When the measurable difference between two equal fiber path lengths in a fiber coupler could not exceed 5 micrometers, researchers in the Center for Photonics Technology designed a new polishing technique.
Bradley Fellow Evan Lally and undergraduate Tyler Shillig have been working on a special white-light interferometry technique to monitor the exact optical path length difference between two coupler arms. The two lengths of fiber are placed in a precision adjustable polishing jig, and their lengths are monitored as the fiber tips are ground down.
The team reports they expect their polishing system to achieve 0.1 micron path length equalization.
Having a fiber coupler with exactly equal length output arms is critical to the operation of a system they are developing to image small rock and sand particles in asphalt. The project is sponsored by the National Cooperative Highway Research Program.