Amazon.com: Primeda RS485 Data Extenders -1 Bidirectional RS485 to Fiber Optic up to 20Km(12.4mi) | Transmitter and Receiver | for Access Control System : Electronics
GM168MM-F2 Serial To Fiber Converter RS485/422/232 Fiber Modem MM Duplex 2km
RS485 / RS422 / RS232 To SM Fiber Optic Converter
Serial Data RS-232 & RS-485/422 | RLH Industries, Inc.