FIBER OPTICS SYSTEM WITH SELF TEST CAPABILITY

摘要

A fire detection system incorporating fiber optics and having a selectively energizable light source for applying light pulses to a fiber optics path and a one way light transmitting element, such as a dichroic mirror, at the remote end of the fiber optics path for reflecting the pulses back to the detection portion of the system, thus providing a Built In Test Equipment (BITE) test capability in the system. Instead of a dichroic mirror, a bandpass filter may be used as the light transmitting member. The bandpass filter is selected to transmit light with wavelengths in the range from about 1.3 to 1.5 microns, in which case the light source is a light emitting diode (LED) emitting light at a wavelength of approximately 0.9 microns. The fiber optics path includes a branch which is coupled to the light source. This branch may comprise one fiber of a multi-fiber bundle or it may be an auxiliary fiber of a commercially available fiber optics combiner. An overall system incorporates a plurality of these individual fire detection arrangements in conjunction with a BITE control stage and associated fire alarm. Any detected fire activates the fire alarm. However, the same fire detection signal, when the system is operated in the BITE test mode, is used by the BITE apparatus to detect failures in the system and identify the portion of the system experiencing the failure.