A sensor fiber for the detection of changes of temperature, bending, and/or torsion includes a multicore optical waveguide with a fiber Bragg grating (FBG) structure. One embodiment contains at least two FBG cores and a surrounding cladding. The sensor fiber is characterized by one or more distinction and orientation means which produce a marker zone to assign and label each individual FBG core.

A distributed Brillouin sensor system comprising a pump laser, and a combined fiber assembly including at least a first optical fiber section and a second optical fiber section is described. The pump laser is arranged so as to send a pump signal into a first end of combined fiber assembly, and the detector system is arranged to detect Brillouin backscattering from the combined fiber assembly. The combined fiber assembly is characterized by the first section having a low Brillouin gain, and the second fiber section having a high Brillouin gain.

The single-mode optical fibers have a core region that includes an inner core region having a delta value .sub.1 and a radius r.sub.1 immediately surrounded by an outer core region of radius r.sub.2 and a delta value .sub.2<.sub.1, wherein .sub.1-.sub.2 is in the range from 0.3% to 2%. A cladding region of radius r.sub.3 immediately surrounds the core region. The inner and outer regions define an annular width r=r.sub.2r.sub.1. At least one of r.sub.1, r.sub.2, r and r.sub.3 changes with a period p in the longitudinal direction between first and second values each having a corresponding level distance d.sub.F. The change occurs over a transition distance d.sub.T such that d.sub.T/d.sub.F<0.1. The Brillouin frequency shift f changes by an amount [f] that is least 10 MHz over each period p, thereby allowing for Brillouin frequency-shift management in fiber-based sensor systems.

Systems, methods, and devices of the various embodiments enable mitigation of the effects of birefringence in Optical Frequency Domain Reflectometer (OFDR) sensing fiber. Various embodiments enable the measurement of the polarization state of the light in a sensing fiber throughout the entire sensing cable in a highly distributed manner typical of OFDR systems. Various embodiments enable the production of a distributed fiber birefringence measurement throughout the length of an OFDR sensing fiber. Various embodiments may enable OFDR to be 100% polarization diverse, meaning that polarization effects in the fiber optic cables and sensing fiber do not negatively effect measurements. Additionally, the highly distributed measurement of the polarization state and related birefringence in a sensing fiber of the various embodiments may enable new types of measurements such as pressure, twisting, and bending along the sensing fiber.

A distributed Brillouin sensor system comprising a pump laser, a Brillouin sensor fiber, and a detector system is described. The pump laser is arranged so as to send a pump signal into a first end of the Brillouin sensor fiber, and the detector system is arranged to detect Brillouin backscattering from the Brillouin sensor fiber. The Brillouin sensor fiber is characterized by having a negative dispersion, and further by an effective area of the sensor fiber being less than or equal to 50 m.sup.2.

The present invention discloses an integrated system for optical fiber sensing and communication through sharing co-frequency resources. Specifically, the system consists of two parts: optical path detection and circuit demodulation. The entire system consists of a continuous wave laser, a fiber coupler, a polarization controller, a mach-zehnder modulator, an arbitrary waveform generator, an erbium-doped fiber amplifier, an optical filter, an optical fiber annular, an optical fiber, a photodetector, a data acquisition device, a balance detector and a data acquisition card. A transmission optical signal and a sensing detection light are generated by the same laser, transmission performance and sensing performance of the system are changed by adjusting modulation power of a transmission signal, the transmission signal is obtained by using direct detection at far-end, a sensing signal is obtained by using heterodyne coherent detection at local-end. The present invention provides a simple, compact and high-efficiency integrated system for co-frequency sharing optical fiber sneisng and communication, to solve the deficiencies of the existing integrated system in practical applications.

Fiber optic cables with improved performance for use in distributed sensing, for instance in distributed acoustic sensors, are disclosed. In one embodiment a fiber optic cable (210) comprises a core (208) and cladding (206) disposed within a buffer material (202) surrounded by a jacket (204) and arranged so that the core is offset from the center of the cable. By offsetting the core from the center of the jacket any bending effects on the core can be maximized compared to the core being located at the center of the cable.

Fiber optic sensors based on multicore optical fibers that are intended for use in harsh environment sensing. This multicore fiber comprises an arrangement of optically coupled cores in a silica background. Sensors are fabricated by splicing a section of multicore fiber between two single mode fibers. This multicore fiber sensor is simple and repeatable to fabricate and multiple sensors can be multiplexed in a chain. These fiber optic sensors are intended for a broad set of sensing applications including temperature, pressure, strain, bending, acoustic vibrations, mechanical vibrations, or combinations thereof.

Fiber optic sensors based on multicore optical fibers that are intended for use in harsh environment sensing. This multicore fiber comprises an arrangement of optically coupled cores in a silica background. Sensors are fabricated by splicing a section of multicore fiber between two single mode fibers. This multicore fiber sensor is simple and repeatable to fabricate and multiple sensors can be multiplexed in a chain. These fiber optic sensors are intended for a broad set of sensing applications including temperature, pressure, strain, bending, acoustic vibrations, mechanical vibrations, or combinations thereof.

Fiber optic cables with improved performance for use in distributed sensing, for instance in distributed acoustic sensors, are disclosed. In one embodiment a fiber optic cable (210) comprises a core (208) and cladding (206) disposed within a buffer material (202) and surrounded by a jacket (204) and arranged so that the core is offset from the center of the cable. By offsetting the core from the center of the jacket any bending effects on the core can be maximised compared with the core being located at the center of the cable.