The OPTONET system monitors the position of up to 30 ON/OFF fiber optic limit switches. It is
based on Optical Time Domain Reflectometry : an optical pulse emitted by a pulsed laser diode is
splitted between the sensors by an optical star coupler. Delay lines are inserted on the optical
lines in order to separate the pulses backreflected by the switches. This paper establishes the
main characteristics of the OPTONET system from an user point of view.
These characteristics depend on the optical fiber properties and the time domain multiplexing
method. The well known optical fiber properties lead to high EMI immunity, lightweight,
galvanic isolation, in particular while the time domain multiplexing leads to saving in cable,
weight and cost, and it requires only the use of a single source and detector. Moreover, various
limit fiber optic switches may be connected to the network since the OPTONET system operates
properly with any reflective switches. The number of sensors which may be monitored by the
system will be examined.
The OPTONET system is presently used on several industrial plants and these applications will
Finally, the future developments of the system will be presented and discussed.