What is the soak time period to detect LOS on a port?

To detect a failure that occurs at the source (e.g., laser failure) or the transmission facility (e.g., fiber cut), all incoming SONET signals are monitored for loss of physical-layer signal (optical or electrical). The detection of an LOS defect must take place within a reasonably short period of time for timely restoration of the transported payloads.

A SONET NE shall monitor all incoming SONET signals (before descrambling) for an “all-zeros patterns,” where an all-zeros pattern corresponds to no light pulses for OC-N optical interfaces and no voltage transitions for STS-1 and STS-3 electrical interfaces. An LOS defect shall be detected when an all-zeros pattern on the incoming SONET signal lasts 100 μs or longer. If an all-zeros pattern lasts 2.3 μs or less, an LOS defect shall not be detected. The treatment of all-zeros patterns lasting between 2.3 μs and 100 μs for the purpose of LOS defect detection is not specified and is therefore left to the choice of the equipment designer. For testing conformance to the LOS detection requirement, it is sufficient to apply an all-zeros pattern lasting at most 2.3 μs, and to apply an all-zeros pattern lasting at least 100 μs.