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 purpose of the present invention is to provide a device for optical frequency domain reflectometry and a method thereof that can measure a reflectance distribution with less spatial resolution degradation due to a phase noise, without using a wideband receiving system even when a long-distance measurement is performed. The device for optical frequency domain reflectometry according to the present invention is provided with a delay optical fiber for delaying a local light by a prescribed time, and obtains information on a relative delay of a backscattered light from an optical fiber under measurement with respect to the local light and information on the positivity and the negativity of a beat frequency by measuring an in-phase component and a quadrature component of a beat signal obtained by multiplexing the backscattered light from the optical fiber under measurement and the local light delayed by the delay optical fiber, so as to obtain a reflectance distribution in a longitudinal direction of the optical fiber under measurement based on these pieces of information.

Multi-spectral feature sensing techniques and sensor and related digital signal processing circuitry and methods. A method of operating a digital signal processing circuitry includes acquiring optical frequency domain reflectometry (OFDR) data from an interferometer operably coupled to a tunable laser and a sensing fiber, separating sensor signals corresponding to sensors of the sensing fiber from the OFDR data, and inferring a relative shift of a separated sensor signal. A digital signal processing circuitry includes a front end circuitry and a back end circuitry. The front end circuitry is configured to isolate sensor responses from an input signal including OFDR data. The back end circuitry is configured to determine a phase shift corresponding to each isolated sensor response.

It is an object of the present invention to provide an aerial optical fiber cable inspection method, an aerial optical fiber cable inspection device, and a program which can identify a cable sagging section from vibration sensing results. In the aerial optical fiber cable inspection method according to the present invention, a vibration distribution waveform along the longitudinal direction of an aerial optical fiber cable measured using an optical fiber vibration sensing device is received as an input, a standard deviation of the amplitude of vibration at each position in the vibration distribution waveform is calculated, and a section with a standard deviation larger than that of other sections is identified as a cable sagging section.

The present invention relates to a method and device for measuring optical nonlinearity of an optical fiber to be measured comprising a plurality of cores having mutually coupled waveguide modes. The method includes, at least, preparing a laser light source emitting laser light and a detecting unit determining an optical intensity, inputting laser light into a specific core of the optical fiber to be measured, determining the intensity of a specific wavelength component caused by optical nonlinearity among the reflective light components from the optical fiber to be measured, and determining optical nonlinearity of the optical fiber to be measured on the basis of the intensity of the specific wavelength component.

A system and method for performing an in-service optical time domain reflectometry test, an in-service insertion loss test, and an in-service optical frequency domain reflectometry test using a same wavelength as the network communications for point-to-point or point-to-multipoint optical fiber networks while maintaining continuity of network communications are disclosed.

Various embodiments of sensors are described that exhibit several spectral features that together offer coverage of a wavelength range corresponding to the desired strain dynamic range (or temperature range) of a system. The spectral features arise from a Fabry-Perot interferometer formed by two overlapping chirped FBGs, the free-spectral range (FSR) of which varies with wavelength. The spectral features may be differentiated due to a combination of spacing and slope of the overlapped, chirped gratings.

An improved technique for acoustic sensing involves, in one embodiment, launching into a medium, a plurality of groups of pulse-modulated electromagnetic-waves. The frequency of electromagnetic waves in a pulse within a group differs from the frequency of the electromagnetic waves in another pulse within the group. The energy scattered by the medium is detected and, in one embodiment, the beat signal may be used to determine a characteristic of the environment of the medium. For example, if the medium is a buried optical fiber into which light pulses have been launched in accordance with the invention, the presence of acoustic waves within the region of the buried fiber can be detected.

According to examples, a fiber-optic testing source for testing a multi-fiber cable may include a laser source communicatively coupled to a plurality of optical fibers connected to a connector. The fiber-optic testing source may include at least one photodiode communicatively coupled to at least one of the plurality of optical fibers by at least one corresponding splitter to implement a communication channel between the fiber-optic testing source and a fiber-optic testing receiver. The communication channel may be operable independently from a polarity associated with the multi-fiber cable. The fiber-optic testing receiver may include a plurality of photodiodes communicatively coupled to a plurality of optical fibers. The fiber-optic testing receiver may include at least one laser source communicatively coupled to at least one of the plurality of optical fibers by at least one corresponding splitter to implement the communication channel between the fiber-optic testing receiver and a fiber-optic testing source.

Multi-spectral feature sensing techniques and sensor and related digital signal processing circuitry and methods. A method of operating a digital signal processing circuitry includes acquiring optical frequency domain reflectometry (OFDR) data from an interferometer operably coupled to a tunable laser and a sensing fiber, separating sensor signals corresponding to sensors of the sensing fiber from the OFDR data, and inferring a relative shift of a separated sensor signal. A digital signal processing circuitry includes a front end circuitry and a back end circuitry. The front end circuitry is configured to isolate sensor responses from an input signal including OFDR data. The back end circuitry is configured to determine a phase shift corresponding to each isolated sensor response.