FIBER OPTIC ROTATION SENSOR UTILIZING UNPOLARIZED LIGHT

摘要

FIBER OPTIC ROTATION SENSOR UTILIZING UNPOLARIZED LIGHT A fiber optic rotation sensor, employing detection of the Sagnac phase shift, comprises a single mode fiber forming a loop. The rotation sensor utilizes unpolarized light to provide reciprocal operation. The unpolarized light produces incoherent light wave components which are averaged to zero in the detector. Non-rotationally induced phase shifts between coherent components resolve into vectors equal in magnitude and opposite in phase angle so that the non-reciprocal components of these vectors cancel. The rotation sensor is independent of environmental factors when the phase difference between the waves counterpropagating through the loop is an odd multiple of .pi. /2. Accordingly, the sensor includes a phase shifter for biasing such phase difference to .pi. /2 to provide a stable operating point when the loop is at rest. Additional compensating means are included to provide stability during rotation.