Fiber optic rotation sensor utilizing high birefringence fiber and having reduced intensity type phase errors.

摘要

A fiber optic rotation sensor using birefringent optical fiber (11) includes an uncorrelating element (200, 202), an equalizing element (204) and a polarizer (220) in the common input and output fiber portions (13) of the sensor to reduce or eliminate the intensity type phase errors caused by interference between lightwaves originally in the same polarization mode on entry to the sensor loop (16) that cross couple into another polarization mode. In the preferred embodiment, the uncorrelating element (200, 202) comprises a birefringence modulator (202) and a length (200) of birefringent fiber. The equalizing element (204) comprises a birefringent fiber (11, 13) having a splice (204) at which the axes of birefringence of the spliced portions (206, 208) of the fiber (11, 13) are positioned at 45 DEG relative to each other. The preferred embodiment also advantageously includes a birefringence modulator (60) that introduces a time-varying birefringence into the optical fiber (11) to introduce a deterministic phase error that reduces or eliminates amplitude type phase error caused by coherent interference between field components of light that are orthogonally polarized at the input of the sensor loop (16) and that couple to the same polarization mode within the loop (16).