Multimode Fiber: Typical allowable loss is 2. 9 dB for short-distance installations (100–300 meters). A 1,500-metre link with up to 3. 100Base-FX (100Mb Ethernet at 1300nm). For example, 10GBase-LX4 (10G Ethernet at 1300nm) allows a maximum loss of 2. The estimate, called a "loss budget" is calculated using typical component losses for. Fiber loss, or attenuation, refers to the reduction in optical power as light travels through a fiber optic cable. While some loss is expected, excessive or unexpected loss can lead to poor performance, network downtime, and signal failure. Cable loss (dB) = cable length (km) × attenuation coefficient (dB/km).