Abstract: A method is provided for detecting intrusion into optical fibers of a Passive Optical Network (PON) of the type which includes a multiplexing system at the head end for separating a data signal output at the head end to the plurality of fibers for supply to user end terminals and a data transmission system at each of the user end terminals for entering onto the fiber data as an optical signal. The method includes providing a monitor system having a transmitter at the head end and a monitor signal analysis system for analyzing changes in the optical monitor signal after transmission along the fiber for detecting an intrusion event. A monitor signal analysis system is provided at one or more user end terminals for detection and conversion of data from the analysis into a digital signal which is then transmitted from the user end terminals back to the head end using the data transmission system through the PON system or separately from the PON system.

Abstract: A method is provided for detecting intrusion into optical fibers of a Passive Optical Network (PON) of the type which includes a multiplexing system at the head end for separating a data signal output at the head end to the plurality of fibers for supply to user end terminals and a data transmission system at each of the user end terminals for entering onto the fiber data as an optical signal. The method includes providing a monitor system having a transmitter at the head end and a monitor signal analysis system for analyzing changes in the optical monitor signal after transmission along the fiber for detecting an intrusion event. A monitor signal analysis system is provided at one or more user end terminals for detection and conversion of data from the analysis into a digital signal which is then transmitted from the user end terminals back to the head end using the data transmission system through the PON system or separately from the PON system.

Abstract: A method is provided for detecting movement indicative of intrusion events on optical drop fibers of a network where the individual drop fiber can be identified to locate the event. The method uses a monitor system at the network end and multiplexing the monitor signal along the individual fibers to the respective terminals. At each of the terminals, the monitor signal is returned unchanged or in modified form along the same or different fibers to the network end. At the network end the received monitor signals is analyzed for changes in said monitor signals indicative of movement. Which one or more of the drop fibers has triggered the alarm is determined by modifying the monitor signal in wavelength or polarization, or by applying a modulation at the source and/or at multiplexing and/or at returning so that the monitor signal of one drop fiber has a difference from the monitor signal of another drop fiber.

Abstract: A method is provided for detecting movement indicative of intrusion events on optical drop fibers of a network where the individual drop fiber can be identified to locate the event. The method uses a monitor system at the network end and multiplexing the monitor signal along the individual fibers to the respective terminals. At each of the terminals, the monitor signal is returned unchanged or in modified form along the same or different fibers to the network end. At the network end the received monitor signals is analyzed for changes in said monitor signals indicative of movement. Which one or more of the drop fibers has triggered the alarm is determined by modifying the monitor signal in wavelength or polarization, or by applying a modulation at the source and/or at multiplexing and/or at returning so that the monitor signal of one drop fiber has a difference from the monitor signal of another drop 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.