24results about "Reflectometers dealing with polarization" patented technology

A testing method for an optical fiber is provided. The method involves the use of a P-OTDR device to launch polarized light pulses from the P-OTDR device into the fiber extremity of an optical fiber and obtain a return light signal. Concurrently, a polarization state of light travelling in a distal fiber segment is varied, a polarization component of the return light signal is isolated, and a set of P-OTDR traces are acquired. The set of P-OTDR traces is processed to detect a change in polarization of the return light signal. Upon detecting such a change an information relative to the distal fiber segment and the fiber extremity can be reported. The method may for example be used as a fiber identification method or a geo-referencing method. A P-OTDR device is also provided.

A system for monitoring the strength of optical back-scattering strength along an optical fiber line includes an optical transmitter, a coherent optical receiver, and a processor. The optical transmitter is configured to probe the line with light that is phase-modulated with repetitions of code sequences longer that the round-trip time in the fiber line. The coherent receiver uses homodyne detection to convert light retuned by the optical fiber line to obtain a time sequence of return signal measurements. The processor correlates successive segments of the return signal measurements with the modulation code to obtain a time sequence of intensity response estimates, and generates a back-scattering intensity profile for the optical fiber line by time-averaging corresponding portions of the intensity response estimates.

An optical measurement system in which a coherent light source generates a light signal, and a launch stage receives the light signal from the light source and generates a test signal. The test signal is launched along an optical path. The launch stage includes a first IQ modulator for controlling the test signal. The optical measurement system further includes a local oscillator stage configured to generate a local oscillator signal, wherein local oscillator stage has a second IQ modulator for controlling the local oscillator signal. A detector stage of the system is configured to receive the local oscillator signal from the local oscillator stage and a scattered signal from the optical path, and interfere the local oscillator signal with the scattered signal. The optical measurement system is implemented with one or more photonic integrated circuits.

The present invention relates to a method of re-connecting a first optical fiber (12) with a second optical fiber (34), the first fiber (12) and the second fiber (34) each having a plurality of outer cores, comprising: (a) positioning a first end section of the first fiber (12) and a second end section of the second fiber (34) in proximity so as to be aligned with one another along a longitudinal axis of the first and second end sections in a current connection position including a current connection orientation, in which a current relative rotational angle between the first and second end sections about the longitudinal axis is not known with respect to a relative rotational angle between the first and second end sections in a registered connection orientation determined with respect to a coordinate system during a previous connection of the first fiber (12) with the second fiber (34); (b) optically interrogating the outer cores of the first and second fibers (12, 34) through the current connection position to receive optical signals from the outer cores; (c) modifying, from the optical interrogation of the outer cores, the registered connection orientation such that the first and second fibers in the current connection orientation including the current relative rotational angle between the first and second end sections about the longitudinal axis are correctly registered with respect to the coordinate system.

The present invention relates to a method of re-connecting a first optical fiber (12) with a second optical fiber (34), the first fiber (12) and the second fiber (34) each having a plurality of outer cores, comprising: (a) positioning a first end section of the first fiber (12) and a second end section of the second fiber (34) in proximity so as to be aligned with one another along a longitudinal axis of the first and second end sections in a current connection position including a current connection orientation, in which a current relative rotational angle between the first and second end sections about the longitudinal axis is not known with respect to a relative rotational angle between the first and second end sections in a registered connection orientation determined with respect to a coordinate system during a previous connection of the first fiber (12) with the second fiber (34); (b) optically interrogating the outer cores of the first and second fibers (12, 34) through the current connection position to receive optical signals from the outer cores; (c) modifying, from the optical interrogation of the outer cores, the registered connection orientation such that the first and second fibers in the current connection orientation including the current relative rotational angle between the first and second end sections about the longitudinal axis are correctly registered with respect to the coordinate system.

