Failure to support the ALS function by RPC?

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Question:
Why RPC does not support the ALS function?
Analysis:
To support the ALS function, RPC must be able to accurately detect fiber cuts. Theoretically, there are two methods of detecting fiber cuts:
1. Check optical power. If the RPC receive optical power is less than a certain value, a fiber cut occurs.
2. Check the reflection value. If the RPC receive reflection power is greater than a certain value, a fiber cut occurs.
The RPC receive optical power is dependent on the number of wavelengths, line attenuation, and RPC gain. If a fiber cut point is far from the RPC, the pump light in optical cables can be greatly amplified. In this case, the RPC receive optical power contains large noise power. For the reasons above, the difficulty in determining a fiber cut based on the power strength lies in that a critical power value for judging a fiber cut cannot be determined. To be specific, it is unreliable to determine an RPC fiber cut based on the power strength.
The reflection value is dependent on the end face of the fiber cut point. There are two types of fiber cuts:
a. A connector is disconnected. If a PC connector is disconnected from an optical port, large reflection power is generated. A fiber cut can be determined based on the reflection power. However, the LINE port of the RPC board is equipped with an APC connector that is applicable to high-power applications. Small reflection power is generated even though the APC connector is disconnected. Therefore, the reflection power cannot be used as the basis of a fiber cut.
b. An optical cable is broken. The reflection power generated upon a cable break is random and is small in most cases. Therefore, the reflection power cannot be used as the basis of a fiber cut.
Based on the preceding reasons, it is unreliable to implement the ALS function only using the RPC board.
Answer:
Use the IPA function to disable the laser of the RPC board upon a fiber cut.
Suggestion and conclusion:
None

Other related questions:
LPT/ALS functions and differences between them
After ALS is enabled, when a fault occurs on the client or WDM side, the laser on the optical port in the corresponding transmit direction will be turned off. The laser will be recovered after signals in the receive direction are restored to normal. With the ALS function enabled, fault information can be sent to notify client equipment of the link status. The LPT function applies to scenarios in which WDM equipment receives FE, GE, or 10GE LAN services. With the LPT function, lasers on WDM equipment are alternately turned on and off. The on/off status of the lasers enables devices to know the link status. The devices will trigger service protection when detecting an unexpected link state, and switch services to the working or protection link to avoid service interruption. From the network layer perspective, the ALS function is similar to the LPT function. The main differences lie in applicable services, fault information transmission modes, and the laser restart mechanisms.

Whether the TQX board supports ALS
Yes, the TQX board supports ALS. After ALS is enabled, when a fault occurs on the client or WDM side, the laser on the optical port in the corresponding transmit direction will be turned off. The laser will be recovered after signals in the receive direction are restored to normal. With the ALS function enabled, fault information can be sent to notify client equipment of the link status. By default, ALS is enabled on boards.

ALS switching time
ALS has two parameters related to time: Hold-off Time of Automatic Laser Shutdown: indicates the period from the time when the system detects service interruption to the time when ALS automatically turns off the related lasers, with ALS enabled. Hold-off Time of Automatic Laser Turn-On: indicates the period from the time when the system detects service restoration to the time when ALS automatically turns on the related lasers, with ALS enabled. For each parameter, the value ranges from 0s to 2s, the step is 100 ms, and the default value is 0s.

Do CE series switches support the FC function
CE series switches support the FC function in V100R005C10 and later versions. Currently, only the CE6850U-HI supports the FC function.

Automatic laser shutdown on the SL64 board of the OSN 9500
When one end does not receive optical signals, it reports an R_LOS alarm to automatically shut down the laser, and the peer end shuts down its laser after receiving the R_LOS alarm. To ensure that light emitting can be immediately recovered after a fault is rectified, the lasers on the ports at both ends are turned on every other minute and the turn-on state of the lasers is kept for 2 seconds. If the fault persists, the lasers will be kept shutdown for 1 minute. The lasers at both ends are recovered if optical signals can be received immediately after the fault is rectified.

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