereby, the corresponding transmission path 20
3 or 207 can be increased or decreased, and the first erbium-doped fiber 212 or the second erbium-doped fiber 222
Can be changed.

Returning to FIG. 4, the description will be continued. Step S3
After 05 the base current for the second transistor 241 ₁ is determined, the digital value is a first corresponding thereto
Is applied to the D / A converter 267. As a result, the second transistor 24 of the upstream optical fiber transmission line 203
1 ₁ of base current will be set to a value corresponding to the number of channels of the new number of wavelengths that is, the optical signal (step S306).

Thereafter, the CPU 261 determines in step S302
Return to the processing of. At this stage, for example, when the operator selects the down optical fiber transmission line 207 (step S3
03: Y), the CPU 261 determines the ROM table 269 according to the number of input channels (step S307: Y).
Determining a second transistor 241 _{and second} base current with (step S308). Then, the corresponding digital value is applied to the second D / A converter 268. As a result, the downstream optical fiber transmission line 2
Second transistor 241 _{and second} base current of 07 is set to a value corresponding to the number of channels of the new optical signal (step S309).

In contrast to the above, when returning to step S302 or when the operator sets the wavelength number change mode due to an error, an input for terminating the set wavelength number change mode is performed. (Step S3
10), the wavelength number change mode ends (return).

As a result of the above-described control, in the present embodiment, when changing the number of optical signal channels in the upstream optical fiber transmission line 203 or the downstream optical fiber transmission line 207, the operator changes the changed channel number. Only by inputting, the output of the semiconductor laser for pumping can be appropriately controlled.

First Modified Example

FIG. 6 shows an optical signal transmission system using a semiconductor laser output control device according to a first modification of the present invention. In this modification, an optical coupler 401 is arranged on the output side of the first pumping light output unit 216 and the second pumping light output unit 226. And this optical coupler 4
01 mixed laser light 40 of the same wavelength
2, 403 is the first or second WDM (wavelength division multiplexing)
The light is injected into the corresponding first or second erbium-doped fiber 212, 222 via the couplers 213, 223.

As described above, in the first modification, the optical coupler 40
1 is provided to make the output laser light redundant. As a result, when one of the semiconductor lasers 238 (see FIG. 2) as the pumping light source of the first and second pumping light output units 216 and 226 disposed for a long time on the seabed or the like is deteriorated, Even when an error occurs in the constant and the output fluctuates, the direct influence of the output fluctuation can be reduced, and the laser light 40
The reliability of the output level of 2,403 can be improved.

Second Modification

FIG. 7 shows a configuration on the upstream optical fiber transmission line side in an optical signal transmission system using a semiconductor laser output control device according to a second modification of the present invention. In FIG. 7, the same portions as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted as appropriate. Also, the configuration of the downstream optical fiber transmission line is essentially the same, so that its illustration is omitted.

In the second modification, the first transmitter 20
An optical coupler 501 is arranged between the first and the first erbium-doped fibers 212, and an optical signal demultiplexed from the optical coupler 501 is input to a channel number detection unit 502. The channel number detection unit detects the number of channels of the optical signal transmitted through the upstream optical fiber transmission line 203. Such detection of the number of channels can be determined by converting the optical output power of the first transmitter 201 into an electric signal using a photodiode (not shown) and the output level thereof. Of course, when performing highly accurate detection, the number of wavelengths (channels) in which the optical signal exists may be counted by checking the presence or absence of the output through a band-pass filter corresponding to the wavelength of each channel. .

A channel number signal 503 indicating the number of channels detected by the channel number detecting section 502 is input to the first pumping light output section 216A. First excitation light output section 216
A can be configured with basically the same circuit as the first pumping light output unit 216 of the previous embodiment. The difference from the first pumping light output unit 216 of the embodiment is that the input key 271 and the input circuit 265 in FIG. 3 are constituted by, for example, an A / D converter for inputting the output of the photodiode described above. It is a point that is done. In the case of this example, the voltage output from the photodiode is converted into a digital signal in proportion to the number of channels of the optical signal, and is converted into the number of channels by another ROM table (not shown). Of course, it is also possible to input the voltage output from the photodiode or the original data for judging the number of channels into the ROM table and directly obtain the value of the base current of the second transistor 241 ₁ (FIG. 2) therefrom. It is.

Third Modified Example

FIG. 8 shows a configuration on the upstream optical fiber transmission line side in an optical signal transmission system using a semiconductor laser output control device according to a third modification of the present invention. In FIG. 8, the same portions as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted as appropriate. Also, the configuration of the downstream optical fiber transmission line is essentially the same, so that its illustration is omitted.

