JPH0974242A - Optical amplifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lessen the loss of monitoring signal light without increasing the loss of main signal light, which is inputted, by a method wherein preceding-step and succeeding-step optical branching means are constituted so that they exhibit different characteristics in a branch ratio to the main signal light and a branch ratio to the monitoring signal light. SOLUTION: The branch ratio in optical branching circuits 11 and 12 is changed. That is, in the circuits 11 and 12, the ranch ratio is changed so that main signal light is branched in a ratio of 10:1 and monitoring signal light, is branched in a ratio of 1:10. Thereby, the main signal light results in being outputted at a rate of '10' to an optical amplification part 2 to '1' to a photo multiplexer 3 and the monitoring signal light results in being outputted at a rate of '1' to the part 2 to 1 '10' to the multiplexer 2. As the circuits 11 and 12, one consisting of a multilayer film or an optical fiber fusion-bonded one is applied. The main signal light and the monitoring signal light, which are branched in the circuit 11 having such the branch ratio, are separated from each other by the photo multiplexer 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical amplifier applied as an optical amplification intermediate repeater in an optical communication system of a trunk system and a subscriber system.

In the case of supervisory control of an optical amplifier used as such a repeater, a supervisory control (SV) signal is put on light having a wavelength different from the wavelength of the main signal light, and the wavelength at which the SV signal is received by the optical amplifier. A multiplexing method is used, and it is desired that the insertion loss of the SV signal light can be reduced without increasing the insertion loss of the main signal light.

[0003]

2. Description of the Related Art FIG. 4 shows a block diagram of an optical amplifier used as a conventional optical amplification intermediate repeater, and its description will be given.

In this figure, 1 and 8 are optical branch circuits and 2
Is an optical amplification section, 3 is an optical multiplexer / demultiplexer, 4 is a PD (Photo Diode) for monitoring the main signal input light, 5 is an SV signal light receiving section, and 6 is an S
A V signal processing unit, 7 is an SV signal light transmitting unit, 9 is an SV signal light blocking filter, and 10 is a main signal output light monitoring PD.

The optical branching circuit 1 uses the wavelength division multiplexing method described in the above industrial application field to transmit the main signal light having a wavelength of 1.55 μm from a terminal station (not shown) and 1.48 μm.
The SV signal light in the m band is branched.

One of the branched lights is an optical multiplexer / demultiplexer 3
And the main signal light is separated by the PD4 for monitoring the main signal output light.
The SV signal light is input to the SV signal light receiver 5. S
The SV signal light is converted into an electric signal in the V signal light receiving unit 5, and the SV signal processing unit 6 is applied to the converted SV signal.
After the information is read / written by the SV signal light transmitter 7,
Is converted to light again.

The SV signal light sent from the SV signal light transmitter 7 is combined with the main signal light amplified by the optical amplifier 2 in the optical branching circuit 8 and sent to the transmission line. Further, the SV signal light blocking filter 9 blocks the SV signal light sent from the optical branching circuit 8, and the main signal light passing through this is input to the main signal output light monitoring PD 10.

Then, the power of the output main signal light is held constant by controlling the gain of the optical amplifier 2 according to the optical power obtained by the PD 10.

[0009]

By the way, the characteristics of the optical branch circuits 1 and 8 in the above-described optical amplifier have a branching ratio (for example, 10: 10) for both the main signal light and the SV signal light.
The same 1) is used, and the branching ratio is set so as to suppress the insertion loss of the main signal light as small as possible.

That is, when both lights are branched by the optical branching circuit 1 at a branching ratio of 10: 1, both lights are in the ratio of “10” to the optical amplifier 2 and “1” to the optical multiplexer / demultiplexer 3. Will be output.

Therefore, in the optical amplifier shown in FIG.
The insertion loss of the SV signal light increases, and the power of the SV signal light input to the SV signal light receiving unit 5 decreases. For this reason, there is a problem that the SV signal light receiving section 5 may not be properly converted into an electric signal, and the SV signal processing section 6 may not be able to obtain appropriate information.

