A system and method of delivering fiber optic communication service is provided. The method includes monitoring a strain signal generated by a strain-sensing optical fiber embedded in a roadway. The method includes comparing the strain signal to a predetermined allowable strain threshold of an optical communication cable associated with the strain-sensing optical fiber. The method includes relieving strain at a position along a length of the optical communications cable when the strain signal is determined to exceed the predetermined allowable strain threshold.

An optical probe that measures the level of a liquid in a tank includes a transparent and refracting optical waveguide for receiving an injection of a collimated light beam. The optical waveguide internally reflects the collimated light beam according to a total reflection regime in any part of the optical waveguide located in a gaseous medium and refracts the collimated light beam according to a refraction regime in any part of the optical waveguide immersed in a liquid medium. The optical waveguide switches from the total reflection regime to the refraction regime at the interface between the gaseous medium and the liquid medium, and mirrors are arranged around said optical waveguide and reverse the path of a light beam collimated and refracted by the optical waveguide, the optical path covered by the collimated light beam representing the level of the liquid in the tank.

The present invention provides a method for measuring an optical sensor system comprising an array of intrinsic fiber optic sensors at an interrogator comprising an optical source and an optical detector. The method comprises the steps of emitting an optical signal to an array of intrinsic fiber optic sensors; detecting optical responses to the emitted signal from the sensors; associating each detected optical response with an individual sensor by determining within which region among a plurality of detection regions assigned to the individual sensors the optical response is detected wherein each detection region corresponds to a wavelength range in the bandwidth of the optical sensor system; and performing signal processing on each optical response to measure the value of the physical parameter detected by its associated sensor. A calibration of the detection region assigned to each sensor is performed at predetermined intervals.

An optical cable structure is discussed that enables a distributed optical fiber sensor to detect acoustic vibration and other measurands, which could be, for example, changes in temperature, changes in static pressure, and changes in static strain. The optical cable structure includes first and second optical fibers disposed within a thin walled, elliptical, gel filled, loose tube helically wound within a cable wall of the optical cable structure. The optical cable structure further includes an additional optical fiber bonded to a strength member using a tight encapsulant. Because the additional optical fiber is fixed to the strength member and disposed with its axis parallel to the strength member, the additional optical fiber experiences the full axial strain on the optical cable structure, unlike the first and second optical fibers contained within the helically wound loose tube, thereby providing a contrast to the strain response coefficients of the first and second optical fibers.

A novel methodology for characterizing and calibrating an entangled photon distribution system is disclosed. The entangled photon distribution system includes at least a source of entangled photon pairs, two photon detectors which detect photons among two channels and a controller. The methodology includes: for at least two different operational setting levels of the source of entangled photon pairs, measuring count rates for photons detected by the two photon detectors, individually and coincidently; fitting the measured individual and coincidence count rate data for the at least two different operational setting levels with theoretical models of detection probability; and determining operational parameters of the system from the fitting. The determined operational parameters of the system include the rate of generated entangled photon pairs by the source, the rates of Raman-scattered photons generated in the first and second channels, respectively, and the efficiency of the two photon detectors, respectively.

An improved optical fiber distributed acoustic sensor system uses an optical fiber having reflector portions distributed along its length in at least a first portion. The reflector portions are positioned along the fiber separated by a distance that is equivalent to twice the distance an optical pulse travels along the fiber in a single sampling period of the data acquisition opto-electronics within the sensor system. No oversampling of the reflections of the optical pulses from the reflector portions is undertaken. The sampling points for data acquisition in the sensor system are aligned with the reflections that arrive at the sensor system from along the sensing fiber. Adaptive delay componentry adaptively aligns the reflected optical signals (or their electrical analogues) with the sampling points. Control over the sampling points can re-synchronise the sampling points with the returning reflections. Reflection equalisation componentry may reduce the dynamic range of the returning reflections.

Embodiments of the present invention provide a cable for optical fiber sensing applications formed from fiber wound around a cable core. A protective layer is then preferably placed over the top of the wound fiber, to protect the fiber, and to help keep it in place on the cable core. The cable core is preferably of a diameter to allow bend-insensitive fiber to be wound thereon with low bending losses. The effect of winding the fiber onto the cable core means that the longitudinal sensing resolution of the resulting cable is higher than simple straight fiber, when the cable is used with an optical fiber sensing system such as a DAS or DTS system. The achieved resolution for the resulting cable is a function of the fiber winding diameter and pitch, with a larger diameter and reduced winding pitch giving a higher longitudinal sensing resolution.

An active fiber stretcher assembly can be used for data acquisition systems. A time-break signal can be detected that coincides with a seismic event emitted from a seismic controller. A predetermined waveform can be generated in response to detecting the time-break signal. The predetermined waveform may be encoded onto a fiber optic cable using a fiber stretcher. A data acquisition system connected to the fiber optic cable may detect the predetermined waveform on the fiber optic cable and initiate acquisition operations including: receiving, during the seismic event, light signals returning from a portion of the fiber optic cable in a subterranean environment; determining one or more characteristics of the subterranean environment from the light signals; and storing the one or more characteristics.

A system (20) for fiber-optic reflectometry includes an optical source (28, 40), a beat detection module (44, 48, 52, 56A, 56B) and a processor (36). The optical source is configured to generate a non-linearly-scanning optical interrogation signal having an instantaneous optical frequency that is a non-linear function of time. The beat detection module is configured to transmit the optical interrogation signal into an optical fiber (24), to receive from the optical fiber an optical backscattering signal in response to the optical interrogation signal, and to mix the optical backscattering signal with a reference replica of the optical interrogation signal, so as to produce a beat signal. The processor is configured (i) to hold a predefined function that is indicative of an expected phase of the beat signal resulting from the non-linearly-scanning optical interrogation signal as a function of position along the optical fiber and time, (ii) to estimate a backscattering profile of the optical fiber by applying the predefined function to the beat signal, and (iii) to sense one or more events affecting the optical fiber by analyzing the backscattering profile.

A steel cable includes steel wires and at least one light wave guide which is surrounded by the steel wires and provided for detecting load-dependent cable strains, and has a glass fiber surrounded by a plastic casing. At least the steel wires closest to the light wave guide are crimped with the light wave guide and permanently pressed against the casing surface thereof, whereby the cross-sectional shape of the casing surface of the light wave guide deviates from an unloaded shape, in particular a circular shape, and the light wave guide is clamped continuously along at least one part of the longitudinal extension thereof, in a slip-free manner between the steel wires closest to same. A method produces a steel cable of this type.