Fiber Fabry–Perot interferometers with very low polarization sensitivity

The sensitivity to input polarization in long-cavity (1 cm to 5 m) and high-finesse (~ 100) fiber Fabry-Perot interferometers (FFPI's) is reduced from greater than 20 dB to between 0.2 and 0.6 dB in passband amplitude variation by the use of very-low-birefringence fibers. Furthermore the scanning FFPI's could allow very-high-resolution measurement of polarization-mode dispersion in short-length low-birefringence fibers.