How to Maintain Optical Fiber Amplifiers?

Figure 1: A sample of an Amonics standard erbium doped fiber amplifier.

An optical fiber amplifier (OFA) can not only directly amplify optical signals, but also have the advantages of real-time, high gain, online, low noise and low loss. It is an indispensable key device in the new generation of optical fiber communication system. At present, there are mainly erbium doped fiber amplifiers (EDFA), semiconductor optical amplifiers (SOA) and fiber Raman amplifiers (FRA) in practical fiber amplifiers.
OFAs are critical in fiber optic communication systems, but they are also prone to failures. This article briefly introduces some common failures, solutions and maintenance methods.

Common Optical Fiber Amplifier Failures and Solutions

1. The output power decreases. Due to improper use by users, such as plugging and unplugging when the machine is working, the pigtail head output by the OFA will be burned, resulting in a decrease in the output power of the OFA. If this happens, just re-fuse the output connector of the OFA.

Figure 2: A potential cause of poor transmission of optical fiber amplifiers.

2. The optical power meter is inaccurate. Some optical power meters can only test devices with low optical power output, but cannot test EDFAs with high power output. Therefore, it is necessary to use an accurate, original optical power meter to test.
3. The flange of the output port is damaged, but this possibility is small. Just replace it.
4. The quality of the pigtail used by the user is too poor and the fiber core is too long. The inserted pigtail scratches the output connector of the OFA. It is normal at the first test, but the optical power drops at the second test. To solve this problem, one needs to re-fuse the output connector of the OFA.
5. The optical power of the input OFA is small. If it is lower than the standard value, the optical power may become smaller, which will be displayed on the panel. Adjusting the input optical power can help to solve the problem.
6. The wavelength of the light source is wrong. If the wavelength of the 1550nm optical transmitter is deviated, the output optical power of the OFA will be insufficient, and the panel display will be too small. Therefore, the wavelength of the light source needs to be adjusted.

Tips for Maintenance of Optical Fiber Amplifiers

Proper, regular maintenance is essential to prolong the life of the equipment and to give full play to its functions. Here are a few maintenance suggestions for OFAs.

Figure 3: Regular maintenance is necessary for optical fiber amplifiers.

1. Measure the input optical power and make a record. The input optical power range of the EDFA provided by the manufacturer is wide. However, in order to obtain a suitable carrier-to-noise ratio index, the input optical power of the EDFA should be increased as much as allowed by the maximum index. Generally, it should not be lower than 3dB.
2. Under the condition of shutdown, wipe the end face of the pigtail and plug in the input pigtail. Connect the optical power meter with a pigtail that matches the output of the OFA. The output power of the power-on test should be consistent with the output optical power of the OFA.
3. After shutting down again, connect the pigtail to the optical splitter. Measure the output optical power of each channel of the splitter and make a record.
4. Due to the high output power of the OFA, plugging and unplugging the pigtail and wiping the end face of the pigtail must be performed under the condition of shutdown. Otherwise, the end face of the optical transmitter module or the output pigtail of the optical module will be damaged due to the high reflected power.

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