There is provided a method of measuring the PMD of an optical fiber under test (FUT). A polarization-sensitive optical time domain reflectometer (POTDR) is used to inject into the FUT and from a proximal end thereof, a test signal comprising a series of repeated light pulses and detecting a corresponding polarization-analyzed return light signal coming back from the optical fiber and representing back-reflected light from a light reflector connected to a distal end of the FUT, said return light signal comprising repeated reflected light pulses. The plurality of polarization-sensitive acquisitions defines at least one pair of acquisitions performed with mutually different but closely-spaced wavelengths and substantially the same state of polarization (SOP), a center of said wavelengths defining a center wavelength for said at least one pair. The process may be repeated for a plurality of pairs of acquisitions performed with at least one of a plurality of mutually-different center wavelengths and a plurality of mutually-different states of polarization (SOP). For each said acquisitions, respective amplitudes of at least part of the repeated reflected light pulses are averaged so as to obtain an averaged reflected power. The PMD is obtained by, for each said pairs of said acquisitions, computing a value of a difference between the two averaged reflected powers corresponding to said pair, followed by the mean-square value of computed values of difference over said at least one of a plurality of mutually-different center wavelengths and a plurality of mutually-different states of polarizations (SOPs) and, from said mean-square value, calculating a value of the PMD for the optical fiber under test.

The invention discloses an optical fiber polarization characteristic detection method and device based on sound waves, and the method comprises the steps: enabling a laser device to emit a laser beam to enter an optical fiber coupler through an aperture diaphragm, a polarizer and a semi-reflecting and semi-transmitting mirror in sequence, and enabling the optical fiber coupler to divide the laser beam into a first light beam and a second light beam; the first light beam enters the first Faraday rotating mirror through the first optical fiber; the second light beam enters a second Faraday rotating mirror through a second optical fiber; the first optical fiber is a bare optical fiber, and the second optical fiber is tightly wound on the part body; reflected light of the first Faraday rotating mirror and the second Faraday rotating mirror returns along an original light path and is coupled by the optical fiber coupler to reach the semi-reflecting and semi-transmitting mirror; the sound signal is played to the second optical fiber tightly wound on the part body, and the first optical fiber is subjected to silencing treatment at the same time; and the semi-reflecting and semi-transmitting mirror reflects the returned coupled reflected light to the polarization analyzer to obtain polarization information. The method is used for detecting the influence of the sound wave frequency on the polarization characteristic of the optical fiber, and the accuracy of optical path transmission is ensured.

A system for providing advanced characterization of an optical fiber span is based upon the use of a pair of optical time domain reflectometers (OTDRs), located at opposing end terminations of the span being characterized. Each OTDR performs standard reflectometry measurements and transmits the resulting OTDR trace to monitoring equipment in a typical manner. The pair of OTDR traces is thereafter combined in a particular manner (“stitched together”) to create an OTDR trace of the entire fiber span (essentially doubling the operational range of prior art OTDR measurement capabilities). The transmit portion of one OTDR may be paired with the receive portion of the other OTDR, with time-of-light measurements (or signal loss measurements) used to determine optical path length and / or optical signal loss of the span. Using a multi-wavelength light source in the paired transmit / receive arrangement allows for a characterization of chromatic dispersion of the span.

A fiber rotator system includes a clamp assembly and a fiber rotator assembly for aligning multiple optical fibers. The clamp assembly has a base with fiber channels, fiber clamps, and a guide assembly. The fiber rotator assembly includes a linear actuator and wheel clamps, each aligning with a fiber base channel. Each fiber clamp includes a jaw, connecting rod, spring, and handle, while each wheel clamp includes a linear actuator contactor, wheel jaw, fiber channel rod, and wheel guide. A fiber detection and alignment system analyzes fiber end faces and provides alignment data to a fiber rotator controller. In operation, each wheel clamp contacts and rotates with the linear actuator. The fiber rotator controller selectively engages and disengages the fiber clamps and wheel clamps to iteratively rotate and secure fibers until all fibers are aligned. The system scalably automates alignment of multiple polarization maintaining (PM) fibers with high precision.

A fiber-sensing apparatus employs coherent dual-polarization MIMO sensing of backscattering light to monitor disturbances along an optical fiber. The apparatus switches to a self-calibration mode of operation to estimate polarization gain imbalances and / or linear signal distortions at the transmitter and the receiver. The polarization gain imbalances and / or the linear distortions are compensated for in a fiber sensing mode of operation.

