Metrological Traceability of High Polarization Extinction Ratio (PER) Based on Precision Coaxial Rotating Polarization-Maintaining Fiber

This article proposes a metrological traceability method for polarization extinction ratio (PER) ranging from 0 up to 70 dB, while the common method is limited to 50 dB. A precision alignment coupling point is designed and manufactured using two polarization-maintaining fibers (PMFs). By rotating one of the PMFs to change the axis-alignment angle and to control the distribution of light energy in the fast and slow axis, a traceability chain from the PER to the rotation angle is established. With extremely low-stress clamping of the PMF, 5-D precision adjustment of the fiber position, and precision coaxial rotation in the order of arc seconds, accurate and controllable generation of any PER in the range of 0–70 dB can be achieved. A high PER traceability system is designed and built, which is successfully used in the traceability of PER to the angle of circumference. The expanded uncertainty ( $k = 2$ ) in the ranges of 0–30 dB, 30–50 dB, and 50–70 dB is 0.01, 0.06, and 1.20 dB, respectively. Controlled generation of high PER (50–70 dB) with metrological traceability is realized for the first time as far as we know.