A fiber-coupled heterodyne interferometric displacement sensor

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A fiber-coupled heterodyne interferometric displacement sensor

Nerheim, N.

Space-based interferometers and large segmented reflectors will require precision metrology with nanometer accuracy for active control systems. This paper summarizes an experimental study of an optical heterodyne interferometer with resolution of about 3 nm. Optical signals are carried to and from the interferometer by optical fibers to avoid thermally loading the reflector panels. Heterodyne detection provides far greater precision than does traditional interferometry. A Precision Segmented Reflectors figure maintenance sensor proof-of-concept breadboard based on the concept of an optical heterodyne interferometer was designed, built and tested. The primary goal to demonstrate 30 nm measurement accuracy at a 1 Hz update rate was accomplished. A secondary goal to demonstrate a sensor that would release less than 1 microwatt in the vicinity of the panels was accomplished by transmitting all optical signals to and from the interferometer via optical fiber, thus demonstrating the feasibility of locating the optical source and all electronics at some remote location of the reflector support structure.