In the third modification, the first transmitter 20
1 and the first erbium-doped fiber 212
Is arranged so that the laser light is injected from the first pumping light output unit 216 into the first erbium-doped fiber 212 by the forward pumping method. Other points are the same as in the previous embodiment.

In the embodiment described above, the output of the semiconductor laser 238 connected in series to the second transistor 241 ₁ , 241 ₂ is controlled by controlling the base current. It is also within the scope of the present invention to control the output level according to the number of channels by another conventional method of changing the output of the H.238.

[0049]

As described above, according to the first aspect of the present invention, the output of the semiconductor laser for injecting the pumping light of the optical direct amplifier is compensated for the fluctuation of the input voltage and the ambient temperature. Since the monitoring means and the variable current control means are used, the current flowing through the parallel circuit is controlled by controlling the current adjustment means according to the number of channels of the optical signal amplified by the optical direct amplifier. It is possible to freely change the number of optical signal channels while ensuring stability against fluctuations in ambient temperature and ambient temperature, and it is not necessary to prepare dummy channels. As a result, not only can the power consumption required for the system using the semiconductor laser output control device be reduced effectively,
No circuitry is required to create and process dummy optical signals.

According to the second aspect of the present invention, there is provided a channel number input means for inputting the number of optical signal channels for the same transmission line so that the number of optical signal channels used for the same transmission line varies. In this case, the output of the semiconductor laser is changed accordingly, so that the number of optical signal channels can be changed freely, and it is not necessary to prepare dummy channels. As a result, not only can the power consumption required for the optical signal transmission system be reduced, but also a circuit for creating and processing a dummy optical signal is not required. Further, by setting the number of channels intentionally to a different value, it is possible to compensate for the deterioration and the difference in characteristics of the semiconductor laser.

Further, according to the third aspect of the present invention, a channel number input means for inputting the number of optical signal channels for the same transmission line is provided so that the number of optical signal channels used for the same transmission line varies. In this case, the output of the semiconductor laser is changed accordingly, so that the number of optical signal channels can be changed freely, and it is not necessary to prepare dummy channels. As a result, not only can the power consumption required for the optical signal transmission system be reduced, but also a circuit for creating and processing a dummy optical signal is not required. Further, even if the number of channels fluctuates, the output of the semiconductor laser can be quickly controlled without manual intervention.

According to the present invention, the system can be improved by merely modifying a part of the circuit of the existing circuit device for controlling the output of the semiconductor laser, and the system can be improved. Cost increase can be avoided.

Further, according to the fifth aspect of the invention, the amplification factor of the amplifier can be adjusted by intentionally setting the number of channels to a different value. Can compensate.

According to the invention of claim 6, since it is not necessary to input the number of channels, it is possible to avoid human error and to cope with frequent changes in the number of channels. be able to.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram showing an optical signal transmission system using a semiconductor laser output control device according to an embodiment of the present invention.

FIG. 2 is a circuit diagram illustrating a specific circuit configuration of a first pumping light output section of the present embodiment.

FIG. 3 is a block diagram illustrating a configuration of a drive control circuit according to the present embodiment.

FIG. 4 is a flowchart showing the flow of processing when the number of wavelengths is changed using the drive control circuit of the semiconductor laser output control device of the present embodiment.

FIG. 5 is an explanatory diagram showing stored contents of a ROM table according to the present embodiment.

FIG. 6 is a system configuration diagram showing an optical signal transmission system using a semiconductor laser output control device according to a first modification of the present invention.

FIG. 7 is a system configuration diagram showing a configuration on an upstream optical fiber transmission line side in an optical signal transmission system using a semiconductor laser output control device according to a second modification of the present invention.

FIG. 8 is a system configuration diagram showing a configuration on an upstream optical fiber transmission line side in an optical signal transmission system using a semiconductor laser output control device according to a third modification of the present invention.

FIG. 9 is a circuit diagram showing an outline of a circuit configuration of a conventionally used semiconductor laser output control device.

