A fiber optic based intrusion sensing system includes two or more fiber optic cables buried in a shallow trench in the ground, side by side in a predetermined nonzero distance to each other and at one or more predetermined depths. A dynamic distributed fiber optic interrogator measures a predetermined property related to a change in the length of the cables connected to it. A control unit is connected to all interrogators and analyzes the measurements of the predetermined property and identifies objects on the surface by combining the simultaneous measurements of all cables and correlating the measurements to the type of object on the ground surface, the location of the object on the perimeter, the weight, speed and direction of the object, particularly the direction in or out of the secured perimeter.

An optical fiber is monitored for an intrusion event where reflected optical signals are divided into streams each associated with a respective location on the optical fiber. Blocks of the streams are selected each containing a plurality of streams and the streams are collated, for example by averaging, to create a single stream to which an algorithm is applied to create coefficients which are compared with a threshold value to generate an output indicative of disturbance of the fiber by an intrusion event. Each block representative of a length of the fiber is thus treated as a zone and the detection algorithm is applied to each. This creates a DAS system that does not require unique tuning as each zone is independently monitored. Applying the above zone principles and algorithms to the DAS system also provides a high level of nuisance alarm and false alarm rejection.

A monitoring system according to the present disclosure includes a cable (20) comprising an optical fiber, a reception unit (31) configured to receive an optical signal including a pattern corresponding to a state of a monitoring target (10) from at least one optical fiber included in the cable (20) and to detect the pattern from the received optical signal, and a control unit (32) configured to detect the state of the monitoring target (10) based on the pattern.

There is disclosed herein a barrier assembly (1) adapted to inhibit access to an area. The assembly including at least two markers (2) operatively associated with each other to define an area where access is to be inhibited. Means to connect said markers and monitoring means adapted in use to determine if access to said area has been breached.

An asset such as a data transmission system, a perimeter security system, an oil well or a pipe line is monitored for events which are potentially damaging or threatening to the asset by installing an optical fiber continuously through the asset. The asset has many different zones of different physical condition, environment and/or of different risk factors which are expected therefore to generate different responses to events. The fiber is monitored using a distributed acoustic sensing (DAS) interrogator by effecting an analysis to determine the presence of an event in one or more of the zones The analysis includes applying different gauge length parameters to received data signals from the different zones at the same time.

A building comprising a plurality of rooms (10) includes a room occupancy sensing apparatus. A light source (20) emits a series of light pulses (22), a plurality of waveguides deliver light from the light source to output nodes (60) located in the rooms, and a signal capture unit (30) receives output signals resulting from light reflected by objects in the rooms. The apparatus detects movement, of for example a person (40), in a room and ascertains the room concerned by virtue of (i) detecting a difference between the shape of the waveform of the signal (24 i) received at the signal capture unit (30) in response to a first emitted light pulse and the shape of the waveform of the signal (24m) received at the signal capture unit in response to a second emitted light pulse and (ii) relating said reflected light pulses to the appropriate output node and therefore to the room (10) associated with that output node (60).

This application relates to apparatus and methods for monitoring of a perimeter having a barrier (101) such as a chain-link fence. The system (100) has a sensing optical fibre (102) suitable for fibre optic distributed acoustic sensing (DAS) deployed along at least part of said perimeter, with at least part of the sensing optical fibre being buried, e.g. in the ground (104) in the vicinity of the barrier. In addition the sensing fibre is mechanically coupled to at least one vibration transmitting element (106) which is mechanically coupled to the barrier. In use the sensing fibre is interrogated by a DAS sensor unit (103). Being buried the sensing fibre is hidden from view, protected from sabotage and has good acoustic coupling to the ground, e.g. for detecting disturbances of the ground. The vibration transmitting elements ensure that any disturbance of the barrier, e.g. fence, itself is also well coupled to the sensing fibre and can be detected.

A method is provided for monitoring optical cable for disturbance events by providing dual monitoring systems where optical signals are received from at least one optical fiber of the cable which are modified by disturbance events. Two separate and distinct algorithms are applied to the received optical signals to generate first and second outputs related to the disturbance event where in a control system information from the first and second outputs is used to determine if an alarm should be issued. The monitoring systems can use a single DAS system and operate on the same data independently preferably using one algorithm which uses ZONE processes to obtain data about different zones in the fiber. Alternatively two DAS systems can be used, one DAS system and one ZONE system or two ZONE systems. In all cases weather data can be used to assist the two algorithms in determining the presence of false alarms.

An asset such as a data transmission system, a perimeter security system, an oil well or a pipe line is monitored for events which are potentially damaging or threatening to the asset by installing an optical fiber continuously through the asset. The asset has many different zones of different physical condition, environment and/or of different risk factors which are expected therefore to generate different responses to events. The fiber is monitored using a distributed acoustic sensing (DAS) interrogator by effecting an analysis to determine the presence of an event in one or more of the zones The analysis includes applying different gauge length parameters to received data signals from the different zones at the same time.