What This Product Does TL-FC111B-20 is a 100M media converter, providing a 100M RJ-45 port and a 100M 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-FC111B-20 adopts WDM (wavelength division multiplexing) technology, helping send and receive data at a distance of up to 20km (12.4 miles) over only one fiber, which saves half of the cable deployment cost for customers. TL-FC111B-20 transmits data at 1310nm wavelength and receives data at 1550nm wavelength on optical fiber. The TL-FC111A-20 works in the other end as a pair by receiving data at a wavelength 1310nm and sending data at wavelength 1550nm. 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.