Abstract

We describe a 2 x 2 fiber optic switch that uses 50/125 pm multimode fibers and operates at 830 nm. The switch employs six polarizing beam splitter devices and switchable electro-optic, half-wave retarders made with two surface-stabilized ferroelectric liquid crystal films. The light at each of the four fibers passes through a gradient index lens that collimates the input light and focuses the output light onto the fiber's core. A beam splitter then separates the unpolarized input light into two orthogonal linearly polarized components, and the switchable retarders control the light's path inside the switch by controlling its polarization. The component beams are recombined at the output by a polarizing beam splitter. The switch exhibits cross talk of -27.6 dB in the bar state and -22.3 dB in the cross state. Insertion loss is 2.1 dB in the bar state and 3.0 dB in the cross state. These values are stable over temperature from 0° to 45°C and then monotonically degrade until the limits of operating temperatures are reached at -20° and near 62°C. The switching time is 50 ps at room temperature when driven by ±15 V. Lifetime testing to the extent of 10⁹ cycles produces no change in characteristics. Although we did not measure it, the signal bandwidth is limited to about 6 GHz by path length differences within the switch.

© 1992 Optical Society of America