What This Product Does TL-FC311B-20 is a gigabit media converter, providing a gigabit RJ-45 port and a gigabit SC fiber port, which can convert between electrical and optical signals. And long-distance data transmission through optical fiber can be applied to commercial scenarios such as park security monitoring and wireless networking.How This Product Works TL-FC311B-20 adopts WDM (wavelength division multiplexing) technology, helping send and receive data at a distance of up to 20 km with only a single mode fiber, which saves half of the cable deployment cost for customers. TL-FC311B-20 transmits data at 1310 nm wavelength and receives data at 1550 nm wavelength on optical fiber. Therefore, the terminal device used in conjunction with the TL-FC311B-20 should send data at a wavelength of 1550 nm and receive data at a wavelength of 1310 nm. TP-Link another media converter TL-FC311A-20 is one of the products that can cooperate with TL-FC311B-20.Other Features Besides, this media converter can be used as a standalone device (no rack required) or used with TP-Link's TL-FC1420 rack for auto MDI/MDI-X in TX port in which duplex mode is automatically negotiated.