In order to solve this problem, a method of improving the receiving sensitivity of the SV signal light receiving section 5 can be considered.
Since it is necessary to use parts such as a highly accurate light receiving element, the cost is high and it is not an appropriate solution.

A method of increasing the light emission power of the SV signal light transmitter 7 may be considered, but the power consumption increases or the power of the combined light with the main signal light sent from the optical branching circuit 8 is used as a reference. This method is not appropriate as it will exceed the limit.

The present invention has been made in view of the above circumstances, and reduces the loss of the SV signal light without increasing the loss of the input main signal light.
An object of the present invention is to provide an optical amplifier capable of properly reproducing information by V signal light.

[0015]

According to the present invention, a main signal light and a supervisory signal light having different wavelengths are branched by an optical branching means in the preceding stage, and one of the branched main signal light and supervisory signal light is the main signal light. Amplifies only the constant signal light, and the other main signal light and the supervisory signal light take out only the supervisory signal light, convert it to an electric signal, perform a predetermined process and convert it again to light, and then amplify it by the optical branching means in the subsequent stage. In the optical amplifier for sending out the main signal light to the transmission path together with the main signal light, the optical branching means at the front and rear stages are configured to show different characteristics depending on the branching ratio for the main signal light and the branching ratio for the monitoring signal light.

Further, the branching ratio of the above-mentioned optical branching means is such that the main signal light is branched to a large amount on the amplification side, and the monitor signal light is converted into the electric signal. It is preferable that a large number of branches be provided on the side of the vehicle.

[0017]

According to the present invention described above, when the main signal light and the supervisory signal light having different wavelengths are branched by the optical branching means at the preceding stage, the main signal light is largely branched to the amplification side, and the supervisory signal light is monitored. Since a large amount of signal light is branched to the side where it is converted to an electrical signal, when the branched monitoring signal light is converted to an electrical signal, light of sufficient power is converted to an electrical signal, so that the signal due to the light is generated. It will be converted to an electrical signal properly,
Subsequent processing is performed appropriately.

Therefore, unlike the conventional case, since the power of the branched supervisory signal light is weak, it is not converted into a proper electric signal and proper processing cannot be performed.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a block diagram of an optical amplifier used as an optical amplification intermediate repeater according to the first embodiment of the present invention. In this figure, the parts corresponding to the parts of the conventional example shown in FIG. 4 are designated by the same reference numerals, and the description thereof will be omitted.

The optical amplifier of the first embodiment shown in FIG.
The difference from the conventional example shown in FIG. 9 is that the branching ratios of the optical branching circuits 11 and 12 are changed. That is, the optical branching circuits 1 and 8 in FIG. 4 have the same branching ratios of 10: 1 for both the main signal light in the wavelength band of 1.55 μm and the SV signal light in the wavelength band of 1.48 μm. Optical branch circuit 11, 12
Then, the main signal light is split at 10: 1 and the SV signal light is split at 1:
The reason is that it is branched at 10. By this,
The main signal light is output to the optical amplifier 2 at a rate of “10” and the optical multiplexer / demultiplexer 3 at a ratio of “1”, and the SV signal light is output to the optical amplifier 2 at “1” and the optical multiplexer / demultiplexer 3 at “10”. Will be output at the ratio of.

The optical branch circuits 11 and 12 are formed of a multilayer film or an optical fiber fusion type. The main signal light and the SV signal light branched in the optical branching circuit 11 having such a branching ratio are separated by the optical multiplexer / demultiplexer 3. Here, the crosstalk is 20 dB or more, and the mutual influence between the main signal and the SV signal is prevented.

The separated SV signal light is input to the SV signal light receiving section 5 and converted into an electric signal, but since the insertion loss in the optical branching circuit 11 is small, it is converted to the SV signal light receiving section 5. SV signal light having sufficient power to perform the above is input.

Therefore, since the SV signal light is converted into the electric signal properly, the SV signal processing section 6 can obtain proper information. In addition, the SV signal processing unit 6
The SV signal output from the SV signal light is converted into SV signal light by the SV signal light transmitter 7, and is branched by the optical branching circuit 12 at a ratio of "1" toward the SV signal light blocking filter 9 and "10" toward the transmission path. The SV signal light branched in the direction of the transmission path is combined with the main signal light sent from the optical amplification section 2 and sent out to the transmission path.

