The invention disclosed herein relates generally to proximity switches and more particularly to proximity switches that utilize fiber optics. There is a specific need in aircraft to sense the proximity of some movable part of an aircraft such as an aircraft door or a landing gear component. Due to considerations of size, weight and electromagnetic interference it is highly desirable to perform the proximity switch function using a single fiber optic link and a fiber optic switch.
In the past an optical fiber has been used as the communication link to an electrical proximity switch and support electronics. The state of the switch is converted back into a pulse of light which is transmitted back through the optical fiber and detected at the source end of the fiber link. This method requires a high power optical energy source and complicated support electronics at the location of the proximity switch. In addition electrical proximity switches generate electromagnetic interference which is undesirable in an aircraft environment.
Thus a need exists for a passive proximity switch that operates with a single fiber optic link.