o In optical modules, "core" refers to the light-transmitting channel in the fiber. A 1-core module uses a single fiber core for data transmission, while a 2-core module uses two cores. They are easier to set up and give steady communication. A. Single fiber module also called BiDi transceiver or WDM module. BIDI module only has 1 port, wave filtering through the filter of module, and finished the transmitting of 1310nm optical signal. In today's communication field, single-core optical fibre and dual-core optical fibre are like remarkable stars, the powerful technology behind them and the disruptive impact on the communication industry deserve everyone's attention and discussion.