According to the optical amplifier having such a configuration, the insertion loss of the SV signal light can be reduced by 20 dB or more as compared with the conventional configuration. Next, an optical amplifier used as an optical amplification intermediate repeater according to the second embodiment will be described with reference to FIG. However, in FIG. 2, parts corresponding to the respective parts of the first embodiment shown in FIG. 1 are designated by the same reference numerals, and description thereof will be omitted.

The optical amplifier of the second embodiment shown in FIG. 2 is characterized in that the optical branch circuit 1 or 8 shown in FIG. The main signal output optical monitor PD 1 is provided on one output side of the optical branching circuit 13.
0 is connected, and the optical multiplexer / demultiplexer 14 is connected to the other output side,
Further, the SV signal light transmitter 7 is connected to the other input side of the optical multiplexer / demultiplexer 14.
The output side of is connected.

In such a configuration, the main signal light output from the optical amplifier 2 is sent to the transmission line via the optical branching circuit 13 and the optical multiplexer / demultiplexer 14, so that the loss of the main signal light is reduced. Although slightly increased, the SV signal light output from the SV signal light transmission unit 7 is directly combined with the main signal light by the optical multiplexer / demultiplexer 14, so that the SV signal light of the first embodiment is further increased. The loss can be reduced.

Next, an optical amplifier used as an optical amplification intermediate repeater according to the third embodiment will be described with reference to FIG.
However, in FIG. 3, parts corresponding to the respective parts of the first embodiment shown in FIG. 1 are designated by the same reference numerals, and description thereof will be omitted.

The optical amplifier of the third embodiment shown in FIG. 3 is characterized in that the optical amplification section 20 for amplifying the main signal light is constructed by using an optical amplification fiber (Er-doped fiber) 21 by bidirectional pumping. is there.

The optical amplification section 20 includes an optical multiplexer / demultiplexer 22 for forward pumping connected to the output side of an optical multiplexer / demultiplexer 31 to which the main signal light and the SV signal light are input, and the optical multiplexer / demultiplexer 22. An optical multiplexer / demultiplexer 23 for backward excitation, which is connected to the output side via an optical amplification fiber 21, an excitation light source 24 for supplying excitation light to the optical multiplexer / demultiplexer 22, and an optical multiplexer / demultiplexer 23. And an excitation light source 25 for supplying light.

The other components of the optical amplifier are SV signal light blocking filters 32 and 35, and a main signal input light monitoring PD3.
3, an SV signal light receiving unit 5, an SV signal processing unit 6, and an SV signal light receiving unit 5.
A V signal light transmitter 7, an optical branching circuit 34, and a main signal output light monitor PD 36.

However, the optical branch circuits 31 and 34 are assumed to have the same branching ratio of 10: 1 as the optical branch circuit 1 or 8 shown in FIG. First, the main signal light and the SV signal light are transmitted to the optical branch circuit 34.
10: 1 and 10/1 are output to the optical multiplexer / demultiplexer 22, and both 1/10 optical signals are output to the SV signal light blocking filter 32.

In the SV signal light blocking filter 32, the SV signal light is blocked, and only the main signal light is input to the PD 33 for monitoring the main signal input light. On the other hand, the main signal light and the SV signal light branched to the optical multiplexer / demultiplexer 22 are separated here, and the SV signal light is converted into an electric signal by the SV signal light receiving unit 5 to obtain the SV signal light.
After the signal processing unit 6 performs a predetermined process, the SV signal light transmitting unit 7 converts the light into SV signal light, which is input to the optical multiplexer / demultiplexer 23 and multiplexed with the main signal light.

The combined main signal light and SV signal light are split into 10: 1 by the optical branching circuit 34, and both of the split lights of 10/1 are sent out to the transmission path and are split into 1/10. Both of the split lights are output to the SV signal light blocking filter 35.

