Fiber optic security system for sensing the intrusion of secured locations

A sensor for a security system is disclosed to detect intrusions at one or more predetermined locations wherein each location includes a moveable member which must be moved in order to intrude the location. The system includes a fiber network routed in close proximity to one or more locations. The sensor comprises a sensor housing for being disposed at a location to detect a predetermined movement of the moveable member from a secure position to an unsecured position, and means for mounting the sensor housing in a stationary position at the location without a physical connection to the moveable member. The sensor housing includes a fiber inlet and a fiber outlet, and a fiber chamber for receiving a predetermined sensor fiber of the fiber network being routed through the sensor housing. The sensor has a sensor actuator for engaging the sensor fiber to generate an intrusion signal upon detecting predetermined movement of the moveable member, and causing the intrusion signal to be transmitted along the sensor fiber to a processor whereby the intrusion and location of the intrusion may be determined by the processor. Preferably, the sensor includes a magnetic actuator having a magnetic attraction to the moveable members whose interruption causes activation of the sensor and generation of the intrusion signal.

BACKGROUND OF THE INVENTION

This invention relates to a fiber optic security system and sensor for detecting the intrusion of a secured location and, more particularly, to such a system and sensor wherein each secured location includes a moveable member which secures the location and a fiber optic network routed in close proximity to the location wherein the sensor senses movement of the moveable member to an unsecured position, and the system detects the occurrence and location of the intrusion.

With the increase in terrorist events needed to be prevented in the United States, the need for effective security systems to sense intrusion into secured areas has greatly increased. In particular, a security system for the protection of a vast system of underground utilities accessed by manholes with removeable covers is needed. A highly effective system to detect entrance into these underground spaces and utilities is needed in order to protect against vandalization and terrorist activities within these spaces and the spaces to which these underground utilities lead. Heretofore, it has been known to use fiber optic sensors to detect theft of articles, intrusion into protected areas, as well as a variety of other purposes.

For example, U.S. Pat. No. 4,369,437 discloses a security and alarm apparatus to detect movement of a cover for a fill pipe leading to an underground fuel tank wherein an alarm signal is transmitted if the cover is disturbed. However, the system does not use fiber optics, requires electrical power at the location, and is generally not suited for a wide area security system.

U.S. Pat. No. 5,055,827 discloses an fiber optic security system to prevent the theft of appliances located in a network of computers, terminals, and associated peripheral devices. When one of the appliances is moved, light attenuation of a fiber cable results in a signal being generated. However, this system requires physical connection of the optic fiber to the appliance and the system is not suitable for detecting events in a wide geographical area.

U.S. Pat. No. 5,434,557 discloses an intrusion detection system having at least one optical cable which is usually part of a fence. When the intruder exerts force on the fence, the movement actuates a mechanical device exerting force on the cable which is detected and actuates an alarm. Here again, the system requires physical connection to the moveable part of the fence and the fiber optic cable requires electrical power at the location, and is generally not suitable for wide geographical areas.

U.S. Pat. No. 5,594,239 discloses a measuring system for monitoring buildings, train sections, or the like, consisting of a beam wave guide bending sensor. Basically, the system utilizes the deflection of a beam wave length to detect movement of the building structure.

U.S. Pat. No. 4,814,562 discloses a pressure sensor which utilizes pressure on a fiber optic in order to measure pressure.

U.S. Pat. No. 5,592,149 discloses a security fence which utilized an optical wire woven into the fence material whereupon movement of the fencing by an intruder causes the fiber wire to move and actuate an alarm signal. Once again physical connection is required between the optic fiber and the moveable member. U.S. Pat. No. 4,777,476 discloses another security fence wherein the optic fiber is physically connected to the moveable member to detect movement of a moveable member and intrusion to generate an alarm. U.S. Pat. No. 4,829,286 discloses yet another security fence requiring physical connection of the optic fiber to a moveable member in order to generate a signal caused by an intruder moving the fiber optic. U.S. Pat. No. 5,049,855 discloses a security screen system wherein an optical fiber is woven into the screen mesh and distortion of the screen material by an intruder causes an alarm signal.

Not only do the above security systems and sensors require a physical connection between the optic fiber and the moveable member, but the systems require electrical power at the location sought to be protected making them wholly unsuitable for many security applications, including wide geographical area systems. More importantly, no provision is made for identifying the location of an intrusion event where large numbers of sensors are utilized.

