the R_LOF Alarm Is Reported in the Receive Direction on the Client Side When the Laser

In a WDM system with 1:N optical channel protection, the R_LOF alarm is reported in the receive direction on the client side when the laser on the LWC1 board in the protection channel is open.

Product

OSN6800,OSN8800,WDM

Fault Type

Optical Transponder Unit

R_LOF

Symptom

In the OptiX BWS 1600G system, the NE software version is 5.08.03.11. The networking topology is a chain: station A -> station B -> station C. Stations A and C are two OTM stations. The OCP board is used to provide 1:N optical channel protection.

One day, the boards in the SDH equipment interconnected with the LWC1 board in the OptiX BWS 1600G system reported the R_LOF alarm. Then, the receive and transmit optical power of this board was measured. The measurement result showed that the optical power was within the normal range. The MCA board was connected to the MON interface on the D40 board to test the optical signal-to-noise (OSNR) and optical power of the LWC1 board. The test result showed that the OSNR and optical power were also within the normal range.

Cause Analysis

A 1:N optical channel protection group uses a protocol to control protection switching (including the opening and closing of the laser). Normally, the laser in the protection channel of the LWC1 board is close.

The OCP is just an optical coupler. If 1:N optical channel protection is not switched and Laser Status at the client-side optical interface on the LWC1 board in the protection channel is Open, the optical signals in the working channels are coupled with those in the protection channel and thus abnormal optical signals are output. As a result, the SDH equipment fails to identify the output signals and the boards in the SDH equipment report the R_LOF alarm.

Procedure

1. The boards in the SDH equipment report the R_LOF alarm. This alarm indicates that optical signals are received but the signals are abnormal.
2. Connect an MCA board to the MON interface of the D40 board. Both the optical power and the OSNR of the LWC1 board are normal. This indicates that a wavelength is normally dropped from the main optical path to the D40 board.
3. The OCP board connects the LWC1 board to the SDH equipment to provide 1:N optical channel protection. The LWC1-OCP-SDH equipment section may be faulty.
4. Self-loop the two S16 boards and the two LWC boards. No abnormal alarm is reported. Therefore, the boards are normal.
5. The OCP board may be faulty. Check the wavelength configuration of the 1:N optical channel protection group. The check result shows that the wavelength configuration is normal. Check the configuration of the LWC1 boards in the working and protection channels. The check result shows that Laser Status at the client-side optical interface on the LWC1 board in the protection channel is Open and Automatic Laser Shutdown at this interface is Disabled.
6. 1:N wavelength protection switching is controlled by the protection protocol. Normally, the laser of the LWC1 board on the protection channel is shut down. The OCP is an optical coupler. If the protection channel is enabled, the OCP couples the optical signals of the working channel and the protection channel. When improper optical signals are output, the SDH equipment cannot identify the output optical signals and thus reports the R_LOF alarm.
7. Set Laser Status at the client-side optical interface on the LWC1 board in the protection channel to Close and set Automatic Laser Shutdown at this interface to Enabled.

Result

The R_LOF alarm reported by the boards in the SDH equipment is cleared. That is, the problem is solved.

Reference Information

None.

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