In the rotation rate measuring instrument, two component beams derived from a light beam produced by a laser circulate around a coiled optical waveguide (radius R, length L) in opposite directions. From the phase difference between the two component beams due to the Sagnac effect, the rotation rate is...http://www.google.ca/patents/US4591269?utm_source=gb-gplus-sharePatent US4591269 - Rotation rate measuring instrument
