JP2546499B2 - Optical signal direct amplifier - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical signal direct amplifier for directly amplifying an optical signal as it is, and more specifically, to stop or reduce the output power when the optical connector on the output side is disconnected. The present invention relates to an optical signal direct amplifier.

[0002]

2. Description of the Related Art A high output optical signal is output from an optical transmitter. It is dangerous for such a high-power optical signal to be seen by a person performing maintenance or management work. For this reason, there has been conventionally known an optical amplifying device which detects an accident that an output connector of a high output optical amplifier is disconnected by an increase in the reflection amount of an optical signal and automatically stops or reduces the output power.

FIG. 2 shows a circuit configuration of such a conventional optical amplifier device. An optical signal input from the input optical connector 11 of this device is input to a wavelength division multiplexer (WDM) 12. The pumping light from the pumping light source 13 is also input to the wavelength division multiplexing coupler 12, and the two are combined to form an erbium-doped fiber (Erbium Doped Fiber).
Fiber) 14 is input.

The erbium-doped fiber 14 is an amplifier that directly amplifies the input light, and the amplified optical signal passes through a first optical directional coupler 15 and a second optical directional coupler 16 and an optical output connector 17 is provided. Is output to. here,
The first optical directional coupler 15 branches a part of the input optical signal and inputs it into the first light receiving element 18. The output of the first light receiving element 18 is an automatic power control (APC;
Control) circuit 19 is input. The output of the automatic power control circuit 19 is input to the laser drive circuit 21, which causes the laser drive circuit 21 to apply a current to the excitation light source 13 so that the output of the first light receiving element 18 becomes constant. Will be adjusted.

On the other hand, the second optical directional coupler 16 splits the reflected return light and inputs it into the second light receiving element 23. In general, a part of the optical signal output from the optical output connector 17 is reflected from the end face of the optical output connector 17 or the transmission path and returns to the amplifier side again. If the optical output connector 17 comes off, the amount of reflected return light increases. The second optical directional coupler 16 will detect this reflected return light. The output of the second optical directional coupler 16 is input to the determination circuit 24, where the output optical connector disconnection is determined. When the determination circuit 24 determines that the output optical connector is disconnected, a signal for stopping the current application to the laser drive circuit 21 is generated. Based on this, the laser drive circuit 21 changes the current applied to the excitation light source 13 to “0” amperes, and stops the output of the excitation light.

On the other hand, FIG.
10 shows an optical output control circuit of the optical connector connection type device disclosed in Japanese Patent Laid-Open No. In this circuit, the output connector 32 to which the optical fiber 31 is connected is the receptacle 33.
The output of the laser diode 36 in the automatic output control circuit 35 is detected by the optical output control unit 34 when it is out of the range.

That is, in the automatic output control circuit 35 of this optical output control circuit, the input signal 37 is added to the output of the bias circuit 39 by the adder 38 and given to the laser diode 36,
It is designed to control the light emission, and the photodiode 41
Then, a part of it is detected and amplified by the amplifier 42, and the reference voltage 4
A feedback loop is configured so that 3 is input to the other end of the differential amplifier 44.

On the other hand, a sensor light emitter 46 and a sensor light receiver 47 are arranged in the vicinity of the output connector 32, and when the output connector 32 is disengaged from the receptacle 33, the light reflected by the outer periphery of the output connector 32 is detected by the sensor light receiver. The amount of light incident on 47 is reduced. The output of the sensor light receiver 47 is amplified by an amplifier 48, and a comparator 49
It is input to one input terminal and compared with the threshold voltage 51 applied to the other input terminal. Then, when the amount of light incident on the sensor light receiver 47 decreases the threshold value, it is determined that the output connector 32 is disconnected, and the output level of the comparator 49 is changed to change the potential on the reference voltage 43 side to change the potential of the laser diode 36. It is designed to reduce the output.

In Japanese Utility Model Application No. 62-20003 (Japanese Utility Model Application Laid-Open No. 63-127655), a treatment area exists by irradiating a light beam in the vicinity of the laser light irradiation area and detecting the reflected light. There is disclosed a technique in which it is determined whether or not a treatment site does not exist and irradiation with laser light is not performed.

Japanese Patent Publication No. 58-14218 discloses that
Disclosed is a probe detachment detection device which generates an alarm when a probe that comes into contact with a human body is detached. In this probe detachment detection device, a light receiving means is arranged on the human body contact surface side of the probe, and when the probe detaches, ambient light is detected to make the determination, and an alarm is generated. .