Accordingly, an object of the present invention is to provide a security system for detecting intrusion at a secured location using a fiber optic network and sensor by which the occurrence and location of an intrusion even can be reliably determined.

Another object of the present invention is to provide a security system for detecting an intrusion at any one of a plurality of secured locations using an fiber optic network in close proximity to the locations wherein the actuation of a sensor by an intruder and the exact location of the sensor and the intrusion can be determined at any one of the locations.

Another object of the present invention is to provide a sensor for a security system which can be utilized with an fiber optic network requiring no electrical power and requiring no physical connection to a moveable member having a secured position in order to detect movement of the moveable member to an unsecured position.

Yet another object of the invention is to provide a security system using a pre-existing fiber optic network which carries voice and/or data transmissions wherein a fiber of the network may be connected to a series of sensors and to an optical reflectometer so that the occurrence and location of an intrusion may be determined.

SUMMARY OF THE INVENTION

The above objectives are accomplished according to the present invention by providing a security system for detecting intrusion at a plurality of predetermined locations using a fiber network composed of a plurality of optic fibers routed in close proximity to the locations. The system comprises sensors disposed at the locations contacting an optic fiber from the fiber network selected as a sensor fiber for detecting physical intrusions at the locations and generating intrusion signals when one or more sensors are activated. A processor in communication with the sensor fiber receives the intrusion signals from the activated sensors and determines the location of each activated sensor. A communication output is operatively associated with the processor for communicating identification of each activated sensor and the location of each activated sensor. Preferably, the locations include a moveable member which must be moved in order to intrude into the location, and the sensors are disposed adjacent to the moveable members in a non-contacting manner. The sensors detect a predetermined movement of the moveable members from a secured position to an unsecured position whereby intrusion signals are generated without physical connection between the sensors and the moveable members. Advantageously, the sensors may include magnetic attractions between the sensors and the moveable members whose interruption causes activation of the sensors and generation of the intrusion signals. In the illustrated embodiment, the sensors include a reciprocating sensor actuator having a deactivated position and an activated position. The sensor actuator engages the sensor fiber when the moveable members are in an unsecured position causing sensor activation and the intrusion signal to be generated. The moveable sensor actuator forms a predetermined bend in the sensor fiber when activated to produce a characteristic intrusion signal that is readily recognizable by the processor to reliably detect a sensor activation and sensor location. In an advantageous aspect, the sensor actuator includes a first contoured abutment with a prescribed contour for engaging the sensor fiber, producing a predetermined bend in the sensor fiber upon activation of the sensor. In the illustrated embodiment, the sensor includes a sensor housing having a fiber chamber. The sensor fiber is routed through the fiber chamber with a natural bend producing no attenuation in the sensor fiber when the sensor is deactivated. The sensor actuator engages the natural bend of the sensor fiber to form the predetermined bend in the sensor fiber when the sensor is activated causing the characteristic attenuation in the sensor fiber and generation of the intrusion signal. The fiber chamber includes a fiber receiving space defined between the first contoured abutment of the sensor actuator and a second contoured abutment through which the sensor fiber passes. The second contoured abutment engages the sensor fiber to produce the natural bend when the sensor is deactivated, and the first contoured abutment engages the sensor fiber to produce the predetermined bend when the sensor is activated. Preferably, the first and second contoured abutments are carried by the movable actuator. A biasing element connected between the movable actuator and the sensor housing forces the first contoured abutment to engage the sensor fiber when the sensor is activated. The sensor housing includes a fiber inlet and a fiber outlet so that the sensor fiber is routed through the inlet, through the fiber chamber where the sensor fiber assumes the natural bend, and through the fiber outlet.

In accordance with a method for detecting intrusion into a protected location using a fiber network connected to an optical reflectometer processor, the method comprises providing a sensor for detecting a predetermined movement of a moveable member which must be moved in order to intrude into the location. Next; a connection between a fiber of the fiber network and the sensor is made so that a predetermined movement of the moveable member causes the sensor to be activated and to generate an intrusion signal which is transmitted to the reflectometer device through the fiber. Next, the method includes processing the intrusion signal to determine the location of the sensor and hense, the intrusion. Advantageously, the method includes using existing utility fiber networks which carry voice and data signals, and providing connection to a fiber of the fiber network as a sensor fiber for generating and transmitting the intrusion signal. The connection between the fiber and the sensor is made without making a physical connection between the fiber and the moveable member. The method includes providing a sensor having a moveable actuator which contacts the fiber causing generation of the intrusion signal in response to movement of the moveable member to the unsecured position; and providing a magnetic attraction between the moveable actuator and the moveable member which is broken when the moveable member is moved to an unsecured position. Advantageously, the method includes arranging the fiber to have a natural bend producing generally no attenuation when said sensor is deactivated, and deforming said natural bend to a predetermined bend when the sensor is activated to generate the intrusion signal having a discernible characteristic wave form resulting from the bend.

