Patent CA-1174321-A (CA)
Inventor: PEEK S CHRISTOPHER
IPC: G08B17/103
Filed: 1980-02-29
Granted: 1984-09-11
Abstract: 21,566 CN        ABSTRACT OF THE DISCLOSURE      A fiber optics security system includes closes loop fiber optic link means which transfers energy from a radiant energy source to a radiant energy receiver.  The link means includes a plurality of fiber optic links and a plurality of detectors serially connected.  Cessation of energy to the receiver causes an alarm.  One detector includes an optical transducer spaced a distance from, and in alignment with, a second optical transducer such that light transmitted, through air, is received by the second transducer with insignificant loss so as not to cause cessation of energy to the receiver.  In a water medium, due to its absorption characteristics, light received by the second transducer is so insignificant that energy to the receiver ceases.  The first transducer provides a beam of light along a straight path within a medium having a constant index of refraction to the second transducer spaced therefrom and oriented along the path so as to ordinarily receive the beam of light.  When light passes through media having different indices of refraction at angles other than normal, light is refracted away, whereby energy to the receiver ceases.  The media can be the same substance with different indices of refraction, or it can be of different substances.  The two transducers are so spaced and oriented that the straight path therebetween is both other than horizontal and other than vertical.     Another detector includes optical fiber which is stable at temperatures of up to approximately 135°F but which melts at some temperature above approximately 155°F, thereby providing for fire detection by causing cessation of energy to the receiver.     Still another detector includes a pair of holders for holding a pair of optical fibers in axial alignment with each other.  A bimetallic element is attached to one of the holders so that, when heated, one of the holders 21,566 CN   displaces,  thereby displacing one optical fiber with respect to the other.  The bimetallic element can include a snap action bimetal device for causing displacement to occur at a specific temperature.     Yet another detector includes a first connector for a first optical fiber and a first condensing lens so that light transmitted from the first fiber through the first condensing lens emerges as a narrow radiant energy beam. A second connector holds a second optical fiber and a second condensing lens so that an end of the second fiber is near the focal point of the second lens.  The second connector is in axial alignment with the first so that the received narrow radiant energy beam causes light to be transmitted through the second fiber.  Any opaque object between the two connectors interrupts the beam thereby causing cessation of energy to the receiver.     Still another detector is achieved by coupling one optical fiber to one side of an entrance device, and coupling a second optical fiber to the opposite side thereof in axial alignment with the one optical fiber. Opening of the device causes the respective ends of the fibers to misalign, thereby interrupting energy to the receiver.     The radiant energy source and the radiant energy receiver are in proximity to each other.