129 results about "Optical time-domain reflectometer" patented technology

The invention relates to a phase-sensitive optical time domain reflectometer based on multi-frequency reference switching. Continuous laser generated by a continuous laser is divided into a local path and a detection path through an optical coupler; the local path is input to the polarization coherent receiving module, the detection path is incident to a light intensity modulator driven by the signal generation circuit module, and the light intensity modulator is converted into a multi-frequency pulse laser sequence with intensity modulation; the multi-frequency pulse laser sequence enters the sensing optical fiber to be measured through the optical circulator; generated Rayleigh backscattered light and local continuous laser are subjected to beat frequency coherent receiving in a polarization coherent receiving module through a circulator; and the signal acquisition circuit adopts a demodulation algorithm to compensate phase drift and sensitivity difference of detection pulse demodulation signals with different frequencies so as to realize dynamic strain sensing. Compared with the prior art, the phase drift and the sensitivity difference between the frequencies are extracted to realize the compensation of the interleaved signals, and the method does not depend on the fixed reference frequency, so that the robustness and the adaptability of the system in a complex environment are remarkably enhanced.

The invention relates to an electric power communication optical fiber fault monitoring and visualization method and system, and belongs to the technical field of optical fiber communication monitoring, and the method comprises the following steps: carrying out the real-time monitoring of an electric power communication optical fiber through a non-intrusive monitoring system, collecting an optical power signal in real time, and constructing an optical fiber resource database; when the non-intrusive monitoring system detects that optical power attenuation exceeds a preset threshold value, an optical time domain reflectometer OTDR is started to perform intrusive detection on an abnormal optical fiber, and an OTDR echo curve is obtained; extracting a composite feature vector of an OTDR echo curve, and identifying a fault type through a multi-stage fusion algorithm in combination with historical fault record data; according to the OTDR detection point coordinates, the optical path distance and the geographic information data, the position of a fault point is calculated, and the optical fiber topology, the position of the fault point and the fault type of the fault point are displayed in a visual interface. According to the invention, accurate fault identification and quick response are realized, and the operation and maintenance efficiency is improved.

The invention relates to a phase-sensitive optical time domain reflectometer based on a parallel frequency division multiplexing sequence. Continuous laser is divided into a local path and a detection path through an optical coupler; the local path is input to the polarization coherent receiving module, the detection path is converted into a pulse laser sequence with intensity modulation through a light intensity modulator driven by a radio frequency signal provided by the signal generation circuit module, and the radio frequency signal is composed of two frequency division multiplexing sequences with difference; the pulse laser sequence enters the sensing link to be measured to generate Rayleigh backscattered light, and the Rayleigh backscattered light and local continuous laser are subjected to beat frequency coherent receiving through a circulator; and the signal acquisition circuit is used for sampling and analyzing the interference signal, and performing frequency domain comparison on an interleaving result of the two frequency division multiplexing pulse sequences to eliminate a harmonic frequency and retain a real strain signal frequency. Compared with the prior art, the non-harmonic strain signal measurement is realized, the high-frequency response performance and the high-precision strain measurement capability are excellent, and meanwhile, the long-distance coverage capability is also realized.

The invention relates to an optical time domain reflectometer and a control method of the optical time domain reflectometer, and relates to the technical field of photoelectricity. The optical time domain reflectometer OTDR comprises a single photon detector, and the OTDR is used for being connected with an optical fiber to be measured; the OTDR is further used for sending a plurality of detection signals to the optical fiber to be detected in sequence and receiving a plurality of detection echo signals from the optical fiber to be detected in sequence, and the detection echo signals are used for indicating the transmission state of the same section of transmission area in the optical fiber to be detected; performing amplitude reduction processing on each detection echo signal at a certain time interval to obtain a processed detection echo signal; the positions, corresponding to the same section of transmission area, of the signal sections subjected to amplitude reduction processing in the different processed detection echo signals are not completely the same; each processed detection echo signal is subjected to photoelectric conversion based on the single-photon detector to obtain a first electric signal, a first OTDR oscillogram is output based on the multiple first electric signals, and the first OTDR oscillogram is used for indicating the transmission state of the same section of transmission area. Therefore, the problem of OTDR curve distortion can be solved.

The invention relates to the technical field of data processing, and discloses a gateway service integrated management method and system based on an FTTR demand. The method comprises the following steps: carrying out topology scanning on a test signal of an optical time domain reflectometer to obtain a room-level FTTR topology mapping table, carrying out feature extraction on service traffic of each room according to deep packet inspection to obtain a room function identification tag library, and carrying out attenuation compensation on a corresponding room optical port by an optical power meter to obtain an FTTR link quality evaluation matrix, and bandwidth allocation is carried out through a reinforcement learning algorithm to obtain a room-level QoS strategy configuration set, and building data interaction is carried out based on an MQTT protocol to obtain an FTTR gateway service integrated management scheme. According to the invention, the intelligent level of FTTR network room-level management and the resource allocation efficiency are improved. According to the invention, the real-time performance of optical fiber link quality monitoring and the collaboration of building network management are improved.

