How the Bi-directional SFP works over 1 core Fiber?

Single-fiber bidirectional (BiDi) refers to the simultaneous transmission and reception of optical signals in two directions over 1 optical fiber, just like in the road. the vehicles drive on both sides without interference. so Bidi Technology can double the capacity of the existing optical fiber, and much save optical fiber resources.

To achieve simultaneous transmission of optical signals in both directions, two (2) optical wavelengths need to be used in the receiving and sending directions. the Bidi SFP optical module has only one port, but there is the filter inside of the module, so it helps to complete at the same time for the transmission of one wavelength's optical signal and the reception of another wavelength's optical signal. please kindly see the below drawing.

For example, the local end transmits an optical signal of 1310nm while receiving an optical signal of 1550 nm. The opposite end uses the opposite wavelength from the local end. in other words, it transmites 1550nm optical signals and receives 1310 nm optical signals. Therefore, the module must be used in pairs at both ends of the link. The commonly used wavelengths of bidirectional optical modules are 1310 nm/1550nm and 1550 nm/1490 nm.

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