The disclosed technology includes, among others, methods and devices for measuring distributed fiber bend or stress related characteristics along an optical path of fiber under test (FUT) uses both a light input unit and a light output unit connected to the FUT at one single end.

An integrating sphere-equipped optical measurement device and optical connector polarity and type identification and loss measurement are provided. The optical measurement device includes at least two photodetectors that are optically responsive over different ranges of wavelengths. The optical measurement device receives one or more optical signals emanate from optical fibers of an optical fiber cable. The optical measurement device determines an optical intensity or loss of the one or more optical signals based on a measurement made by a corresponding photodetector whose responsivity range includes a wavelength of the one or more optical signals. The optical measurement device determines one or more respective positions where the one or more optical signals impinged on a sensor. The optical measurement device determines a polarity of the optical fiber cable based on both the one or more positions and one or more or transmitting positions of the one or more optical signals, respectively.

An optical line testing device for measuring at least a cutting position of an optical line according to the present invention includes: a first wavelength tunable laser source configured to generate a first optical signal in which a plurality of wavelengths appear alternately and periodically; a second wavelength tunable laser source configured to generate a second optical signal which is identical to the first optical signal but has an adjustable delay time; and an interferometer configured to cause interference between a reflected optical signal, corresponding to the first optical signal, which is returning after having been emitted to the optical line, and the second optical signal to output an interference signal.

An apparatus includes a light source that causes continuous oscillation light to enter one terminal of an optical transmission line, wherein the continuous oscillation light is to propagate a light variation of a first physical amount generated on the optical transmission line to another terminal of the optical transmission line; a photodetector that detects, on the one terminal, light turned back from a light modulation converter provided on the another terminal, wherein the light modulation converter obtains the turned-back light by converting the light variation of the first physical amount into a light variation of a second physical amount; and a processor that calculates a light-variation location generated on the optical transmission line by comparing time variations in the light variation of the first physical amount and the light variation of the second physical amount in the light detected by the photodetector.

A system (20) for fiber-optic reflectometry includes an optical source (28, 40), a beat detection module (52, 56) and a processor (36). The optical source is configured to generate an optical interrogation signal that is transmitted into an optical fiber (24). The beat detection module is configured 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 using In-phase/Quadrature (I/Q) mixing, so as to produce a complex beat signal having In-phase (I) and Quadrature (Q) components. The processor is configured to sense one or more events affecting the optical fiber by analyzing the I and Q components of the complex beat signal.

The optical fiber sensor includes a setting unit which sets a section to be evaluated set in the optical fiber to one of a first section and a plurality of second sections, each of which is shorter than the first section, an extraction unit which extracts a state change of light from the optical fiber, and a detection unit which detects a change in the surrounding environment based on time-series data of the state change of light in the section to be evaluated.

According to examples, a Brillouin and Rayleigh distributed sensor may include a first laser source to emit a first laser beam, and a second laser source to emit a second laser beam. A photodiode may acquire a beat frequency between the two laser beams. The beat frequency may be used to maintain a predetermined offset frequency shift between the two laser beams. A modulator may modulate the first laser beam. The modulated first laser beam is to be injected into a device under test (DUT), A coherent receiver may acquire a backscattered signal from the DUT. The backscattered signal results from the modulated first laser beam injected into the DUT. The coherent receiver may use the second laser beam as a local oscillator to determine Brillouin and Rayleigh traces with respect to the DUT based on the predetermined offset frequency shift.

The present disclosure provides a method and system of identifying macro-bends in at least one test fiber. The method includes generation of modulated optical pulses and scrambling the state of polarization of the modulated optical pulses to random states of polarization. The method includes injection of the modulated optical pulses in at least one test fiber and reception of backscattered optical pulses and splitting of the backscattered optical pulses to a first optical component and a second component. The method includes measurement of a first power of the first optical component and a second power of the second optical component of the backscattered optical pulses. The method includes calculation of discrete values of polarization dependent loss as a function of distance and identification of the macro-bends by analysis of peaks in one or more plots of one or more traces of the discrete values of the polarization dependent loss.

An optical fiber includes multiple optical waveguides configured in the fiber. An interferometric measurement system mitigates or compensates for the errors imposed by differences in a shape sensing optical fiber's response to temperature and strain. A 3-D shape and/or position are calculated from a set of distributed strain measurements acquired for a multi-core optical shape sensing fiber that compensates for these non-linear errors using one or more additional cores in the multicore fiber that react differently to temperature changes than the existing cores.

An apparatus includes a light source that causes continuous oscillation light to enter one terminal of an optical transmission line, wherein the continuous oscillation light is to propagate a light variation of a first physical amount generated on the optical transmission line to another terminal of the optical transmission line; a photodetector that detects, on the one terminal, light turned back from a light modulation converter provided on the another terminal, wherein the light modulation converter obtains the turned-back light by converting the light variation of the first physical amount into a light variation of a second physical amount; and a processor that calculates a light-variation location generated on the optical transmission line by comparing time variations in the light variation of the first physical amount and the light variation of the second physical amount in the light detected by the photodetector.