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. Understanding where those losses come from, and how to calculate them, is essential for designing a link that actually works. However, there are general guidelines and considerations that can help. In optical fiber systems, the acceptable dB loss is determined based on the fiber type, application, and distance of transmission. The maximum loss value according to TIA standards is 0. Do not count the mechanical splice.