Abstract: A leak in the membrane of a generally horizontal roof support deck includes dividing the membrane into separate zones and locating a sensor to detect moisture underneath the membrane. A unique digital code address is assigned to sensor where inputs of the sensors are connected to a single power and signaling cable system using a daisy chain. The serial bus controller is to interrogate each of the sensor devices using the address to identify zones where moisture is detected. A transmitting antenna is provided at each sensor which is switched on when moisture is detected for detecting of the sensor from above the membrane by a utility locate device to confirm the location of the sensor.

Abstract: A leak in the membrane of a generally horizontal roof support deck includes dividing the membrane into separate zones and locating a sensor to detect moisture underneath the membrane. A movable scanning device carried by a worker has a power supply antenna for supplying power by an electromagnetic wave to the sensor and the worker moves the scanning device to selected ones of the zones. At each selected zone the power supply antenna activates the sensor in the zone and the sensor to emits signals related to the moisture underneath the membrane as detected by the sensor device which are detected and recorded at the mobile scanning device.

Abstract: A leak in the membrane of a generally horizontal roof support deck includes dividing the membrane into separate zones and locating a sensor to detect moisture underneath the membrane. A unique digital code address is assigned to sensor where inputs of the sensors are connected to a single power and signaling cable system using a daisy chain. The serial bus controller is to interrogate each of the sensor devices using the address to identify zones where moisture is detected. A transmitting antenna is provided at each sensor which is switched on when moisture is detected for detecting of the sensor from above the membrane by a utility locate device to confirm the location of the sensor.

Abstract: Leaks in a roof membrane are detected in plurality of separate zones arranged in rows and columns. By applying to the roof in a location underneath the membrane and on top of the deck in each zone at least one length of a moisture detection sensor comprising a substrate carrying two parallel conductors on one surface of the substrate detecting changes in resistance between the conductors so as to detect moisture permeating into the respective zone. The moisture detecting sensors are separate in each zone so as to detect changes in resistance in the respective zone independent of any changes in resistance in other zones so that the system can detect within the rows and columns any zone where changes in resistance occur. In order to detect across the zone, the sensor is applied in a two dimensional pattern for example by two lengths at right angles.

Abstract: A leak in an electrically conductive membrane attached on top of a horizontal roof deck is located by a manually operable carriage which is swept over the upper surface of the membrane on the roof deck. A measuring and switching circuit generates a voltage having a positive attached to the roof deck and a negative attached to conductive brushes on the carriage. The brushes are arranged to form an outer peripheral contact with an inner contact inside the outer contact. There is provided a diode switched into the sensing circuit from the inner conductive brushes so as to reduce the voltage across the deck and the inner brushes relative to the outer brushes. Thus the presence of a leak is detected by the outer set of conductive brushes at distance from the leak and by the inner conductive brush when directly over the leakage site.

Abstract: A leak in an electrically conductive membrane attached on top of a horizontal roof deck is located by a manually operable carriage which is swept over the upper surface of the membrane on the roof deck. A measuring and switching circuit generates a voltage having a positive attached to the roof deck and a negative attached to conductive brushes on the carriage. The brushes are arranged to form an outer peripheral contact with an inner contact inside the outer contact. There is provided a diode switched into the sensing circuit from the inner conductive brushes so as to reduce the voltage across the deck and the inner brushes relative to the outer brushes. Thus the presence of a leak is detected by the outer set of conductive brushes at distance from the leak and by the inner conductive brush when directly over the leakage site.

Abstract: Leaks in a roof membrane are detected in plurality of separate zones arranged in rows and columns. By applying to the roof in a location underneath the membrane and on top of the deck in each zone at least one length of a moisture detection sensor comprising a substrate carrying two parallel conductors on one surface of the substrate detecting changes in resistance between the conductors so as to detect moisture permeating into the respective zone. The moisture detecting sensors are separate in each zone so as to detect changes in resistance in the respective zone independent of any changes in resistance in other zones so that the system can detect within the rows and columns any zone where changes in resistance occur. In order to detect across the zone, the sensor is applied in a two dimensional pattern for example by two lengths at right angles.

