Black Box MD640A-ST-R2 Multimode FOM Fiber Modem

The Black Box MD640A-ST-R2 Multimode FOM Fiber Modem is a compact RS-232 fiber-optic modem designed for point-to-point serial links over a single 62.5-µm multimode fiber. The fiber interface on this ST-series model uses an ST multimode connector and pairs with standard bulk multimode fiber assemblies such as EFN1004 or EFN1006. On the RS-232 side, the device connects to DCE equipment with a cross-pinned RS-232 cable of the null-modem type, enabling direct extension of RS-232 signals over fiber without electrical interference on the link. Powered from 120 V AC, this modem is part of Black Box’s MultiMode Fiber Optic Modem (FOM) family and is designed for short-range optical transmission, suitable for laboratory, automation, and instrumentation environments where a simple, reliable fiber link is preferred for RS-232 communication.