The invention provides an optical fiber polarization mode dispersion distributed measurement method and system, and the method comprises the steps: enabling pulse polarized light to enter a to-be-measured optical fiber with unknown parameters for transmission, and enabling the polarization state of the pulse polarized light to randomly change at different positions of the to-be-measured optical fiber when the pulse polarized light is transmitted in the to-be-measured optical fiber due to a birefringence effect; detecting the polarization state of Rayleigh scattering light of the pulse polarized light, and constructing a polarized light time domain reflection curve; effective features of the polarized light time domain reflection curve are extracted and input into a pre-trained machine learning model, a polarization mode dispersion prediction result of the to-be-measured optical fiber is obtained, and distributed polarization mode dispersion measurement is achieved; compared with a traditional distributed polarization mode dispersion measurement scheme, the method only needs to emit the detection pulse light once, is low in cost and high in precision, does not need to change the optical signal polarization state of the receiving end for multiple times, is simple in system and convenient to install, and effectively improves the measurement efficiency of distributed polarization mode dispersion.

An optical measurement system in which a coherent light source generates a light signal, and a launch stage receives the light signal from the light source and generates a test signal. The test signal is launched along an optical path. The launch stage includes a first IQ modulator for controlling the test signal. The optical measurement system further includes a local oscillator stage configured to generate a local oscillator signal, wherein local oscillator stage has a second IQ modulator for controlling the local oscillator signal. A detector stage of the system is configured to receive the local oscillator signal from the local oscillator stage and a scattered signal from the optical path, and interfere the local oscillator signal with the scattered signal. The optical measurement system is implemented with one or more photonic integrated circuits.

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.

There is provided a method of measuring the PMD of an optical fiber under test (FUT). A polarization-sensitive optical time domain reflectometer (POTDR) is used to inject into the FUT and from a proximal end thereof, a test signal comprising a series of repeated light pulses and detecting a corresponding polarization-analyzed return light signal coming back from the optical fiber and representing back-reflected light from a light reflector connected to a distal end of the FUT, said return light signal comprising repeated reflected light pulses. The plurality of polarization-sensitive acquisitions defines at least one pair of acquisitions performed with mutually different but closely-spaced wavelengths and substantially the same state of polarization (SOP), a center of said wavelengths defining a center wavelength for said at least one pair. The process may be repeated for a plurality of pairs of acquisitions performed with at least one of a plurality of mutually-different center wavelengths and a plurality of mutually-different states of polarization (SOP). For each said acquisitions, respective amplitudes of at least part of the repeated reflected light pulses are averaged so as to obtain an averaged reflected power. The PMD is obtained by, for each said pairs of said acquisitions, computing a value of a difference between the two averaged reflected powers corresponding to said pair, followed by the mean-square value of computed values of difference over said at least one of a plurality of mutually-different center wavelengths and a plurality of mutually-different states of polarizations (SOPs) and, from said mean-square value, calculating a value of the PMD for the optical fiber under test.

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.

The invention provides an optical measurement system. The optical measurement system comprises a coherent light source configured to generate a light signal, and a launch stage configured to receive the light signal from the light source and generate a test signal and launch the test signal along an optical path. The launch stage includes a first IQ modulator for controlling the test signal. The optical measurement system further comprises a local oscillator stage configured to generate a local oscillator signal, wherein local oscillator stage comprises a second IQ modulator for controlling the local oscillator signal. A detector stage of the system is configured to receive the local oscillator signal from the local oscillator stage and a scattered signal from the optical path, and interfere the local oscillator signal with the scattered signal. The optical measurement system is implemented with one or more photonic integrated circuits.

A line monitoring system may include a laser source to launch a plurality of pulsed probe signals; an optical transmission system, comprising a plurality of loopbacks, to receive the plurality of pulsed probe signals, and direct the plurality of pulsed probe signals through the plurality of loopbacks. The system may include a receiver to receive a plurality of return signals, derived from the plurality of pulsed probe signals from the transmission system, and a perturbance detection system, coupled to the receiver, to measure a phase difference between a polarization of a pair of return signals of the plurality of return signals. The pair of return signals may be received from a pair of loopbacks of the plurality of loopbacks, from a first loopback and a second return signal from a second loopback. The perturbance detection system may determine a location of a perturbation, based upon the phase difference.

A cable identification system is provided. The cable identification system may include a laser pulse generator configured to emit laser pulses into the first optical-fiber cable segment. The cable identification system may include a polarization disturbance device configured to induce a change in polarization of a second optical-fiber cable segment via changing a position of the second optical-fiber cable segment. The cable identification system may include a polarization detection device configured to determine measures of polarization based upon backscattered light received from the first optical-fiber cable segment when the second optical-fiber cable segment has different positions. The polarization detection device may be configured to determine whether the first optical-fiber cable segment is connected to the second optical-fiber cable segment based upon the measures of polarization.

