Huawei N2SLQ16 Board Interconnected with the TQS Board Reports an R_LOS Alarm

Symptom

When Huawei N2SLQ16 board on an Huawei OptiX OSN 7500 NE is interconnected with the TQS board on an OptiX OSN 6800 NE at an office and no service is deployed on the TQS board, the N2SLQ16 board reports an R_LOS alarm when the optical power is normal. After a software outloop is performed on the TQS board, the alarm reported on the N2SLQ16 board is changed to R_LOF.

Cause Analyze

No service is deployed on the TQS board. Therefore, an R_LOF not an R_LOS alarm should be reported when the TQS board is interconnected with the N2SLQ16 board and when the optical power is normal. Since the N2SLQ16 is not faulty, the possible cause of the R_LOS alarm is that signals are lost rather than that the optical power is abnormal. That is, the N2SLQ16 board may receive white lights.

Under the condition that signals are scrambled but not framed on the TQS board, the initial values of the output signals on the WDM side of the TQS board are all zero. At this time, the optical module on the TQS board outputs white lights. When a loopback is performed on the TQS board, that is, signals on the optical module are framed and scrambled for initialization, the TQS no longer outputs white lights but random signal lights. As a result, the downstream N2SLQ16 board does not report the R_LOS alarm.

Procedure

1.         Query the alarm mode of the OptiX OSN 6800 NE on the T2000. The result shows that the alarm mode is set to automatic reversion for the NE but the automatic reversion function is not enabled at the optical interface.

2.         Replace the N2SLQ16 board or the optical module on the board but the problem persists. Perform a hardware loopback at the optical interfaces on the N2SLQ16 board by using an optical fiber. The R_LOS alarm disappears. The possibility that the N2SLQ16 board or the optical module on the board is faulty is excluded.

3.         Analyze that the TQS board interconnected with the N2SLQ16 board may be faulty. That is, the lights transmitted by the TQS board may be white, and therefore signals on the N2SLQ16 board are lost. On the T2000, set the client-side optical interfaces on the TQS board to Outloop. At this time, the alarm on the N2SLQ16 board is changed from R_LOS to R_LOF. The fault is rectified.

Introduction of CES Services on Huawei Optix OSN equipment

The circuit emulation service (CES) helps to solve the problem of insufficient optical fiber resources in the access ring and allows TDM services to be transparently transmitted across the pure packet mode.

At the physical layer on the UNI side, Huawei OptiX OSN equipment is interconnected with a CE through the following physical channels for accessing CES services:

• Channelized STM-1
• E1

Figure 1 Networking diagram of the CES 

As shown in Figure 1, the OptiX OSN equipment can gain access to CES services at emulation node 1, emulation node 2, or emulation node 3.

• At emulation node 1, the OptiX OSN 1500 transmits E1 services to the GE packet ring.
• At emulation node 2, the OptiX OSN 3500, OptiX OSN 7500 or OptiX OSN 7500 II transmits E1 signals that are received from the BTS through TDM STM-1/STM-4 ring to the 10GE packet ring.
• At emulation node 3, the OptiX OSN 3500, OptiX OSN 7500 or OptiX OSN 7500 II converts E1 CESs on the 10GE packet ring into STM-1 signals and then sends them to the BSC.

The OptiX OSN equipment supports both structure-aware TDM circuit emulation service over packet switched network (CESoPSN) and structure-agnostic TDM over packet (SAToP). Installation guide like OSN 3500 configuration guide can be found in the Hedex files.

In the case of CESoPSN, the features are as follows:

• The equipment is aware of frame structures, frame alignment modes, and timeslots in TDM circuits.
• The equipment processes the overheads in and extracts the payloads from the TDM frames. Then, the equipment loads timeslots to the packet payload in a specific sequence. As a result, the services in each timeslot are fixed and visible in packets.

In the case of SAToP, the features are as follows:

• The equipment is agnostic about the structures of the TDM signals. To be specific, the equipment treats TDM signals as constant bit-rate (CBR) flows, and emulates all the TDM signals in the same way.
• The overheads and payloads in TDM signals are transparently transmitted.