Imperfect quarter-waveplate compensation in Sagnac interferometer-type current sensors

We analyze scale factor errors associated with integrating imperfect quarter-waveplates into loop and in-line Sagnac interferometer fiber-optic current sensors. We show that relatively large imperfections in the quarter-waveplates can be tolerated in the loop version when the birefringence axes of the two quarter-waveplates are oriented 45/spl deg/ with respect to each other. For the in-line version, we demonstrate an electronic signal processing scheme that desensitizes the scale factor to imperfections in the quarter-waveplate.