Whether G.652B fibers can be used on DWDM networks

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All G.652 fibers can be used on DWDM networks, regardless of whether the fibers are G.652 A, B, C, or D.
The most commonly used fibers are G.652D fibers, which have a better attenuation coefficient than G.652B fibers.

Other related questions:
Whether G.652 fibers can be used for NS4 boards
G.652 fibers can be used if the door of the cabinet housing the NS4 boards can be properly closed.

Whether the 100 G WDM equipment can use the OTDR to detect fiber cuts
The equipment supports the FD since V100R009. This function requires the TN12ST2 and TN13FIU boards, U2000 license, and MDS 6630.

Dispersion compensation for hybrid use of G.652 and G.655 fibers.
The G.652 and G.655 fibers have different dispersion coefficients. The dispersion coefficient of the G.652 fiber is 17 ps/nm.km, and the dispersion coefficient of the G.655 fiber is 4.517 ps/nm.km. When the G.652 and G.655 fibers are used together, the dispersion should be calculated respectively. The G.652-specific DCMs can be used to compensate for the dispersion of both G.652 and G.655 fibers. You can divide the length of the G.655 fiber by 4, and then determine the DCM type based on the calculation result.

Differences between G.653 and G.655 fibers in fiber measurement
Question: Fiber measurement is usually required in engineering commissioning of 40G WDM and 10G WDM systems. In guide documents, parameters to be measured are attenuation, CD value, and PMD value. In practice, zero dispersion slope is also an important parameter that must be measured. This parameter can be used to distinguish between G.653 fibers and G.655 fibers. Analysis: Understanding how to distinguish between G.653 fibers and G.655 fibers through fiber measurements is important because the two types of fibers require different incident optical power. G.653 fibers impose strict requirements on incident optical power. If incident optical power does not meet specified requirements, non-linear effects are serious, which results in a high bit error rate (BER), low optical signal-to-noise ratio (OSNR), or even a service interruption. Root cause: None Answer: The specifications of the two types of fibers are as follows: 1. The G.653 fiber is also called dispersion-shifted fiber. Its typical specifications are as follows: In the 1310 nm window, the attenuation coefficient is 0.55 dB/km and no typical value is available currently. In the 1550 nm window, the attenuation coefficient is 0.35 dB/km and the value is usually within the range of 0.19 dB/km to 0.25 dB/km. The zero dispersion point is in the range of 1525 nm to 1575 nm and the dispersion coefficient in this range is smaller than 3.5 ps/(nm/km). G.653 fibers have optimal features in the 1550 nm window and therefore are preferred for single-wavelength and ultra long-haul transmission. 2. The G.655 fiber is also called non-zero dispersion-shift fiber (NZDSF). The zero dispersion point is moved several wavelengths away from 1550 nm so that the zero dispersion point is not in the working wavelength range near 1550 nm. Its typical specifications are as follows: In the 1310 nm window, the attenuation coefficient is 0.55 dB/km and no typical value is available currently. In the 1550 nm window, the attenuation coefficient is 0.35 dB/km and the value is usually within the range of 0.19 dB/km to 0.25 dB/km. The dispersion coefficient absolute value is between 1.0 to 10.0 ps/(nm/km). 3. According to the preceding specifications, the attenuation coefficient and CD value of G.653 fibers are not very different from those of G.655 fibers. Actually, the value range of the attenuation coefficient and CD value of G.653 fibers overlaps with that of G.655 fibers. The actual specifications of fibers are determined by manufacturers. The PMD value depends on the quality of fibers. Therefore, you cannot distinguish between G.653 and G.655 fibers using only these parameters. 4. In this case, another parameter called maximum zero dispersion slope can be used to distinguish between G.653 and G.655 fibers. This parameter is essential to distinguishing fiber types. Each type of fiber has only a typical zero dispersion slope and the value is not fixed. The change of the value, however, is very small and this parameter is fiber-specific. Take G.653 and G.655 fibers as examples. Zero dispersion slopes of them are as follows: G.653: 0.07600 ps/(nm^2·km) G.655-LEAF: 0.08365 ps/(nm^2·km) G.655-TWRS: 0.04780 ps/(nm^2·km) You can distinguish between G.653 and G.655 fibers by measuring zero dispersion slopes of them.

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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