[0011]

By the way, as described above, when the connector disconnection occurs on the output side of the optical signal direct amplifier, the reflection at the end face of the optical output connector increases, and the conventional optical signal shown in FIG. In the direct amplifier, the determination circuit 24 detects the increase of the reflected return light laser and stops the output of the pumping light from the pumping light source 13. After this, the reflected return light disappears, so that the connector is apparently mounted normally. Then, the alarm warning that the connector is disconnected will be canceled.

Therefore, in the conventional optical signal direct amplifier shown in FIG. 2, once the connector disconnection is detected, the drive of the pumping light source 13 is stopped and this state is maintained. As a result, the warning associated with the driving stop of the excitation light source 13 is released, or the excitation light source 1 is released with the connector disconnected.
3 is prevented from being restarted. However, in this optical signal direct amplifier shown in FIG. 2, since the pumping light source itself is stopped, the reflected return light cannot be detected, and the connector is normally operated after the alarm is issued. Even if it is attached, this cannot be detected by the circuit.
Therefore, when recovery is performed after the alarm is issued, it is necessary to manually release the alarm and restart the optical signal direct amplifier.

Further, in the conventional optical output control circuit shown in FIG. 3, the output of the laser diode 36 is controlled by utilizing the reflected light on the outer periphery of the output connector 32, so that some kind of reflection object is detected by the sensor light emitter 46. If it is brought closer to the sensor light receiver 47 or the sensor light receiver 47, the output level of the laser diode 36 will erroneously return to a normal value, which is dangerous.

Therefore, an object of the present invention is to basically use the conventional optical signal direct amplifier as shown in FIG. 2 to detect the disconnection of the connector and to automatically restart after the recovery. To provide.

[0015]

In [Summary of] claim 1 the described invention, the erbium-doped Fiber <br/> server as amplification medium of the optical signal, an excitation light source for sending a pumping light to the erbium-doped fiber, the excitation a laser drive circuit for driving the light source, a wavelength division multiplexing coupler for multiplexing the pump light and optical signal to be inputted to the erbium-doped fiber, an erbium dough
A first optical splitter for splitting part of the optical signal sent from the pull fiber to the output side of the optical connector, a first light receiving element for detecting the optical signal branched by the first optical branching unit, an output The second light receiving element that detects the reflected return light from the optical connector on the side and the output of the second light receiving element
If it is damaged, it will be much larger than the detection output of the first light receiving element.
Level adjustment that amplifies to a predetermined level
Circuit, the output of the first light receiving element and the output of the level adjustment circuit
The optical signal direct amplifier is provided with an adder for adding and, and an automatic power control circuit for controlling the laser drive circuit so that the output of the adder becomes a predetermined value.

That is, in the invention according to claim 1, the reflected return light from the optical connector on the output side is received by the second light receiving element.
Then, the output is output from the second light receiving element by the level adjustment circuit.
Is the detection output of the first light receiving element when the optical connector is disconnected.
To a predetermined level that is sufficiently large.
Amplify with the level adjustment circuit at
Part of the optical signal output from the erbium-doped fiber
The output after photoelectric conversion of is added by an adder. This addition
The output of the calculator is the automatic power that controls the level drive circuit.
It will be used as an input signal of the control circuit. That
If the connector comes off, the reflected return light increases.
By increasing the input signal of the automatic power control circuit
Low enough optical signal output from rubium-doped fiber
I am trying to let you down. Further, when the connector is properly attached, the input signal of the automatic power control circuit falls to the normal range, thereby enabling automatic restart after restoration.

[0017]

[0018]

[0019]

[0020]

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

FIG. 1 shows the configuration of an optical signal direct amplifier according to an embodiment of the present invention. The same parts as those in FIG. 2 are designated by the same reference numerals. In the optical signal direct amplifier of the present embodiment, the output signal output from the second light receiving element 23 is input to the level adjusting circuit 61, the level thereof is adjusted, and then input to the adder 62. Adder 6
The output signal of the first light receiving element 18 is also input to 2, and the two are added. The output of the adder 62 is input to the automatic power control circuit 19. The control of the laser drive circuit 21 by this is the same as that of the optical signal direct amplifier shown in FIG.

The operation of the optical signal direct amplifier having such a configuration will be described. The optical signal input from the input optical connector 11 is combined with the pumping light output from the pumping light source 13 by the wavelength division multiplexing coupler 12, and the erbium-doped fiber 14
After being amplified by, the light is output from the optical output connector 17.
A part of the optical signal amplified by the erbium-doped fiber 14 is branched by the first optical directional coupler 15 and received by the first light receiving element 18. In addition, the reflected return light reflected by the optical output connector 17 is the second optical directional coupler 1.
It passes through 6 and enters the second light receiving element 23.

