Method for alignment of proton-exchange LiNbO₃ waveguide and polarization-maintaining pigtail

A new method for alignment of proton-exchange LiNbO₃ waveguide and polarization-maintaining (PM) pigtail is proposed based on broadband lightsource and Polarized-light Interference Effect (PIE). Broadband lightsource and PM fiber for alignment is fused together, and different secondary peaks appear on coherence function due to PIE when broadband light passes through PM fiber and proton-exchange LiNbO₃ waveguide. The alignment angle can be resolved with position and amplitude information of the secondary peaks, and on-line alignment can be implemented with the feedback of this angle.