[Explanation of symbols]

 201 first transmitter 202 first receiver 203 upstream optical fiber transmission line 205 second transmitter 206 second receiver 207 downstream optical fiber transmission line 212 first erbium-doped fiber 213 first WDM (Wavelength division multiplexing) Coupler 216, 216A First pumping light output section 222 Second erbium-doped fiber 223 Second WDM coupler 226 Second pumping light output section 238 Semiconductor laser 241 Second transistor 245 Drive control circuit 261 CPU (Central Processing Unit) 263 ROM 267 First D / A converter 268 Second D / A converter 269 ROM table 271 Input keys 401, 501 Optical coupler 502 Channel number detector

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04B 10/04 H04B 9/00 E 10/17 10/16 H04J 14/00 14/02

Claims (6)

[Claims] 1. A monitoring means for monitoring laser light output from a semiconductor laser for pumping light injection of an optical direct amplifier, a current variable control means connected in parallel with the semiconductor laser, and a current variable with the semiconductor laser. A current adjusting unit that is connected in series with a parallel circuit configured by a control unit and adjusts a current flowing therethrough; and controls the current variable control unit according to an output of the semiconductor laser monitored by the monitoring unit. Automatic output control means for controlling the laser light output from the semiconductor laser to a constant value under the condition that a constant current flows through the parallel circuit; and the current according to the number of channels of the optical signal amplified by the optical direct amplifier. A current control means for controlling a current flowing through the parallel circuit by controlling an adjusting means. 2. An optical direct amplifier for directly amplifying an optical signal, a semiconductor laser for injecting pump light into the optical direct amplifier, and a channel number input means for inputting the number of channels of the optical signal to the same transmission line; An optical signal transmission system comprising: a semiconductor laser driving unit that changes an output of the semiconductor laser according to the number of channels input by the channel number input unit. 3. An optical direct amplifier for directly amplifying an optical signal; a semiconductor laser for injecting pump light into the optical direct amplifier; a channel number detecting means for detecting the number of channels of the optical signal with respect to the same transmission line; An optical signal transmission system comprising: a semiconductor laser driving unit that changes an output of the semiconductor laser according to the number of channels detected by the channel number detecting unit. 4. An optical direct amplifier for directly amplifying an optical signal, a semiconductor laser for injecting pump light into the optical direct amplifier, monitoring means for monitoring laser light output from the semiconductor laser, Current variable control means connected in parallel; a current adjusting means connected in series with a parallel circuit comprising the semiconductor laser and the current variable control means for adjusting a current flowing therethrough; and An automatic output control unit that controls the current variable control unit in accordance with the output of the semiconductor laser and controls the laser light output from the semiconductor laser to be constant under a condition that a constant current flows through the parallel circuit; A current control means for controlling the current adjusting means in accordance with the number of channels of the optical signal amplified by the optical direct amplifier to control the current flowing through the parallel circuit; An optical signal transmission system comprising: 5. An optical direct amplifier for directly amplifying an optical signal, a semiconductor laser for injecting pump light into the optical direct amplifier, monitoring means for monitoring laser light output from the semiconductor laser, and the semiconductor laser. Current variable control means connected in parallel; a current adjusting means connected in series with a parallel circuit comprising the semiconductor laser and the current variable control means for adjusting a current flowing therethrough; and The same as the automatic output control means for controlling the current variable control means in accordance with the output of the semiconductor laser to control the laser light output from the semiconductor laser constant under the condition that a constant current flows in the parallel circuit; Channel number input means for inputting the number of channels of the optical signal with respect to the transmission path, and channels input by the channel number input means Correspondence table storing means for storing a correspondence table indicating the output level of the pumping light of the semiconductor laser for realizing the amplification factor of the optical direct amplifier corresponding to the number of channels, the correspondence table storing means Current control means for controlling the current adjusting means according to the number of channels of the optical signal input by the channel number input means based on the stored correspondence table to control the current flowing in the parallel circuit. An optical signal transmission system, comprising: 6. An optical direct amplifier for directly amplifying an optical signal, a semiconductor laser for injecting pump light into the optical direct amplifier, monitoring means for monitoring laser light output from the semiconductor laser, Current variable control means connected in parallel; a current adjusting means connected in series with a parallel circuit comprising the semiconductor laser and the current variable control means for adjusting a current flowing therethrough; and The same as the automatic output control means for controlling the current variable control means in accordance with the output of the semiconductor laser to control the laser light output from the semiconductor laser constant under the condition that a constant current flows in the parallel circuit; Channel number detecting means for detecting the number of channels of the optical signal with respect to the transmission path, and channels detected by the channel number detecting means. Correspondence table storing means for storing a correspondence table indicating the output level of the pumping light of the semiconductor laser for realizing the amplification factor of the optical direct amplifier corresponding to the number of channels, the correspondence table storing means Current control for controlling the current adjusting means in accordance with the number of channels of the optical signal for the same transmission path detected by the channel number detecting means based on the stored correspondence table to control the current flowing in the parallel circuit; And an optical signal transmission system.