Four-port switches which operate independently of the polarization state of incident light are necessary for use with optical fibers which do not preserve polarization. We will review the present state of development of such a switch in Ti-diffused LiNb03 and the progress of end-fire coupling experiments between the switch and single mode optical fibers. Likely applications of such a switch in future optical fiber systems will be discussed.
W. K. Burns,
"Polarization-Independent Switches For Use With Single-Mode Optical Fibers", Proc. SPIE 0139, Guided Wave Optical Systems and Devices I, (13 July 1978); doi: 10.1117/12.956263; https://doi.org/10.1117/12.956263