FIBER OPTIC ROTATION SENSOR UTILIZING HIGH BIREFRINGENCE FIBER AND HAVING REDUCED INTENSITY TYPE PHASE ERRORS

摘要

FIBER OPTIC ROTATION SENSOR UTILIZING HIGH BIREFRINGENCEFIBER AND HAVING REDUCED INTENSITY TYPE PHASE ERRORSAbstract of the DisclosureA fiber optic rotation sensor using birefringentoptical fiber includes an uncorrelating element, anequalizing element and a polarizer in the common input andoutput fiber portions of the sensor to reduce or eliminatethe intensity type phase errors caused by interferencebetween lightwaves originally in the same polarization modeon entry to the sensor loop that cross couple into anotherpolarization mode. In the preferred embodiment, theuncorrelating element comprises a birefringence modulatorand a length of birefringent fiber. The equalizing elementcomprises a birefringent fiber having a splice at which theaxes of birefringence of the spliced portions of the fiberare positioned at 45° relative to each other. Thepreferred embodiment also advantageously includes abirefringence modulator that introduces a time-varyingbirefringence into the optical fiber to introduce adeterministic phase error that reduces or eliminatesamplitude type phase error caused by coherent interferencebetween field components of light that are orthogonallypolarized at the input of the sensor loop and that coupleto the same polarization mode within the loop.