A system for interrogating sensors in a fiber optical sensor network includes groups of sensors. The sensors in one group operate at different wavelengths, and the sensors of other groups may have overlapping wavelengths. A light source generates a broadband light signal, input and output means for guides the broadband light to the fiber optical sensor network for illuminating the sensors and for coupling the light signal coming from the sensors of the fiber optical sensor network to the detection system, and a detection system detects the received light signal, during a detection integration time. The system is arranged for selecting pre-dominantly the received light coming from the different sensors of a selected group of sensors using a code-division multiplexing technique and simultaneously detecting sensors of the selected group of sensors using a wavelength-division multiplexing technique.

A system for detecting an intrusion of at least one of a monitoring fiber and a detector comprises a sensor having a closure monitor and an intrusion monitor, the closure monitor including a signal generator and at least one detector attached to the monitoring fiber. The signal generator transmits signal light such that the monitoring fiber receives the transmitted signal light and reflects a portion of the signal light via the at least one detector to the closure monitor and transmits a non-reflected portion of the signal light. The intrusion monitor receives the transmitted non-reflected portion of the signal light, and monitors the non-reflected portion of the signal light to detect transient changes in the non-reflected portion of the signal light indicative of at least one of a vibration, a motion and a handling of at least one of the monitoring fiber and the at least one detector.

A system for interrogating sensors in a fiber optical sensor network includes groups of sensors. The sensors in one group operate at different wavelengths, and the sensors of other groups may have overlapping wavelengths. A light source generates a broadband light signal, input and output means for guides the broadband light to the fiber optical sensor network for illuminating the sensors and for coupling the light signal coming from the sensors of the fiber optical sensor network to the detection system, and a detection system detects the received light signal, during a detection integration time. The system is arranged for selecting pre-dominantly the received light coming from the different sensors of a selected group of sensors using a code-division multiplexing technique and simultaneously detecting sensors of the selected group of sensors wavelength-division multiplexing technique.

A system for detecting an intrusion of at least one of a monitoring fiber and a detector comprises a sensor having a closure monitor and an intrusion monitor, the closure monitor including a signal generator and at least one detector attached to the monitoring fiber. The signal generator transmits signal light such that the monitoring fiber receives the transmitted signal light and reflects a portion of the signal light via the at least one detector to the closure monitor and transmits a non-reflected portion of the signal light. The intrusion monitor receives the transmitted non-reflected portion of the signal light, and monitors the non-reflected portion of the signal light to detect transient changes in the non-reflected portion of the signal light indicative of at least one of a vibration, a motion and a handling of at least one of the monitoring fiber and the at least one detector.

A system for detecting an intrusion of at least one of a monitoring fiber and a detector comprises a sensor having a closure monitor and an intrusion monitor, the closure monitor including a signal generator and at least one detector attached to the monitoring fiber. The signal generator transmits signal light such that the monitoring fiber receives the transmitted signal light and reflects a portion of the signal light via the at least one detector to the closure monitor and transmits a non-reflected portion of the signal light. The intrusion monitor receives the transmitted non-reflected portion of the signal light, and monitors the non-reflected portion of the signal light to detect transient changes in the non-reflected portion of the signal light indicative of at least one of a vibration, a motion and a handling of at least one of the monitoring fiber and the at least one detector.

There is disclosed a distributed optical fibre sensing system in which the sensor fibre comprises at least first and second waveguides used for separate sensing operations. The sensor fibre may be, for example, a double clad fibre having a monomode core and a multimode inner cladding.

A system for detecting an intrusion of at least one of a monitoring fiber and a detector comprises a sensor having a closure monitor and an intrusion monitor, the closure monitor including a signal generator and at least one detector attached to the monitoring fiber. The signal generator transmits signal light such that the monitoring fiber receives the transmitted signal light and reflects a portion of the signal light via the at least one detector to the closure monitor and transmits a non-reflected portion of the signal light. The intrusion monitor receives the transmitted non-reflected portion of the signal light, and monitors the non-reflected portion of the signal light to detect transient changes in the non-reflected portion of the signal light indicative of at least one of a vibration, a motion and a handling of at least one of the monitoring fiber and the at least one detector.

There is disclosed a distributed optical fibre sensing system in which the sensor fibre comprises at least first and second waveguides used for separate sensing operations. The sensor fibre may be, for example, a double clad fibre having a monomode core and a multimode inner cladding.

The disclosure relates to a distributed optical fibre sensor having an optical switch arranged to selectively and simultaneously couple each of a plurality of interrogators to each of a plurality of sensing optical fibres.

The optical fiber sensing system includes: a host sensing device including a first optical sensor for receiving, from a first optical fiber, first light corresponding to first pulse light input into the first optical fiber and first signal light and outputting first data for the first optical fiber corresponding to the first light and second data included in the first signal light, and a first data communicator for outputting a data signal including the first data and second data; and a remote sensing device including a second optical sensor for receiving, from a second optical fiber, second light that corresponds to second pulse light input into the second optical fiber and outputting second data including sensing results for the second optical fiber corresponding to the second light, and a second data communicator for outputting, to the first optical fiber, first signal light including the second data.