JP3018772B2 - Optical 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 amplifier, and more particularly to an optical amplifier having a monitoring function.

[0002]

2. Description of the Related Art Recently, an optical amplifier for directly amplifying an optical signal is used as an optical amplifier for amplifying an optical signal in optical communication.
Among these optical amplifiers, the one used to amplify (approximately 20 dB) high input light (about 0 dBm) and obtain high output is called a post amplifier. Generally, in a post-amplifier, input light, output light, and reflected return light (reflected light) from an output terminal are monitored in order to control the operation. The monitoring of the input light detects the non-input state to the optical amplifier and stops the operation of the optical amplifier, the monitoring of the output light controls the output from the optical amplifier to a constant level, and the monitoring of the reflected light uses the light. This is performed to stop the operation of the optical amplifier by detecting disconnection of the connector at the output end of the amplifier or disconnection behind the optical amplifier. That is, the normal operation of the optical amplifier is controlled by monitoring the output light, and the monitoring of the input light and the reflected light only detects the state where the optical amplifier should be stopped.

Conventionally, an optical amplifier having such a monitoring function has a configuration shown in FIG. Hereinafter, the operation will be described with reference to FIG. The input-side optical splitter 31 inserted in front of the optical amplifier 22 is a three-port fused optical coupler, and 90% of the light incident from the input terminal 27 is input to the optical amplifier 22.
10% is emitted to the light receiving module 24.

The optical splitter 33 on the output side of the optical amplifier 22 has four
90% of the light incident from the optical amplifier 22 is output to the output terminal 28 by the fused optical coupler of the port and 10% to the light receiving module 2
6, and 90% of the light incident from the output terminal 28 is emitted to the optical amplifier 22 side and 10% to the light receiving module 25. Therefore, 90% of the output light from the optical amplifier 22 is output, and 10% is incident on the light receiving module 26 and monitored. Similarly, 10% of the reflected light enters the light receiving module 25 and is monitored.

[0005]

As described above, the conventional optical amplifier monitors input light, output light, and reflected light.
One light receiving module was used for each. Therefore, three light receiving modules are required, and there are problems in mounting and cost.

[0006]

According to the present invention, there is provided an optical amplifier comprising:
Having at least two ports 1 to 4, the light incident on port 1 is branched into ports 3 and 4, the light incident on port 2 is emitted on port 4, and the light incident on port 4 is transmitted on port 2
A first optical splitter that emits light to the first port and a second optical port that has ports 1 to 4 and that splits at least light incident on port 1 into ports 3 and 4 and emits light incident on port 3 to port 2
An optical amplifier body having an input connected to port 3 of the first optical splitter and an output connected to port 1 of the second optical splitter, and a port of the second optical splitter 3 and the second
A wiring for connecting to port 4 of the first optical branching device;
A first light receiving module having an input connected to port 2 of the optical splitter, a second light receiving module having an input connected to port 4 of the second optical splitter, and the first light receiving module. It has an input terminal connected to the port 1 of the splitter for receiving an optical input signal, and an output terminal connected to the port 2 of the first optical splitter for transmitting an amplified optical output signal.

In particular, the first light receiving module monitors the light input signal and the reflected light of the light output signal, and the second light receiving module monitors the light output signal.

[0008]

Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of an optical amplifier according to this embodiment. In FIG. 1, the loss of the optical branch 6 on the input side is LIT in the straight direction (eg, port 1 to port 2), the LIR in the reflection direction (eg, port 1 to port 4), and the loss of the output branch is straight. , LOT in the reflection direction, and G in the optical amplifier.

The input light that has entered from the input terminal 5 with power P [dBm] enters the port 1 of the optical branch 6 on the input side,
Port 3 emits P-LIT [dBm], and port 4 emits P-LIR [dBm]. The light emitted from the port 4 is incident on the port 3 of the optical branch 7 on the output side, and (P-LIR) -LOR [dBm] is emitted from the port 2. The light emitted from the port 2 enters the light receiving module 8 and is monitored. This is the monitoring of the input light, and monitors MI = P-LIR-LOR [dBm].

The light emitted from the port 3 of the optical splitter 6 is amplified by the optical amplifier 9 (P-LIT) + G [dB].
m]. This is incident on the port 1 of the optical branch 7, (P-LIT + G) -LOT is emitted from the port 3, and (P-LIT + G) -LOR [dBm] is emitted from the port 4. The light emitted from the port 3 of the optical branching device 7 enters the port 4 of the optical branching device 6, and from this port 2 (P-L
(IT + G-LOT) -LIT [dBm] is emitted.
This is emitted from the output terminal 10 and the output light P0 = P + G
-2 LIR-LOT [dBm].

