Description of the problem

Services are mapped from Huawei OSN1500 device SSN1PL301 into N4SL64 on Huawei 1500 network element, which is connected to OSN7500 network element. The 7500 network element then carries customer B's services to London over the submarine cable using STM-1 links to other OSN nodes. Customer A reports that the SSN1PL301 board on the 3500 network element reports a P_LOS alarm for 30 seconds continuously one day, and during this period, user B's service is affected.

The SSN1PL301 board on the 1500 network element reports a P_LOS alarm to the network administrator, indicating a loss of signal.

Processing

The following may be the cause of the problem: 1. Interface board failure; 2. Loose interface board slot; 3. Loose connection on the DDF; 4. Poor grounding. These problems may occur on our equipment endpoints.

On the user B side of the service provided by customer A, the possible causes are as follows: 1) DS3 board failure of the device; 2) poor grounding of the device; 3) loose interface board slot; 4) the cable from the DDF to the device is too long, and the single board does not support such a long length.

Root cause

Cable length is too long

Solution

We should first check the cable length from our DDF rack to the location of user B's equipment. If the cable length is more than 70 meters, we should ask the customer to reposition the equipment so that the cable length is less than 50 meters; if the cable length is within 50 meters, continue to position the equipment as follows:

If there is an alarm, hard loop back to the corresponding VC-3 on the DDF frame and check whether the alarm disappears;

If the alarm does not disappear, the possible reasons for the power failure of our equipment mentioned above, such as poor grounding, loose interface connections, loose interface slots and loose connections on the DDF rack, will be obvious;

If the alarm disappears, the cause of the problem is not on our equipment endpoints, and other causes need to be located, and User B should be asked to check the status of the DS3 veneer boards, grounding and connections.

Suggestions and Summary

The P_LOS alarm is caused by a cable that is too long (more than 70 meters), and the user's equipment does not support such a long cable length. Therefore, it is recommended to keep the cable length within 50 meters to avoid problems caused by different support situations.

The related technical information in this chapter and the SDH equipment troubleshooting procedures are collected and organized by Shenzhen Optical Transmission Network Technology Company Limited ( www.opticaltrans.com), and are reproduced and retained! Our company specializes in the sale of Huawei SDH optical transmission equipment, SDH transmission equipment.