Patent ID: 7551813

Claim:
A bi-directional fiber-optic on/off switch comprising: a bending device having a first cylindrical rod and a second cylindrical rod, wherein said first rod is the stationary one and said second rod has ability to be linearly shifted from a first position to a second position so extending the distance between said rods; a length of single-mode optic fiber having input and output ends and freely coiled as a multi-turn circular winding around said first rod and said second rod that is in said first position, which is the closest to said first rod; so, said winding does not attenuate a light signal passing said winding; a first fiber-optic connector being optically coupled to said input end and a second fiber-optic connector being optically coupled to said output end; a mechanical actuator, which, when said actuator is activated, moves said second rod from said first position to said second position so extending the distance between said rods and causing said winding to shift its shape from circular to elliptical one, wherein said shape shifting induces high attenuation of said light signal passing said winding so completely terminating transmission of said signal; wherein the improvement comprises: said length of a single-mode optical fiber coiled as a circular multi-turn winding, wherein, to prevent said coil from mechanical fatigue and provide open/close range of switch attenuation from 1 to 50 dB, diameter of said coil exceeds 10 mm; and diameter of said rods is in a range from 1 mm to 3 mm; said bending device modified to use flexibility of cylindrical spring mandrel instead of utilization of the natural flexure of said optic fiber, wherein said bending device additionally comprises a cylindrical spring mandrel mounted on said rods and having a circular shape when said mechanical actuator is not activated; and said winding is reeled and fixed on cylindrical surface of said mandrel; said mechanical actuator, to make the switch safe in underwater, fire and explosive hazardous environments, comprises—an air cylinder powered by compressed gases that do not support burning processes.