To provide spatially resolved disturbance detection using a line monitoring system.SOLUTION: The line monitoring system may include: a laser source to launch a plurality of pulsed probe signals; and an optical transmission system, comprising a plurality of loopbacks, to receive the plurality of pulsed probe signals, and direct the plurality of pulsed probe signals through the plurality of loopbacks. The system may include a receiver to receive a plurality of return signals, derived from the plurality of pulsed probe signals, from the transmission system, and a disturbance detection system coupled to the receiver and used to measure a phase difference between a polarization of a pair of return signals of the plurality of return signals. The pair of return signals may be received from a pair of loopbacks of the plurality of loopbacks, a first loopback, and a second return signal from a second loopback. The disturbance detection system may determine a location of a disturbance, based upon the phase difference.SELECTED DRAWING: Figure 1

An accurate measurement method and apparatus are disclosed for shape sensing with a multi-core fiber. A change in optical length is detected in ones of the cores in the multi-core fiber up to a point on the multi-core fiber. A location and / or a pointing direction are / is determined at the point on the multi-core fiber based on the detected changes in optical length. The accuracy of the determination is better than 0.5% of the optical length of the multi-core fiber up to the point on the multi-core fiber. In a preferred example embodiment, the determining includes determining a shape of at least a portion of the multi-core fiber based on the detected changes in optical length.

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.

Birefringence in optical fibers is mitigated using optical frequency domain reflectometry (OFDR) having a coupling point optically connected to a reference arm with a first, single mode fiber segment and optically connected to a measurement arm having single mode optical segments and polarization maintaining optical segments. The measurement arm has a first optical circulator connected to the coupling point via a second, single mode fiber segment; a second optical circulator for sending optical radiation to a sensor; a single mode optical segment between the first optical circulator and the second optical circulator including a third, single mode fiber segment. The measurement arm has an outbound path including a first polarization maintaining optical segment between the first and second optical circulator for rotating a polarization of the optical radiation once relative to a second polarization maintaining optical segment between the first and second optical circulator.

The present invention relates to an all-fiber current transformer with self-diagnosis of optical path status and a self-diagnosis method. Before welding, the all-fiber current transformer with self-diagnosis of optical path status is used to diagnose and record the average value of polarization intensity of multiple cycles, which is stored in a register as the polarization intensity before welding; after welding, the all-fiber current transformer with self-diagnosis of optical path status is used to diagnose and record the polarization intensity of multiple cycles, which is compared with the polarization intensity before welding to obtain the deviation; if the deviation does not exceed the first threshold, the optical path state is normal, if the deviation exceeds the first threshold and does not exceed the second threshold, the current coefficient of the all-fiber current transformer is adjusted according to the polarization intensity after welding, if it exceeds the second threshold, an alarm signal is output and the fuse is re-broken. The present invention solves the problem that the existing all-fiber current transformer cannot diagnose the polarization characteristics of the optical path through the system, and meets the new requirements of the smart grid for improving the reliability and stability of the current measurement device.

This invention discloses a method and apparatus for detecting the polarization characteristics of optical fibers based on acoustic waves. The method includes: a laser beam emitted from a laser sequentially passes through an aperture stop, a polarizer, and a semi-reflective lens before entering an optical fiber coupler; the optical fiber coupler splits the laser beam into a first beam and a second beam; the first beam is incident on a first Faraday rotator mirror via a first optical fiber; the second beam is incident on a second Faraday rotator mirror via a second optical fiber; the first optical fiber is a bare fiber, and the second optical fiber is tightly wound around a component; the reflected light from the first and second Faraday rotators returns along the original optical path and is coupled through the optical fiber coupler to the semi-reflective lens; an acoustic signal is played onto the second optical fiber tightly wound around the component, while simultaneously muting the first optical fiber; the semi-reflective lens reflects the returned coupled reflected light to an analyzer to obtain polarization information. This invention is used to detect the influence of acoustic wave frequency on the polarization characteristics of optical fibers, helping to ensure the accuracy of optical path transmission.