Precautions for DWDM network maintenance

1. Exercise caution and apply proper force to prevent pins on the backplane from bending when removing and reinserting, or replacing a board. If pins are bent, a short circuit may cause service interruption in the system, resulting in huge loss. Wear an ESD wrist strap at all times when touching a board.
2. Before replacing a board, check whether the to-be-inserted board and the to-be-removed board are of the same type, and whether their working features are the same. Because different OTU boards output different optical wavelengths, do not randomly interchange the boards. Use boards of the same type and output optical wavelength for replacement. Optical multiplexer/demultiplexer boards, optical amplifier boards, and optical add/drop multiplexing boards are classified into different sub-categories in terms of working band and working feature. Always use boards of the same type for replacement.
3. When a board is running abnormally, you can perform a warm or cold reset on the board. You can reset the board using either way. Note that the reset operation will adversely affect the communication between the board and the system control board, and may even interrupt the services. Always be cautious if you must reset a board. In the equipment room, you can perform a cold reset by reseating a board. As to the SCC board, you can also press the RST button on the front panel to perform a cold reset. Generally, you are advised to reset a board using the NMS.
4. Periodically clean air filters. Each air filter of a fan tray assembly is equipped with a handle. To remove the air filter, firmly grasp and pull the handle. After removing the air filter, clean it with water and a dry cloth. Then, allow it to dry in an area with proper ventilation. After cleaning the air filter, re-insert it into the fan tray assembly along guide rails at the bottom of the subrack. When pushing the air filter, apply only proper force. Do not shut down the fan power supply.
5. Protect unused optical ports on an OA board with protective caps. This prevents personal injuries and protects optical ports against dust. When a fiber jumper is not used, protect the connectors on both ends of the fiber jumper with protective caps. When removing or inserting optical fibers or performing a line fiber cutover, clean optical fiber connectors and optical ports with dust-free fiber cleaning tissues or fiber cleaning kits. In addition, ensure that the optical power does not deteriorate.
6. Do not look into an optical port without wearing protective glasses to protect your eyes against laser radiation, especially in the case of an OA board, which outputs invisible light with high optical power.
7. When applying a fiber loopback between the receive and transmit optical ports, use an optical attenuator between the two ports to prevent the receiver from being damaged because of excessively high input optical power.
8. During routine maintenance, if you need to adjust the mechanical VOA, note that clockwise adjustment increases the attenuation value and decreases the output optical power, whereas counterclockwise adjustment decreases the attenuation value and increases the output optical power. Because the mechanical VOA has high sensitivity, adjust its attenuation slowly and apply a steady force to avoid an abrupt increase or decrease in the optical power that will affect services, and may even damage the attenuator.
9. A DWDM system is sensitive to optical power. If a fiber jumper is excessively bent or squeezed, the optical power will deteriorate. Always ensure that the bending radius of a fiber jumper inside a cabinet is greater than 4 cm and that of a fiber jumper outside a cabinet is greater than 6 cm.
10. If wavelength switching is required for fault location or emergent service restoration, the transmit and receive wavelengths must be consistent.

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