The light emitted from the port 4 of the optical splitter 7 enters the light receiving module 11 and is monitored. This is the monitoring of the output light, and M0 = P-LIT + G-LOR =
Monitor P0-LIT-LOT + LOR [dBm].

The output light having the power P0 [dBm] is reflected at the output terminal 10 with the return loss R, and the power P0-R
The reflected light is [dBm]. This reflected light is transmitted to the optical splitter 6.
From port 2 and from port 4 (P0-R) -L
IT [dBm] is emitted. The light emitted from the port 4 enters the port 3 of the optical branch 7, and (P0-R-LIT) -LOR [dBm] is emitted from the port 2. The light emitted from the port 2 enters the light receiving module 8 and is monitored. This is the monitoring of reflected light,
MR = P0-R-LIT-LOR (= P + GR-3L
IT-LOT-LOR) [dBm] is monitored.

The light receiving module 8 monitors input light and reflected light simultaneously. Since the power MI of light entering the light receiving module 8 as input light and the power MR of light entering the light receiving module 8 as reflected light are obtained, when there is no abnormality at the output end and R is sufficiently large, the reflected light becomes input light. The light receiving module 8 monitors the input light because the reflected light is larger than the input light when an abnormality occurs on the load side of the output terminal 10 and R is small. Then, an abnormality is detected.

Next, the specific configuration and operation of this embodiment will be described. The optical branch 6 is a 4-port fused coupler, and the port 1
90% (LIT = 0.5 dB) of light incident from port 3 is output to port 3 and 10% (LIR = 10 dB) is output to port 4 and 90% of light incident from port 4 is output to port 2.
Emit 0% to port 1. The optical branch 7 on the output side is also a 4-port fused coupler, and 90% of the light incident from the port 1
To port 3 and 10% to port 4, 90% of the light incident from port 3 to port 1 and 10% to port 2.

The light receiving modules 8 and 11 are PD modules. The optical amplifier 9 is a post-amplifier.
It operates with dBm and a gain of 20 dBm. Output terminal 10
Is 40 dB when there is no abnormality, and 15 dB when an abnormality occurs. At this time, the power of the light incident on the light receiving module 8 as the input light is -20 dBm. The power of light incident on the light receiving module 8 as reflected light is -32 dBm when there is no abnormality, and is 12 dB with respect to the input light.
The light receiving module 8 monitors the input light. When an abnormality occurs, it is -7 dBm, which is 13 dB larger than the input light, and the light receiving module 8 monitors the reflected light to detect the occurrence of the abnormality.

The optical branch 6 and the optical branch 7 may be formed by micro optics or a waveguide in addition to the fusion type optical coupler.

The optical branch 6 and the optical branch 7 need not be four ports as long as they have two-input two-output ports or more coupled to each other.

Further, the light receiving modules 8 and 11 are PD
In addition to the module, an APD module may be used.

[0020]

As described above, in the optical amplifier of the present invention, the input light and the reflected light are monitored by one light receiving module, so that the required number of light receiving modules can be reduced by one. This is effective in reducing the size and cost of the optical amplifier.

[Brief description of the drawings]

FIG. 1 is a block diagram of an optical amplifier according to the present invention.

FIG. 2 is a block diagram of a conventional optical amplifier.

[Explanation of symbols]

 5 input terminal 6 optical splitter 7 optical splitter 8 light receiving module 9 optical amplifier 10 output terminal 11 light receiving module

Claims (2)

(57) [Claims] 1. A device having four ports (1) to (4), at least light incident on port (1) is split into ports (3) and (4), light incident on port (2) is emitted on port (4), and light incident on port (4) is output on port (4). A first optical splitter for emitting light to port 2; and a second optical splitter having ports 1 to 4 for splitting at least light incident on port 1 into ports 3 and 4 and emitting light incident on port 3 to port 2. An optical amplifier body having an input connected to port 3 of the first optical splitter and an output connected to port 1 of the second optical splitter, and a port of the second optical splitter A wiring connecting the first optical splitter to a port of the first optical splitter; a first light receiving module having an input side connected to the port of the second optical splitter; and a second optical splitter. A second light receiving module whose input side is connected to port 4 of the An input terminal connected to the port 1 of the optical splitter for receiving an optical input signal, and a port 2 of the first optical splitter
And an output terminal connected to the output terminal for transmitting an amplified optical output signal. 2. The light receiving module according to claim 1, wherein the first light receiving module monitors the light input signal and the reflected light of the light output signal, and the second light receiving module monitors the light output signal. 2. The optical amplifier according to 1.