This value reports the measured loss of the fiber span associated with the OTS interface, expressed in optical dB and specifically excluding any configured offset. Span loss is one of the most direct indicators of fiber health an optical engineer has, since a rising value points to a developing problem such as a bad splice, a dirty connector, or fiber bending. If measured span loss on an OTS suddenly jumps by several dB compared to its commissioned baseline, the operator knows to dispatch a technician to inspect that fiber run before it causes service-affecting errors.