Optical switches using ferroelectric liquid crystals

DETAILED DESCRIPTION The invention comprises an optical switch wherein an input optical fiber directs light onto a first polarization means that polarizes the incoming light and directs it to a ferroelectric liquid crystal (FLC) which is preferably a smectic phase liquid crystal.
In the preferred embodiment of the invention, the ferroelectric liquid crystal receives the polarized light at normal incidence and selectively changes the polarization state of the light received.
A second polarization means receives the light from the ferroelectric liquid crystal and directs it to output optic fibers according to its polarization state.
Control of the ferroelectric liquid crystal allows preselection of the polarization state of the output light which is thereby directed to a particular output path according to its polarization state.
In a preferred embodiment of the invention the second polarization means comprises a polarizing beam splitter that selectively directs the light from the ferroelectric liquid crystal (FLC) amongst output optic fibers.
In the preferred embodiment of the invention, the FLC further comprises electrodes for changing the optical rotary power of the crystal in order to select the output polarization state of the optic signals.
Further, the FLC selectively rotates polarized light between the s and p states and is bi-stable.
Specifically, the bi-stable crystal will continue to rotate light according to a previous selection until the electrodes are activated to change the selection.
Another aspect of a preferred embodiment of the invention comprises the use of input optic fibers having a collimating lens for collimating light directed into the FLC.
Further, output optic fibers are provided with a lens for focusing the collimated light, from the FLC, onto the core of the selected output fiber.
A preferred embodiment of the optical switch comprises a 4.
times.
4 non-blocking switch.
This 4.
times.
4 non-blocking switch comprises a polarizer for the four input optical paths, a first liquid crystal cell comprising four addressable pixels, a first light directing layer comprising polarizing beam splitters and right angle mirrors for directing optical signals according to their polarization, a second liquid crystal cell comprising eight addressable pixels, a second light directing layer comprising right angle mirrors and polarizing beam splitters and a third liquid crystal cell comprising eight addressable pixels for selectively changing optical signal polarization