The present invention provides novel apparatus and methods for fast quantitative measurement of perturbation of optical fields transmitted, reflected and/or scattered along a length of an optical fibre. The present invention can be used for point sensors as well as distributed sensors or the combination of both. In particular this technique can be applied to distributed sensors while extending dramatically the speed and sensitivity to allow the detection of acoustic perturbations anywhere along a length of an optical fibre while achieving fine spatial resolution. The present invention offers unique advantages in a broad range of acoustic sensing and imaging applications. Typical uses are for monitoring oil and gas wells such as for distributed flow metering and/or imaging, seismic imaging, monitoring long cables and pipelines, imaging within large vessel as well as for security applications.

The present invention provides novel apparatus and methods for fast quantitative measurement of perturbation of optical fields transmitted, reflected and/or scattered along a length of an optical fiber. The present invention can be used for point sensors as well as distributed sensors or the combination of both. In particular this technique can be applied to distributed sensors while extending dramatically the speed and sensitivity to allow the detection of acoustic perturbations anywhere along a length of an optical fiber while achieving fine spatial resolution. The present invention offers unique advantages in a broad range of acoustic sensing and imaging applications. Typical uses are for monitoring oil and gas wells such as for distributed flow metering and/or imaging, seismic imaging, monitoring long cables and pipelines, imaging within large vessel as well as for security applications.

An interferometer apparatus for an optical fiber system and method of use is described. The interferometer comprises an optical coupler and optical fibers which define first and second optical paths. Light propagating in the first and second optical paths is reflected back to the optical coupler to generate an interference signal. First, second and third interference signal components are directed towards respective first, second and third photodetectors. The third photodetector is connected to the coupler via a non-reciprocal optical device and is configured to measure the intensity of the third interference signal component directed back towards the input fiber. Methods of use in applications to monitoring acoustic perturbations and a calibration method are described.

An accurate measurement method and apparatus using an optical fiber are disclosed. A total change in optical length in an optical core in the optical fiber is determined that reflects an accumulation of all of the changes in optical length for multiple segment lengths of the optical core up to a point on the optical fiber. The total change in optical length in the optical core is provided for calculation of an average strain over a length of the optical core based on the detected total change in optical length.

A low-cost, data-fitting-free robust methodology configured to distinguish the coupling condition of an arbitrary resonance, applicable in one example to a micro-resonator of a multi-micro-resonator optical integrated circuit. The method includes registering the resonator cavity response to a rapid-phase shift of the on-resonance pump field. From the registered feature of the time-dependent transmission characteristic acquired with an optical detector, the sign of a difference between the values of intrinsic loss of the cavity and the coupling rate (.sub.i.sub.c) is directly read out, thereby resulting not only in a more accurate estimation of the intrinsic loss as compared with related art, but also in facilitating practically-realizable inspection of massively integrated photonic platforms with micro-resonators.

An apparatus includes an element to transmit a partial amount of first light guided through the M cores of a target object and second light guided through M optical waveguides, and to reflect remaining amount thereof, a first modulator to individually modulate the first light, a first detector to output a first signal based on the first light reflected by the element and the second light passing through the element, a second detector to output a second signal based on the first light passing through the element and the second light reflected by the element, an optical system configured such that the first light and the second light overlap in pairs on the first and second detectors, and a processing unit configured to output information about mode-dependent loss of the target object based on the first signal, the second signal, and information about modulation given by the first modulator.

Aspects of the present disclosure describe systems, methods. and structures in which guided acoustic Brillouin (GAWBS) noise is measured using a homodyne measurement technique and demonstrated using a number of optical fibers, such fibers being commonly used in contemporary optical communications systems. The measurements are made with single spans and determined to be consistent with separate multi-span long-distance measurements. Additionally, a technique for preparing an optical fiber exhibiting superior GAWBS noise characteristics by reducing coherence length of the optical fiber by spinning the fiber at a high rate during the drawing process such that birefringence coherence length is reduced.

There is provided a measurement apparatus including: an interference waveform generating unit that generates an interference waveform signal corresponding to interference light of first light with second light received by an imaging surface; a distribution measurement unit that measures a first optical electric-field distribution of an intensity and a phase of the first light at the imaging surface, based on the interference waveform signal; a distribution simulation unit that simulates second optical electric-field distributions of the intensity and the phase of the first light at a plurality of planes having different distances from the imaging surface in a direction opposite to a propagation direction of the first light propagated from an end surface of an optical waveguide, based on the measured first optical electric-field distribution; a selection unit that selects, from the plurality of planes, a plane at which an area of a region of the simulated second optical electric-field distributions is minimized; and an output unit that outputs information of the simulated second optical electric-field distributions at the selected plane to a predetermined device.

The present disclosure relates to a device, including: a first light source for outputting incident light to a measured optical fiber or optical device; a second light source for outputting local light for being multiplexed with transmitted light through the measured optical fiber or optical device; and a signal processing unit for performing digital signal processing on a light-receiving signal I(t) obtained by multiplexing the transmitted light and the local light, wherein the signal processing unit is configured to calculate an autocorrelation function between the light-receiving signal I(t) and a signal I(t+) obtained by shifting the light-receiving signal by a time , and to measure a delay time difference between propagation modes in the measured optical fiber or optical device, from a peak position of the autocorrelation function.

The present disclosure includes a light injecting unit that injects a frequency-swept probe light into one end of an optical fiber targeted for measurement, injects a pump light into the other end of the optical fiber targeted for measurement, with respect to the probe light, and thereby amplifies the probe light in the optical fiber targeted for measurement, a light receiving unit that receives a multiplexed light obtained by multiplexing a local light with the probe light, an interference waveform measurement unit that measures an interference waveform between the probe light and the local light, a fundamental mode time waveform analysis unit that acquires a fundamental mode time waveform of the probe light, based on the interference waveform, and a control calculation unit that calculates losses and crosstalk at loss and crosstalk occurrence points of the optical fiber targeted for measurement, based on the fundamental mode time waveform.