Answer: Single-fiber bidirectional refers to the simultaneous transmission and reception of optical signals in two directions in one optical fiber. The optical modules used in wireless devices are all optical transceiver modules. The dual-fiber bidirectional optical module has two optical fiber connection ports, while the single-fiber bidirectional optical module has only one optical fiber connection port. Single fiber bidirectional is mainly realized by WDM. The core device in the single-fiber bidirectional optical module is a 45° beam splitter. The light source irradiation surface of the beam splitter is coated with an anti-reflection film, and the reflective surface is coated with a reflective film. The composition and principle of the demultiplexer".