YUCOO-RS422-01 Fiber optical modem is equipped with a multiple interface circuit that can handle RS-232, or RS-422/485 serial interfaces and multi-mode or single- mode fiber. YUCOO-RS422-01 Fiber Optical modem converters are used to extend serial transmission distance up to 2 km (multi-mode fiber) or up to 20 km (single- mode fiber). Note that the RS-232 and RS-422/485 interfaces cannot be used on the same YUCOO-277 Fiber optical modem at the same time to convert to fiber. Auto Baud Rate Detection.