DESCRIPTION OF A PREFERRED EMBODIMENT

Referring now to the drawings, the invention will now be described in more detail.

As can best be seen inFIG. 1, an optical fiber security system, designated generally as A, is illustrated. The security system includes a remote processor, designated generally as10, for processing an intrusion signal to determine the occurrence and location of the intrusion. The processor may, for example, include an optical time domain reflectometer (OTDR)12of the type routinely utilized to monitor maintenance of fiber optic network systems. Typically, the OTDR is used to sense a fiber breakage, water seepage, irregular bends, or other defects in one or more optical fibers of the fiber network along the routing path of the network. For example, in large municipalities it is not uncommon for there to be 1,000 miles of fibers in an optical fiber network. However, as opposed to these conventional uses, an expedient of the present invention is to utilize the OTDR to detect the occurrence and exact location of an individual attempting an intrusion into a secured location. In the illustrated embodiment ofFIG. 1, the OTDR is connected to two fiber optic networks15aand15b. Each network includes a plurality of secured locations comprised of a series of utility manholes16. A transponder17may be located at the end of each fiber optic network. The manholes include manhole manifolds18, and manifold covers20which cover and secure the manholes. For purposes of illustration, and not limitation, three manholes16a,16b, and16cof network15awill be discussed to illustrate the invention. Of course, any number of manholes as are disposed in close proximity to the fiber optic network may be placed in series in the security system. Typically, fiber optic networks run through the underground tunnels to which access is provided through the manholes. Of course, many other type of utility cables, channels, water and sewage are typically routed through the underground tunnels.

As can best be seen inFIGS. 2,3A, and3B, a sensor, designated generally as24, is attached in a stationary position by means of an adjustable bracket26to an interior sidewall28of each manifold. Each sensor includes a sensor housing30attached to mounting bracket26which, in turn, is mounted to interior sidewall28by means of conventional fasteners32extending through adjustable slots34of bracket26. In this manner, the vertical position of sensor24can be adjusted relative to a top flange20aof manhole cover20so as to be mounted out of contact but closely adjacent to the flange of the manhole cover, for reasons explained more fully below.

FIG. 3Ashows the manhole cover in a secured position wherein the sensor is deactivated.FIG. 3Bshows the manhole cover moved to an unsecured position wherein the sensor is activated.

As can best be seen inFIGS. 4A and 4B, intrusion sensor housing30includes a fiber entrance38and a fiber exit40. A moveable sensor actuator46is slidably carried within a cutout slide cavity48. A spring50is attached to the sensor actuator at52on one end and to a post54affixed to housing30at an opposite end. In the illustrated embodiment, sensor actuator46includes a magnet56and a first arcuate abutment58made integral with magnet56by means of a clip60. Sensor actuator46also includes a second arcuate abutment62. Arcuate abutments58,62define a fiber receiving space64therebetween. Receiving space64includes an entrance trumpet66, an outlet trumpet68, and a throat70therebetween. A fiber14awhich is removed from the fiber network, is routed through the sensor and the fiber receiving space. Preferably the sheath of the fiber is removed so that only the optic fiber14ais routed through the receiving space of the sensor actuator. The sensor is illustrated in a deactivated position inFIG. 4Awherein fiber14ais routed through the housing inlet, fiber receiving space64, and the fiber outlet. It can be seen that the fiber passing through the fiber receiving space assumes a natural or circular curve14bover a major portion within the sensor. In the deactivated position moveable sensor actuator46is maintained as shown inFIG. 4Aby the magnetic force of attraction between magnet56and manhole cover20in its secured position. When the manhole cover is moved to the unsecured position, a predetermined distance from magnet56, the magnetic attraction is broken and sensor actuator46moves vertically to place a predetermined bend72in the fiber14a, as can best be seen inFIG. 4B. In order that a predetermined and characteristic bend is placed in the fiber that will emit a uniform signal anytime the sensor is activated, first arcuate abutment58includes a contour at74. Preferably contour74is provided in the form of a tangential flat surface that creates a controlled radius in the bend72of the fiber that causes a characteristic intrusion signal shape to be received by the OTR device and displayed, e.g., see signal90aatFIG. 5. By providing a consistent and uniform fiber bend and attenuation, the intrusion signal can be detected and recognized on the display screen of the OTR device in a reliable manner.