Abstract: A telecommunications multimode optical fiber is secured against intrusion by detecting manipulation of the optical fiber prior to an intrusion event. Pulses are injected using a launch arrangement which generates a narrow spectral width, under-filled, non-uniform mode field power distribution in the multimode optical fiber and Fresnel reflections and Rayleigh backscattering from the pulse are detected at the transmit end to monitor the modal power distribution in the fiber which changes on manipulation of the fiber. The Rayleigh backscattering time sliced data can be stored in a register until an intrusion event is detected. The detection is carried out by a modal power distribution detection system which includes an optical coupler to tap off a portion of the light which contains the higher order signal modes.

Abstract: Intrusion detection for a multimode fiber optic cable uses a light signal launched into the fiber through the low ratio leg of a tap coupler to establish a narrow spectral width, under-filled non-uniform mode field power distribution in the cable. A small portion of the higher order signal modes at the remote end is monitored for transient changes in the mode field power distribution which are characteristic of fiber intrusion to activate an alarm. The active signal of a multimode optical fiber is monitored for both signal degradation and transient power disturbance patterns that could indicate fiber damage or physical intrusion. A translator can be provided in an existing optical fiber system in which the data signals are translated in wavelength and/or launch conditions to optimize the monitoring signals in an otherwise non-optimized system.

Abstract: In a method for secure transmission of data using a quantum key distribution system where individual photons each having a state of polarization are transmitted from the source to the recipient and where the state of polarization the photons is used to provide the series of bits of the encryption key, manipulation of the optical fiber causing movement of a portion of the fiber indicative of an intrusion event is obtained by analyzing changes in time of the number of dropped bits which is those bits which fail to be accurately detected by the recipient since such changes are indicative of changes in polarization of the photons due to handling of the fiber.

Abstract: In a method for secure transmission of data using a quantum key distribution system where individual photons each having a state of polarization are transmitted from the source to the recipient and where the state of polarization the photons is used to provide the series of bits of the encryption key, manipulation of the optical fiber causing movement of a portion of the fiber indicative of an intrusion event is obtained by analyzing changes in time of the number of dropped bits which is those bits which fail to be accurately detected by the recipient since such changes are indicative of changes in polarization of the photons due to handling of the fiber.

Abstract: Intrusion detection of one section only of a multimode fiber uses a light signal launched into the fiber at a location spaced from the source through a single mode fiber to establish a narrow spectral width, under-filled non-uniform mode field power distribution in the fiber. A small portion of the higher order signal modes at the a second location also spaced from the destination is sampled by a tap coupler and monitored for transient changes in the mode field power distribution which are characteristic of intrusion to activate an alarm. The active signal of a multimode optical fiber is monitored for both signal degradation and transient power disturbance patterns that could indicate fiber damage or physical intrusion. A translator can be provided in an existing optical fiber system in which the data signals are translated in wavelength and/or launch conditions to optimize the monitoring signals in an otherwise non-optimized system.

Abstract: Intrusion detection of one section only of a multimode fiber uses a light signal launched into the fiber at a location spaced from the source through a single mode fiber to establish a narrow spectral width, under-filled non-uniform mode field power distribution in the fiber. A small portion of the higher order signal modes at the a second location also spaced from the destination is sampled by a tap coupler and monitored for transient changes in the mode field power distribution which are characteristic of intrusion to activate an alarm. A fiber being used for data transmission can be monitored for intrusion by introducing a monitor wavelength different form that of the data signal. Central to this invention is the use of a bulk optic (commonly referred to as a pass/reflect) wavelength division multiplexer, one which maintains the modal distribution within the fiber.

Abstract: Some or all of the optical fibers of a single-mode or multi-mode cable are monitored for intrusion by transmitting through the fibers a signal which can be analyzed for changes in its characteristics which are indicative of movement as a prelude to an intrusion event. To avoid independent monitors of all of the fibers, in some cases the same light signal is looped through a plurality of the fibers in series by passive jumpers. Switches can be used to disconnect out those fibers which are compromised. As an alternative a plurality of separate monitoring signals can be provided each associated with its own sensor where unique combinations of the signals are transmitted through separate fibers allowing a higher number of fibers to be monitored than the number of signals.

