The High-Speed FOMs convert the electrical signal into an optical signal for transmission over fibre optic cable, providing extended distance and immunity to environmental interference. At the remote site, the optical signal is converted back into an electrical signal, according to CCITT standards, and amplified to the required level. An adaptive equaliser circuit is incorporated in order to accommodate various distances.
The FOMs comply with CCITT standards G.703, G.921 and G.956. The electrical interface includes circuits for recovering data and clock according to CCITT G.703. The units are available in three versions, depending on the electrical standard used:
FOM-T3 for T3 fibre optic modem: FOM-E3 for E3 fibre optic modem: FOM-STS1 for STS-1 fibre optic modem (see ordering).
LED status indicators and a supervisory port are available for indicating system faults: on both electrical and optical circuits. These include AIS and ERR indicators for the optical interface and LOW and AIS indicators for the electrical interface.
The supervisory port includes two dry contact closures:
1) For minor alarms (AIS in electrical or optical interface)
2) For major alarms (low level at the electrical interface or High Bit Error Rate at the optical interface)
A front panel switch is provided for operating diagnostic loops. Options are available to operate with several grades and sizes of fibre optic cable. Different optical interfaces are available for use with different types of fibre. The High-Speed FOMs are supplied as stand-alone units. Special hardware for mounting one or two units in a 19" rack can be ordered separately.

Ordering Information