Soref R A
Opt Lett. 1979 May 1;4(5):155-7. doi: 10.1364/ol.4.000155.
An adjustable access coupler for multimode fiber-optic networks has been constructed, based on the voltage-tunable total-internal-reflection effect in nematic liquid crystals. Fibers are coupled via graded-index rod lenses at normal incidence to flint-glass prisms in contact with a 6-microm liquid-crystal layer. The achromatic four-port switch has a 1.6-dB optical insertion loss, a tap ratio controllable from -4.6 to -48 dB, a directionality of 44 dB, and an operating voltage of 5 to 20 V rms.
