Abstract: According to the invention, these aims are achieved by means of a sensor, suitable for sensing one or more properties of one or more structures, the sensor comprising, a first optical propagation path which is configurable to cooperate with a structure whose properties are to be sensed; a second optical propagation path which is configurable to cooperate with a structure whose properties are to be sensed; a third optical propagation path; a means for amplifying a signal which propagates in the third optical propagation path, so that the signal is amplified before it begins propagation along the second optical propagation path, and a means to prevent the propagation of signals from the second optical propagation path to the third optical propagation path. There is further provided a corresponding method of sensing.

Abstract: The present invention relates to a method of sensing permanent deformation of a structure, the method comprising the steps of; determining the strain required to permanently deform a structure; securing to the structure one or more strain sensors so that a strain sensor will deform when the structure is deformed, wherein the or each strain sensor comprises one or more optical fibers and wherein the or each strain sensor is configured such that it will permanently deform only when the structure permanently deforms; carrying out distributed fiber optic analysis to sense if a strain sensor has been permanently deformed, wherein a permanent deformation of a strain sensor indicates permanent deformation of the structure. The present invention also relates to a corresponding assembly.

Abstract: According to the invention, these aims are achieved by means of a sensor, suitable for sensing one or more properties of one or more structures, the sensor comprising, a first optical propagation path which is configurable to cooperate with a structure whose properties are to be sensed; a second optical propagation path which is configurable to cooperate with a structure whose properties are to be sensed; a third optical propagation path; a means for amplifying a signal which propagates in the third optical propagation path, so that the signal is amplified before it begins propagation along the second optical propagation path, and a means to prevent the propagation of signals from the second optical propagation path to the third optical propagation path. There is further provided a corresponding method of sensing.

Abstract: The present invention relates to a method of sensing permanent deformation of a structure, the method comprising the steps of; determining the strain required to permanently deform a structure; securing to the structure one or more strain sensors so that a strain sensor will deform when the structure is deformed, wherein the or each strain sensor comprises one or more optical fibers and wherein the or each strain sensor is configured such that it will permanently deform only when the structure permanently deforms; carrying out distributed fiber optic analysis to sense if a strain sensor has been permanently deformed, wherein a permanent deformation of a strain sensor indicates permanent deformation of the structure. The present invention also relates to a corresponding assembly.

Abstract: A distributed Brillouin sensor system is provided. The system has two distributed feedback (DFB) lasers, which are locked at the Brillouin frequency of the optical fiber through offset locking method by coupler splitting into two parts. The split parts are sent to two photodiodes, the outputs of which are sent to a mixer. A PID controller means follows the mixer and a current controller follows the PID controller. The lasers have a wavelength of 1550 nm. The PID controller locks the frequency difference. An optical delay line is used to produce the frequency tuning of the two DFB lasers around the Brillouin frequency of the optical fibers. The lock-in amplifier is used to keep the DC level of the optical modulator at minimum.

Abstract: A distributed Brillouin sensor system is provided. The system has two distributed feedback (DFB) lasers, which are locked at the Brillouin frequency of the optical fiber through offset locking method by coupler splitting into two parts. The split parts are sent to two photodiodes, the outputs of which are sent to a mixer. A PID controller means follows the mixer and a current controller follows the PID controller. The lasers have a wavelength of 1550 nm. The PID controller locks the frequency difference. An optical delay line is used to produce the frequency tuning of the two DFB lasers around the Brillouin frequency of the optical fibers. The lock-in amplifier is used to keep the DC level of the optical modulator at minimum.