The SV signal light blocking filter 35 blocks the SV signal light, and only the main signal light is used as the main signal output light monitoring P.
Input to D36. Then, the power of the pumping light output from the pumping light sources 24 and 25 is controlled according to the optical power obtained by the PD 36, so that the power of the main signal light amplified by the optical amplification fiber 21 is held constant. It

According to this structure, the main signal light and the S
The V signal light is branched by the optical branching circuit 31, and 10 /
1 is output to the optical multiplexer / demultiplexer 22, where the main signal light and SV
The signal light is separated into the signal light and the separated SV signal light is input to the SV signal light receiver 5.

That is, since the SV signal light input to the SV signal light receiving section 5 has a small insertion loss in the optical branching circuit 31, the SV signal light receiving section 5 has sufficient power to convert it into an electric signal. It turns out that

Therefore, since the SV signal light is converted into the electric signal properly, the SV signal processing section 6 can obtain proper information. In addition, the SV signal processing unit 6
The SV signal output from is converted into SV signal light by the SV signal light transmitter 7, and after being multiplexed with the main signal light by the optical multiplexer / demultiplexer 23, it is directed to the SV signal light blocking filter 9 by the optical branching circuit 34. Since it is branched at a ratio of "1" and "10" in the transmission path direction, the main signal light and the SV signal light having sufficient power can be sent to the transmission path.

Therefore, according to the optical amplifier of the third embodiment, the insertion loss of the SV signal light can be reduced as compared with the conventional structure.

[0039]

As described above, according to the optical amplifier of the present invention, the loss of the SV signal light can be reduced without increasing the loss of the input main signal light.
There is an effect that information by the SV signal light can be properly reproduced.

[Brief description of drawings]

FIG. 1 is a block diagram of an optical amplifier used as an optical amplification intermediate repeater according to a first embodiment of the present invention.

FIG. 2 is a block diagram of an optical amplifier used as an optical amplification intermediate repeater according to a second embodiment of the present invention.

FIG. 3 is a block diagram of an optical amplifier used as an optical amplification intermediate repeater according to a third embodiment of the present invention.

FIG. 4 is a block diagram of an optical amplifier used as a conventional optical amplification intermediate repeater.

[Explanation of symbols]

 11, 12 Optical branching means 14 Optical multiplexing / demultiplexing means 21 Optical amplification fiber 22, 23 Pumping optical multiplexing / demultiplexing means

Front page continued (72) Inventor Norihisa Naganuma 1015 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa, Fujitsu Limited

Claims (4)

[Claims] 1. A main signal light and a supervisory signal light having different wavelengths are branched by a preceding optical branching means, and one of the branched main signal light and supervisory signal light constantly amplifies only the main signal light, and the other. As for the main signal light and the supervisory signal light, only the supervisory signal light is taken out, converted into an electric signal, subjected to a predetermined process and converted again into light, and then is transmitted to the transmission path together with the amplified main signal light by the optical branching means in the subsequent stage. In the optical amplifier for sending to the optical amplifier, the front and rear optical branching means (11, 12) have different branching ratios for the main signal light and the monitoring signal light. Optical amplifier. 2. The branching ratio of the preceding optical branching means (11) is
Many of the main signal lights are branched to the amplification side, and many of the supervisory signal lights are branched to the side where the supervisory signal lights are converted into electric signals. The optical amplifier according to claim 1. 3. Optical multiplexing / demultiplexing means for multiplexing the supervisory signal light and the main signal light in place of the optical branching means (12) in the latter stage.
The optical amplifier according to claim 1, further comprising (14). 4. An optical amplifier using an optical amplification fiber (21), wherein pumping optical multiplexing / demultiplexing means is connected in front of the optical amplification fiber for separating main signal light and supervisory signal light having different wavelengths. (22), the supervisory signal light separated by the pumping optical multiplexer / demultiplexer in the preceding stage is converted into an electric signal and subjected to predetermined processing, and then converted again into light, and the optical signal for amplification An optical amplifier comprising: a pumping optical multiplexing / demultiplexing means (23) connected to the subsequent stage of the optical amplification fiber for multiplexing the main signal light passing through the fiber.