First, the case where the optical output connector 17 is properly mounted will be described. In this case, the output of the second light receiving element 23 is 40d greater than the output of the first light receiving element 18.
It is also lower than B. Therefore, the output of the adder 62 becomes equal to the output of the first light receiving element 18. Automatic power control circuit 1
9 controls the laser drive circuit 21 so that the output of the first light receiving element 18 is always constant, and in this situation, the output light level of this optical signal direct amplifier is kept constant. Become.

Next, the case where the optical output connector 17 is disconnected will be described. When disconnection of the optical output connector occurs, the reflected return optical power input to the second light receiving element 23 increases several hundred times as compared with the case where the connector is properly mounted. As a result, the output of the second light receiving element 23 also increases several hundred times.
This output is amplified by the level adjusting circuit 61 and added by the adder 62.
Is input to The output of the adder 62 is the first light receiving element 18
And the output of the level adjusting circuit 61. As a result, the automatic power control circuit 19 apparently determines that the output light level of the erbium-doped fiber 14 has increased, and controls the laser drive circuit 21 to reduce the output light level of the pumping light source 13.

By the way, the amplification degree of the level adjusting circuit 61 is set so that the output level of the erbium-doped fiber 14 is weakened so that the human body is not affected when it is assumed that total reflection occurs at the optical output connector 17. Therefore, even when the optical output connector is disconnected, the optical signal is output from the erbium-doped fiber 14 at a level that does not affect the human body, and the reflected return light due to the optical output connector disconnection does not become zero. Therefore, while the optical output connector 17 is disconnected, it is possible to always detect the optical output connector disconnection.

When the optical output connector 17 is mounted again after the disconnection of the optical output connector, the reflected return light level is greatly reduced as before. As a result, the adder 62
Again becomes approximately equal to the output level of the first light receiving element 18. As a result, the automatic power control circuit 19 restores the output light level of the pumping light source 13 and the output light level of the erbium-doped fiber 14 returns to the normal output level.

In the embodiment, the erbium-doped fiber is used for the optical signal direct amplifier, but other rare earth-doped fiber can be used. Further, in the embodiment, the output of the second light receiving element 23 is set to the level adjusting circuit 6
Although the output of the first light receiving element 18 is added to the output of the first light receiving element 18 after adjustment by 1, the arithmetic circuit for adding the outputs of both the light receiving elements 18 and 23 at a predetermined ratio is provided, and the level adjusting circuit 61 is omitted. It is also possible to do so.

[0028]

As described above , according to the first aspect of the present invention, the level of the optical signal output from the erbium-doped fiber is not reduced to zero even when the optical output connector is disconnected. The connector detached state can be held without requiring a special holding circuit. Moreover, the optical connector outputs the output of the second light receiving element.
Larger than the detection output of the first light receiving element when it comes off
Level adjustment times up to a predetermined level
I decided to amplify it on the optical path, so in this state the level of the optical signal
To ensure safety by making the size sufficiently small.
Can be. Moreover, when the connector disconnection is restored, the output level of the optical signal automatically returns to the normal state, so that the efficiency of maintenance and the like can be improved. Further, according to the present invention, since an optical signal direct amplifier which can completely cope with connector disconnection can be made without making any change to the existing optical signal direct amplifier, an economical optical communication system is constructed. can do.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an optical signal direct amplifier according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a circuit configuration of a conventionally proposed optical amplifier.

FIG. 3 is a block diagram showing an optical output control circuit of a conventionally proposed optical connector connection type device.

[Explanation of symbols]

11 Input Optical Connector 12 Wavelength Division Multiplexer 13 Excitation Light Source 14 Erbium Doped Fiber (Rare Earth Doped Fiber) 15 First Optical Directional Coupler 16 Second Optical Directional Coupler 17 Optical Output Connector 18 First Photosensitive Element 19 Automatic power control circuit 21 Laser drive circuit 23 Second light receiving element 61 Level adjusting circuit 62 Adder

Claims (1)

(57) [Claims] 1. An erbium oxide as an optical signal amplification medium.
And-loop fiber, an excitation light source for sending a pumping light to the erbium-doped fiber, a laser drive circuit for driving the excitation light source, a wavelength division multiplexing for multiplexing optical signals for input to the erbium-doped fiber and the pumping light A coupler; a first optical branching device for branching a part of the optical signal sent from the erbium-doped fiber to the output-side optical connector; and a first optical branching device for detecting the optical signal branched by the first optical branching device. a light receiving element, when a second light receiving element for detecting light reflected back from the optical connector of the output side, the optical connector the output of the second light receiving element is out
Is sufficiently larger than the detection output of the first light receiving element
Level adjustment times to amplify to a predetermined level such as
Path, add the output of the first light receiving element and the output of the level adjustment circuit
And an automatic power control circuit for controlling the laser drive circuit so that the output of the adder has a predetermined value.