Both single fiber and dual fiber optical modules can transmit and receive. Since the two communications must be able to transmit and receive. The difference is that a single fiber optical module has only one port. Wavelength division multiplexing (WDM) technology is used to combine different receiving and transmitting wavelengths into a single fiber, filter through the filter in the optical module, and simultaneously complete the transmission of 1310nm optical signals and the reception of 1550nm optical signals, or vice versa. Therefore, the module must be used in pairs (it is impossible to distinguish a fiber with the same transceiver wavelength).
Therefore, a single fiber optical module has a WDM device, and the price is higher than that of a dual fiber optical module. Since the dual fiber optical modules receive and receive on different optical fiber ports, they do not interfere with each other, and therefore do not need WDM, so the wavelengths can be the same. The price is cheaper than that of single fiber, but it requires more fiber resources.
Double fiber optical module and single fiber optical module actually have the same effect, the only difference is that customers can choose single fiber or double fiber according to their own needs.
Single fiber optical module is more expensive, but it can save a fiber resource, which is a better choice for users with insufficient fiber resources.
The dual fiber optical module is relatively cheap, but it needs to use one more fiber. If the fiber resources are sufficient, you can choose the dual fiber optical module.