Proximity sensor

A system for measurement of a distance to a target. Light is emitted from a multi-mode laser and coupled to a sensor assembly. A portion of the light at the sensor assembly is reflected back into the fiber optic cable from which it came. The other portion of the light from the sensor assembly is projected towards the target. Light is reflected from the target and also connected into the optical cable as a target beam. The target beam and the reference beam then are connected through a path of variable length. When the target beam and the reference beam interfere with one another, the path length is determined to be equal to the length to the target.