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.

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.

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.

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 temperature or strain distribution sensor may include a photodiode to acquire a beat frequency between a first laser beam and a second laser beam. A modulator may modulate the first laser beam that is to be injected into a device under test (DUT). A coherent receiver may acquire a backscattered signal from the DUT, and use the second laser beam as a local oscillator to determine a Brillouin trace with respect to the DUT. The Brillouin trace may be used to determine a Brillouin frequency shift and a Brillouin power for the DUT to implement an absolute referencing of a Rayleigh reference trace. The coherent receiver may determine, relative to the Rayleigh reference trace, a further Brillouin frequency shift and a Rayleigh frequency shift to determine a temperature or a strain associated with the DUT.

The ends of sensing and interrogating multicore fibers are brought into proximity for connection in a first orientation with one or more cores in the sensing fiber being paired up with corresponding one or more cores in the interrogating fiber. Optical interferometry is used to interrogate at least one core pair and to determine a first reflection value that represents a degree of alignment for the core pair in the first orientation. The relative position is adjusted between the ends of the fibers to a second orientation. Interferometry is used to interrogate the core pair and determine a second reflection value that represents a degree of alignment for the core pair in the second orientation. The first reflection value is compared with the second reflection value, and an aligned orientation is identified for connecting the sensing and interrogating fibers based on the comparison.

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.

To sense the shape of a multicore optical fiber sensor, light reflected in a center and two or more helixed outer cores of the optical fiber sensor is measured, and phases associated with strain in the center and helixed outer cores is tracked along the length of the fiber sensor. Further, a wobble signal indicative of a variation in the spin rate of the fiber sensor is determined. Based on the tracked phases and the wobble signal, the fiber shape is computed.