The interface of optical module is mainly divided into single-fiber bidirectional BiDi, dual-fiber bidirectional (Deplux) and other types. In WDM system, the line transmission method mainly uses single-fiber unidirectional and single-fiber bidirectional.

Single-fiber bidirectional, also known as BiDi (Bidirectional), refers to an optical fiber can simultaneously send and receive optical signals in two directions. Conventional fiber optic transmission is single-fiber unidirectional, to achieve bi-directional communication requires two optical fibers, compared to the BiDi technology requires only one optical fiber can be, that is, the existing optical fiber transmission capacity doubled, thus saving the fiber optic resources.

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However, for BiDi optical modules, the optical modules at both ends of the link must be used in pairs. While general optical modules have two ports for transmission and reception, BiDi optical modules have only one port, which is filtered by the filter in the optical module, and simultaneously accomplishes the transmission of TX optical signals and the reception of RX optical signals or vice versa.

Dual-fiber optical modules have only one wavelength, usually 850nm, 1310nm, 1550nm and so on. Single-fiber optical modules have two different wavelengths, commonly the following wavelengths:

BiDi optical modules are compact, optical transceiver device consists of BOSA, components contain detectors, adapters, BOSA combines the two together, compared to TOSA, ROSA components more filters and bases.BiDi optical modules currently support rates of 155M , 1.25G, 10G, 16G, 25G, 40G, 100G and so on.

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As BiDi optical modules use the wavelength does not produce a large dispersion cost, transmission indicators and dual-fiber bidirectional optical modules and no other differences in cost and has a clear advantage, without increasing the maintenance and management, so the fiber optic direct connection is generally used in a single-fiber bi-directional program. At the level of optical modules, BiDi optical modules and color optical modules are to a certain extent to improve fiber utilization, for users, is also a good choice to save costs.

Additional Learning Hub Resources 

Single-mode fiber vs Multi-mode fiber how to choose? 

In what ways does BiDi fiber enhance broadband transmission? 

10G BIDI SFP+ Optical Modules Wiki 

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