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One-Way Audio Exists When the NE40 Is Interconnected to the Third-Party s AG

Publication Date:  2012-07-27 Views:  86 Downloads:  0
Issue Description
Version information: Version 3.10, RELEASE 2351
Symptom: In the NGN bearer network of China Telecom, one NE40 is connected to a GE port on the third party’s AG. The physical port on the NE40 is Down while the physical port on the AG is Up. As a result, one-way audio happens. 
Alarm Information
Handling Process
1. The NE40 and the AG are directly connected through an ODF. After the transmit fiber and receive fiber on both sides are replaced, one-way audio still exists. Therefore, it is ruled out that the tail fiber is faulty.
2. After near-end loopback is performed for the NE40 on the ODF, the physical port is Up. Meanwhile, the interconnected port on the S3552 switch is also Up, which indicates that the GBIC module is normal.
3. Use an optical power meter to measure the optical power transmitted from the AG. The measured optical power is �15 dB, which is in the normal reception range of the optical module.
4. From an AG engineer of the third party, it is learned that the optical module sends only optical signals when the AG is in the standby state. If the GE port on the NE40 is Up, the following conditions must be satisfied: 1) The port receives optical signals. There are transient data code streams on the link. If the port fails to receive any transient code streams (data code streams or idle code streams) on the link within 10 ms, the port will be Down.
Since the link from the NE40 to the AG is standby and the port on the NE40 does not receive any data code streams, the port is physically Down all the time. 
Root Cause
The possible causes are as follows:
1. The tail fiber is faulty.
2. The GBIC module on the NE40 is faulty.
3. The optical power is too low or too high.
4. Others. 
 When an interconnection failure occurs, check not only the local end but also the peer end. In addition, learn the working mechanisms of the AG and the NE40.