An Experimental Technique for Aligning a Channel Optical Waveguide with an Optical Fiber Based on Reflections from the Far End of the Waveguide

A method for aligning the waveguide of a photonic integrated circuit and an optical fiber according to reflections from the far end of the waveguide, which was obtained using the optical reflectometry method in the frequency domain, is presented. The reflectometer was designed on the basis of a Michelson interferometer. The measuring arm of the interferometer was a line formed by the optical fiber and the channel waveguide of a photonic integrated circuit (PIC). The PIC with proton-exchange channel LiNbO3 waveguides was polished at an angle of 10°, while the tip with an optical fiber was polished at an angle of 15°. In this study, experiments on the alignment of the optical fiber and the waveguide were performed and analyzed. It is shown that the amplitude of a signal reflected from the far end of the waveguide was determined by the size of the longitudinal and lateral displacements between the fiber and waveguide. The maximum amplitude of the peak was 16 dB. During the experiments, it was found that the accuracy of the alignment method was 4, 1, and 1 μm along the X, Y, and Z axes, respectively.