Abstract: A signal which varies over time is monitored to determine an alarm condition, where the sample stream of digital values from an A/D converter is divided in to equal length pieces and a Fourier Transform (FT) algorithm is used to transform each piece of the stream into a three dimensional dataset including frequency domain amplitude, frequency and time. A Frequency Envelope is calculated by taking the maxima over the time dimension for a period of time, leaving a two dimensional frequency domain amplitude vs frequency dataset which is compared with new data arriving to determine the alarm condition for each element of the Frequency Envelope either by applying a constant delta additively or multiplicatively or by using a “leaky bucket” algorithm.

Abstract: An elongated substantially flat four-conductor moisture detection and location sensor is described. The sensor includes four parallel conductors laminated to a dielectric substrate. Two of the conductors are protected by a water pervious dielectric layer and form the water-sensing element. Two other conductors are covered by a water impervious dielectric layer and are used to loop-back one or more of the water-sensing conductors. Precise location of a water leak location is determined by connecting the four conductors to a resistance bridge. The design allows for the connection of a four-conductor cable to extend the monitoring and detection point to a convenient location without loss of location accuracy.

Abstract: An acoustic microphone includes a diaphragm attached to one part a detection coil portion of an optical fiber with another part attached to a fixed base member so that vibrations in the diaphragm cause twisting of parts of the fiber on either side of the coil to change polarization of light from a source of polarized light passing through the fiber. These changes are detected in a sensor defined by a polarizer tuned to be orthogonal to the source so that changes increase the intensity of light from a minimum at the tuned condition. An electronic sensor at an end of the fiber downstream of the detection portion is arranged to detect the changes in the light and convert the changes into an output signal representative of the vibrations monitored. The vibrations are detected only by the detection portion by providing a tuneable polarizer at the entrance to the detection coil and by providing a multimode fiber which is not responsive to the vibrations to carry the light to the sensor.

Abstract: A telecommunications optical fiber is secured against intrusion by detecting manipulation of the optical fiber prior to an intrusion event. This can be used in a non-locating system where the detection end is opposite the transmit end or in a locating system which uses Fresnel reflections and Rayleigh backscattering to the transmit end to detect and then locate the motion. The Rayleigh backscattering time sliced data can be stored in a register until an intrusion event is detected. The detection is carried out by a polarization detection system which includes an optical splitter which is manufactured in simplified form for economic construction. This uses a non-calibrated splitter and less than all four of the Stokes parameters. It can use a polarimeter type function limited to linear and circular polarization or two linear polarizers at 90 degrees.

Abstract: A telecommunications optical fiber is secured against intrusion by detecting manipulation of the optical fiber prior to an intrusion event. This can be used in a non-locating system where the detection end is opposite the transmit end or in a locating system which uses Fresnel reflections and Rayleigh backscattering to the transmit end to detect and then locate the motion. The Rayleigh backscattering time sliced data can be stored in a register until an intrusion event is detected. The detection is carried out by a polarization detection system which includes an optical splitter which is manufactured in simplified form for economic construction. This uses a non-calibrated splitter and less than all four of the Stokes parameters. It can use a polarimeter type function limited to linear and circular polarization or two linear polarizers at 90 degrees.

Abstract: A telecommunications optical fiber is secured against intrusion by detecting manipulation of the optical fiber prior to an intrusion event. This can be used in a non-locating system where the detection end is opposite the transmit end or in a locating system which uses Fresnel reflections and Rayleigh backscattering to the transmit end to detect and then locate the motion. The Rayleigh backscattering time sliced data can be stored in a register until an intrusion event is detected. The detection is carried out by a polarization detection system which includes an optical splitter which is manufactured in simplified form for economic construction. This uses a non-calibrated splitter and less than all four of the Stokes parameters. It can use a polarimeter type function limited to linear and circular polarization or two linear polarizers at 90 degrees.