Fault Symptoms

A hop of 1+1 SD radio links provided by RTN 900 V100R003 was interrupted. The receive power of the main ODU of NE A was -90 dBm, and the link reported the RADIO_RSL_LOW and MW_LOF alarms. The receive power of the standby ODU of NE A was -40 dBm, which was a normal value. However, no protection switching occurred.

Procedure

***yzed the cause why protection switching did not occur. Checked the 1+1 SD protection group configurations, and found that reverse switching was enabled and the WTR time of the 1+1 SD protection was set to 10 minutes.
If a member link in a 1+1 protection group fails but no switching occurs, the cause is usually that the reverse switching timer has not expired.
Queried the receive power of the standby ODU of NE A, and found that the receive power was -40 dBm, which was a normal value. Forcibly switched services to the standby link on NE A. The services recovered.
Reverse switching occurs usually because a fault (such as a hardware fault) occurs in the transmit part at the source end but the equipment cannot detect the fault. Queried the transmit power and receive power of the main ODU of NE A. The transmit power was 23 dBm, which was a normal value; the receive power was still -90 dBm.
Replaced the main ODU of NE A and queried the receive power of the main ODU. The receiver power was still -90 dBm.
Replaced the flexible waveguide connected to the main ODU and queried the receive power of the main ODU. The receive power was still -90 dBm.
Checked the connections between the ODUs and antenna, and found a sign of water at the antenna feed port and then found water accumulated in the antenna feed. The accumulated water caused a failure to transmit RF signals.
Emptied the water in the antenna feed, dried it, and installed it again. Queried the receive power of the main ODU. The receive power was -35 dBm, which as a normal value.

Conclusions and Suggestions

To prevent repeated switching of a 1+1 protection group caused by fast fading, the reverse switching timer is configured. If the revertive mode is set for the 1+1 protection group, the length of the revertive switching timer is the same as the WTR time. If the non-revertive mode is set for the 1+1 protection group, the length of the revertive switching timer is set to 5 minutes.
Reverse switching occurs usually because a fault occurs in the transmit part at the source end.
Outdoor connectors (including connectors of flexible waveguides, IF cables, and RF cables, as well as ground clips) must be waterproofed in compliance with related specifications to prevent ingress of moisture or water.

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Helpful.....

thanks for this information its really helpful.......

Great !