100Base-BX is a Fast Ethernet interface that operates with a single single- mode fiber. The bidirectional transmission takes place on two wavelengths, namely on 1,550 nm for the downstream and on 1,310 nm for the upstream. The insertion loss is 5.5 dB (downstream) and 6.0 dB (upstream). The signals are fed into the single mode fiber via a splitter. The data rate is 100 Mbit/s, the bridgeable distance can be 10 km, 20 km or 40 km.