In the preferred embodiment, actuator46includes magnet56which is maintained in the deactivated position by proximity of sensor24to the metal flange of manhole cover20. Spring50is tensioned when moveable actuator46is in the deactivated position ofFIG. 4A. When the magnetic force is broken, the spring tension pulls the actuator downwards to place predetermined bend72in optic fiber14a. In the event that a nonmetallic material is used for the manhole manifold and cover, a metallic material insert may be placed in an area of the manhole cover which will maintain actuator46in a retracted, deactivated position ofFIG. 4A. The manhole cover has a secure position fitted within the top opening of the manifold, and an unsecured position when it is moved from the secured position which is sufficient to break the magnetic attraction. In order to eliminate false detections, sensor24is mounted a sufficient distance from the manhole cover, e.g., one-half inch, so that fluttering of the cover by traffic, etc., does not break the magnetic attraction between actuator46and the cover. However, when the cover is moved a sufficient, predetermined distance to an unsecured position which indicates an intrusion, the magnetic attraction is broken and sensor actuator46moves to the activated position ofFIG. 4Bwhereupon optic fiber14ais deflected changing its reflection properties and attenuation. Variations on the sensor actuator and types of sensors, may be had, although it is advantageous that there be no mechanical or direct connection between the optic signal wire used in the sensor and the moveable member needed to be moved by an intruder, and that no electrical power be required for the sensor operation.

When a characteristic intrusion signal is produced, such as90a,90b, or90c, the OTR device measures the distance to the signal, or signals. The sensor locations are mapped by the processor system so that a display or printout of the sensor and its exact geographical location is produced. In this manner, the exact point of the intrusion is determined so that a timely response may be made at the location of the intrusion.

As can best be seen inFIG. 1, OTDR is connected to a computer system C having a computer processor80connected to a monitor82with a display screen84. A normal OTDR signal86is transmitted from the OTDR to computer processor80, and displayed on monitor82. Conventional input devices, keyboard88, and mouse89, may be provided for operating computer system C. Of course, other means of displaying the OTDR signal may be used, such as a dedicated display device.

Referring toFIGS. 5 through 8, the operation of the system and identification of activated sensors will now be discussed.FIG. 5illustrates display screen84of monitor82displaying a normal signal86which is received in the absence of an OTDR intrusion event, or other fiber disturbance signal. Optic sensor fiber14ais commonly routed through each of sensors24a,24b,24c. As illustrated inFIG. 5, none of the sensors are activated so a normal signal86is displayed on the screen. InFIG. 6, sensor24bis activated, and an OTDR intrusion signal90bis displayed showing that an intrusion event has occurred at sensor24b. Since the location of sensor24bis known and mapped, the location of the intrusion is determinable.FIG. 7shows the graphic display screen60when an instruction event has occurred at both sensor24band24c, as indicated at signal90band90c.

FIG. 8illustrates graphic display of OTDR signals at90a,90b, and90cwhen an intrusion event has occurred at all three sensors24a,24b, and24c. Since the locations of sensors24a,24b,24care predetermined and mapped, the location of the intrusion event is known by knowing which sensor is activated. It is noted that intrusion signals90a,90b, and90chave a characteristic shape predetermined by the shape of bend72created in optic sensor fiber14aby contour74of abutment58. This characteristic signal shape is reliably recognized as an intrusion event signal. Typically, the OTDR will also have other characteristic signals which represent other fiber disturbances and resulting attenuation. For example, a 0.5 db power drop indicates an intrusion, a 1 db power drop indicates water seepage, a 0.3 db power drop indicates an irregular bend, a fiber breakage is represented by a straight spike, etc.

Thus, it can be seen that a highly advantageous construction for a security system and sensor can be had according to the invention where preexisting or new fiber networks can be utilized in close proximity to locations needed to be secured whereby sensors connected in series with an OTDR device can be utilized to determine the occurrence and location of an intrusion anywhere along the fiber optic network. For example, if a municipality has 1,000 miles of fiber optic network routed through tunnels accessible by manholes, each manhole may be provided with a sensor to determine whether it has been moved to an unsecured position. In this manner, the entire network of manholes and fiber optic network, as well as other underground utilities, may be secured against terrorists or other acts of invasion, vandalism, etc.