For singlemode fiber, the loss is about 0. 5 dB per km for 1310 nm sources, 0. 5 dB/km at either wavelength for outside plant max per EIA/TIA 568)This roughly translates into a loss of 0. 1. A: Fibre optic loss refers to the reduction in signal strength as it travels through the fibre optic cable. This can be due to various factors, including attenuation, connectors, and splices. Connector Losses: Also known as insertion losses, these occur when a device is inserted into a transmission line. The acceptable dB loss for single mode fiber can vary depending on several factors, including the specific application, the length of the fiber, the quality of the components used, and the overall design of the network. While some loss is expected, excessive or unexpected loss can lead to poor performance, network downtime, and signal failure.