Macrodyne, Inc. macrodyne, inc.

 1 Fairchild Square  s  PO Box 376  s  Clifton Park, New York  12065  USA



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Fiber Optic Data Communications

  Macrodyne FOM100 Fiber Optic Modem
FOM100 Fiber Optic Modem

The FOM100 is a small, inexpensive fiber optic transmitter/receiver. It features a complete RS-232 port as well as high speed TTL/ RS-422/ RS-423 data transmit and receive.  It is capable of data rates from DC to 5M baud.  A pair of these units allow most RS-232C cable links to be replaced and extended with a duplex fiber optic cable.  The normal 50-foot RS-232 limit may be extended to 1.2 miles (2 km).  Fiber optic data communications provide complete EMI / RFI rejection, isolation, elimination of ground loops, and reduced error rates.  Data security is enhanced by almost nonexistent electromagnetic emissions.  A unique multipoint capability allows local area networks to be formed with the isolation and data security of a fiber optic highway.

The FOM100 is packaged in a small rugged aluminum enclosure.  The RS-232 connection is through a female EIA 25-pin connector.  The fiber optic connections are through SMA connectors.  Three diagnostic LED indicators are provided.  The TTL port combined with the RS-232 port may be interfaced to RS-422 / 423 ports.  Fiber optic cables may be ordered with connectors factory installed.

Recommended Cables

The FOM100 fiber optic transmitter is optimized for launching power into fiber sizes 62.5 / 125, 100 / 140, and 200um plastic coated silica (PCS).

Multipoint Operation

Local area networks are easily implemented with the FOM100.  When a talker unit raises Request to Send (RTS), its data is communicated to all other devices on a common loop.  Data returns to the sending unit, verifying physical integrity of the loop.  Alternately, if pin 16 is strapped to pin 17, echo will be inhibited.  Units may be ordered with this connection made internally.  For multipoint installations, it is important that power be applied to all FOM100s.  For small networks it will likely be acceptable to power each unit from a local source.  Larger networks may benefit from routing a common low voltage power bus along with the fiber optic cable.  An AC bus with isolation transformers at each unit will preserve system resistance to electrical disturbances.  The wide low voltage AC and DC tolerance makes voltage drop on this bus easily accommodated .



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