Simultaneous two-way communications through a single fiber with solid-state lasers as source are described. A system was designed to use the same optical subsystem for transmitting as for receiving at each of the two communicating stations. A multilayer, single-mode, elliptical fiber capable of preserving the two orthogonally polarized modes of propagation was used as the transmission medium. The multilayer configuration was constructed to confine most of the energy in the fiber core to minimize losses to absorption in the claddings. Separation of the beams was made by a duplexer capable of distinguishing the difference in polarity of the two beams.
Robert Y. Wong,
Sembiam R. Rengarajan,
"Optical Communications With Lasers And Multilayer Elliptical Fibers," Optical Engineering 22(3), 223382 (1 June 1983). https://doi.org/10.1117/12.7973125