A novel fiber phase-shifter is proposed. It is based on the birefringence effect induced when a polarization-maintaining optical fiber is deformed periodically. The relative phase delay between two fiber modes is altered by fiber axis perturbations to produce a light beam deflection of the far-field pattern by 20 degrees.
"Birefringence-Controlled Phase-Shifter", Proc. SPIE 1175, Coherent Lightwave Communications: Fourth in a Series, (5 February 1990); doi: 10.1117/12.963265; https://doi.org/10.1117/12.963265