TCF-142 converters are used to extend serial transmission up to 5 km (TCF-142-M with multi-mode fiber) or up to 40 km (TCF-142-S with single-mode fiber). Moxa's industrial-grade serial-to-fiber optic converters can convert RS-232/422/485 to optical fiber. Moxa RS-232/422/485 to Fiber Optic MM Extender with ST Connectors, Ring support, 12 - 48Vdc, 0 to 60°C.