The present disclosure relates to a frequency modulation amount measuring device that measures an optical spectral shift of scattered light at a position in an optical transmission line, and calculates a frequency modulation amount at the position, using the measured optical spectral shift.

An object of the present disclosure is to provide an optical fiber cable monitoring method and an optical fiber cable monitoring system capable of linking information obtained from a measurement result with information stored in a DB and accurately specifying a loss occurrence location on an optical fiber cable. The optical fiber cable monitoring method according to the present disclosure uses two types of optical fiber measurement techniques having different sensitivities. Each of closure locations on the optical fiber cable is acquired with a high-sensitivity measurement technique, and geographical location information and the closure locations on the optical fiber are linked in an arrangement order of the closures. Thus, an operator can recognize an actual location (geographical location information) of a closure that is linked to a location of a point of abnormality on the optical fiber cable when an abnormality in the closure is detected with a low-sensitivity measurement technique.

An optical frequency-domain reflectometer (OFDR) capable of estimating the transfer matrix of a multimode optical fiber using mode-selective measurements performed from a single end of the fiber. In an example embodiment, the multimode optical fiber includes distributed reflectors designed to generate relatively strong light reflections along the length of the fiber at a desired spatial resolution. The embodiments may employ a signal-processing algorithm to estimate the fiber's transfer matrix by estimating segment transfer matrices corresponding to the fiber segments located between different ones of the distributed reflectors. Different embodiments of the disclosed OFDR can beneficially be adapted for use in different applications, such as fiber-optic component and module characterization, distributed optical sensing, biomedical imaging, OCT, etc.

A multi-core fiber includes multiple optical cores, and for each different core of a set of different cores of the multiple optical cores, a total change in optical length is detected. The total change in optical length represents an accumulation of all changes in optical length for multiple segments of that different core up to a point on the multi-core fiber. A difference is determined between the total changes in optical length for cores of the set of different cores. A twist parameter and/or a bend angle associated with the multi-core fiber at the point on the multi-core fiber is/are determined based on the difference.

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.

A device for determining a layer thickness in a multilayer film includes a radiation source configured to generate an electromagnetic primary radiation, a detector configured to detect an electromagnetic secondary radiation emitted by the multilayer film, the secondary radiation being induced by an interaction of the primary radiation with the multilayer film, and a first contact block transparent to the electromagnetic primary radiation and having a first contact surface for creating contact with the multilayer film. The radiation source is arranged on the first contact block in such a way that the electromagnetic primary radiation is guided from the first contact block onto the multilayer film.

A multi-core fiber includes multiple optical cores, and for each different core of a set of different cores of the multiple optical cores, a total change in optical length is detected. The total change in optical length represents an accumulation of all changes in optical length for multiple segments of that different core up to a point on the multi-core fiber. A difference is determined between the total changes in optical length for cores of the set of different cores. A twist parameter and/or a bend angle associated with the multi-core fiber at the point on the multi-core fiber is/are determined based on the difference.

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.

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.