TL-FC111B-20 is a media converter, providing RJ-45 port and 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. TL-FC111B-20 adopts WDM (wavelength division multiplexing) technology, helping send and receive data at a distance of up to 20 km (12.4 miles) over only one fiber, which saves half of the cable deployment cost for customers. TL-FC111B-20 transmits data at 1310 nm wavelength and receives data at 1550 nm wavelength on optical fiber. The TL-FC111A-20 works in the other end as a pair by receiving data at a wavelength 1310 nm and sending data at wavelength 1550 nm.