Analysis of Common Causes of Optical Module Damage
1. Optical port pollution and damage
The pollution and damage of the optical interface cause the loss of the optical link to increase, resulting in the failure of the optical link. The reasons are:
a. The optical port of the optical module is exposed to the environment, and the optical port is polluted by dust entering;
b. The end face of the optical fiber connector used has been polluted, and the optical port of the optical module has been polluted twice;
c. Improper use of the end face of the optical connector with pigtail, scratches on the end face, etc.;
d. Use inferior fiber optic connectors;
e. Improper plugging and unplugging, broken ceramic sleeve, etc.
f. Abnormal operations, such as: non-hot-swappable optical module live operation; direct contact with the static-sensitive pins of the optical module without electrostatic protection; no anti-static packaging during transportation and storage;
g. The equipment is not grounded or is poorly grounded.
2. Matters needing attention during the use of optical modules
The optical module integrates sophisticated optical components and circuit components. During daily use, attention must be paid to operating according to the specifications, otherwise it will easily cause damage to the optical module. The following is an introduction to the daily use precautions of the optical module:
1. Correct installation of the module
a. Make sure the module is properly installed. When installing the optical module, insert the module firmly to the bottom. If you hear a "pop" sound or feel a slight vibration, it means that the module is locked in place. When the optical module lock is not locked in place, the gold finger is slightly in contact with the connector on the board, and the link may be connected. However, in the case of vibration, collision, etc., the optical module will be disconnected or even loosen and other faults;
b. There are ceramic parts inside the optical module. Be careful when handling the optical module. If it is accidentally dropped or bumped hard, the optical module is not recommended to be used on the shelf again to avoid subsequent failures;
c. When inserting the optical fiber cable into the optical module, it is required to move gently and insert it directly to the optical port. If you insert it with too much force or obliquely, the optical module may be damaged;
d. Most optical modules support hot-swapping, but frequent hot-swapping is not recommended, which may easily cause electrical damage;
e. Confirm the action specification of plugging and unplugging the optical module: when taking out the optical module, do not touch the golden finger part of the optical module to avoid damage to the optical module; when inserting the optical module, make sure that the handle of the optical module is attached to the optical port of the optical module Then insert it; when pulling out the optical module, first pull out the optical fiber cable, pull the handle to a position about 90 degrees from the optical port, and then pull it out slowly. Do not pull out too hard or pull out the handle before it is in place. The shielding cover of the optical module is damaged.
2. Prevent module optical port pollution
a. Try to choose high-quality fiber optic connectors;
b. Before using the optical fiber jumper connector inserted into the optical module, it is best to wipe it with high-purity alcohol cotton to avoid cross-contamination of the optical port due to contamination of the end face of the optical jumper;
c. Avoid long-term exposure of the optical module. When not in use, the fiber jumper and optical module must be plugged with dust caps in time to prevent dust from entering the optical module and affecting its performance. Store the dust cap in a dust-proof and clean place when not in use;
d. The insertion of the optical fiber connector is aligned with the optical port horizontally to avoid scratches on the end face and the sleeve;
e. Keep the end face of the fiber optic connector clean and avoid scratches.
3. Prevent electrostatic damage
4. Pay attention to the light saturation of the long-distance module
For long-distance optical modules, since their average output optical power is generally greater than their maximum input optical power (that is, optical saturation), users should pay attention to the length of the optical fiber when using it. The -20dB optical signal attenuator effectively attenuates the fiber signal strength to ensure that the actual received optical power of the optical module is less than its optical saturation, otherwise it may cause damage to important components of the optical module.
5. Avoid mixing multi-mode and single-mode fibers
The multi-mode module uses multi-mode fiber, and the single-mode module uses single-mode fiber. In the case of mixed use, failures such as signal loss may occur.
6. Single-fiber bidirectional module to avoid wavelength confusion
Single-fiber bidirectional modules are used in pairs. The transmitting wavelength of device A and the receiving wavelength of device B must be the same. If the wavelengths are confused, there will be failures such as link failure.
7. The voltage is wrong
There are two power supply methods for 1x9 optical modules, 3.3V and 5V. There is only one power supply method for SFF SFP optical modules, which is 3.3V. If the voltage supply is wrong, the optical path will be blocked, and the voltage will increase or even burn out the module.
3. Common judgment steps for optical module damage
1. Test whether the optical power is within the required range of the index, if there is no light or low optical power.
Approach:
a. Check the wavelength and measurement unit (dBm) of optical power selection
b. Clean the end face of the optical fiber connector and the optical port of the optical module.
c. Check whether the end face of the fiber optic connector is black and scratched, whether the fiber optic connector is broken, and replace the fiber optic connector for an interchangeability test
d. Check whether there is a small bend in the fiber optic connector.
e. The hot-swappable optical module can be re-plugged and tested.
f. Replace the optical module on the same port or replace the port test on the same optical module.