The invention discloses a phi-OTDR (Optical Time Domain Reflectometer) vibration signal classification method based on multi-scale residual convolution and a bidirectional long-short-term memory network, relates to the technical field of phase-sensitive optical time domain reflectometer vibration sensing, and solves the problems of insufficient feature extraction, single model fusion mechanism, poor system real-time performance and the like of an existing phi-OTDR vibration signal classification method. The method is realized through the steps of a multi-scale deep convolutional network, a bidirectional long-short term memory network, a cross attention fusion module, a learnable gating mechanism and the like. A cross attention fusion module is adopted, association between spatial features and time sequence features is dynamically established in a double-path network, feature interaction and information coupling are deepened, and the sensing ability of the model to key information is remarkably improved. Meanwhile, the fusion proportion of the multi-path features is adaptively adjusted according to the actual distribution of the input features, background noise interference is effectively suppressed, and the robustness and discrimination performance of the model are enhanced. Accurate identification and classification of external vibration signals are realized.

The invention provides a phase-sensitive optical time domain reflectometer system and method, and the system comprises a first polarization-maintaining coupler which is used for dividing laser generated by a DC laser, and obtaining first laser and second laser; the optical fiber measurement front-end module is used for processing the random signal through pulse shaping and multi-carrier modulation technologies to generate an electric signal, and sequentially performing modulation, amplification, Rayleigh scattering and amplification on the first laser after the electric signal is generated to obtain amplified Rayleigh backscattered light; the second polarization-maintaining coupler is used for dividing the second laser to obtain third laser and local oscillation light; the delay optical fiber is used for processing the third laser to obtain delay light; the third polarization-maintaining coupler is used for combining the delayed light and the amplified Rayleigh backscattered light to obtain combined light; the receiver is used for processing the combined light and the local oscillation light to obtain multiple paths of target electric signals; and the oscilloscope is used for processing multiple paths of target electric signals through low-pass and high-pass filters and a phase noise compensation algorithm so as to determine power and phase distribution. The system cost can be reduced.

The invention discloses a composite hose structure for fuel gas transmission, and relates to the technical field of fuel gas transmission and distribution equipment, the composite hose structure comprises a dual-mode quick sealing assembly, dual-mode monitoring is formed by an FBG sensor, a phase-sensitive optical time domain reflectometer and a carbon tube composite filament, the FBG sensor can capture fine strain of a reinforced fiber layer in real time, and the phase-sensitive optical time domain reflectometer can capture the fine strain of the reinforced fiber layer in real time; the phase-sensitive optical time domain reflectometer detects and captures stress waves generated by crack propagation in a material through broadband sound waves, early recognition of millimeter-level damage in a pipe is achieved, grids woven by carbon tube composite filaments are utilized, continuity of the grids is monitored in real time through alternating-current impedance measurement, and the detection accuracy of the millimeter-level damage in the pipe is improved. When local grid resistance is increased due to breakage of the reinforced fiber layer, a micro-damage area can be accurately positioned, when leakage occurs, the memory alloy spring receives an electric signal monitored by a dual-mode, then axial thrust is generated to push the outer side of the fluororubber sealing ring, the fluororubber sealing ring expands in the radial direction under the thrust action of the memory alloy spring, and the leakage is prevented. And rapid and effective mechanical hard sealing is realized.

The invention relates to the technical field of optical fiber sensing, in particular to a dual-channel information fusion vibration positioning device and method based on a dual-k method, and aims to improve a traditional single-channel amplitude demodulation phi-OTDR (AD-phi-OTDR) system to obtain a device with a dual-channel phase-sensitive optical time domain reflectometer module. Firstly, vibration signals are collected through a dual-channel amplitude demodulation phi-OTDR system, then the optimal sampling number is designed through the relation between the vibration frequency and the sampling period, the time consumed by system vibration positioning is shortened, the operation efficiency of the system is improved, then vibration positioning is conducted through a dual-k method, and finally vibration is judged through dual-channel information fusion. According to the invention, the authenticity of the signal is improved through dual-channel cross validation. And a dual-channel data fusion mechanism is used for effective discrimination, so that the anti-interference performance of the system is improved, and the reliability of vibration signal discrimination is further improved.

The invention provides an optical fiber detection method and system for an optical time domain reflectometer, and relates to the technical field of power grids. According to the invention, the multi-wavelength backscattering signal of the optical fiber link to be detected is acquired, preprocessed and converted into the sample to be detected containing the multi-wavelength one-dimensional waveform data and the multi-wavelength two-dimensional diagram data at the same time, so that the sequence characteristic of the light intensity of each wavelength changing along with time is reserved; and spatial features of correlation and structural information between wavelengths can be reflected through data conversion construction, and multi-dimensional and structured representation of optical fiber events is realized. And combined analysis and recognition are carried out by combining a fault recognition model, and a time sequence rule in a one-dimensional waveform and a spatial distribution mode in a two-dimensional diagram are cooperatively mined, so that deep fusion and intelligent analysis of optical fiber fault spatial-temporal characteristics are realized, and the recognition capability of a complex fault mode is improved. The technical problem of low accuracy of optical fiber fault detection with a single wavelength at present is solved, and the accuracy and reliability of optical cable line fault detection are improved.

The invention discloses an interference fading point compensation method for a coherent phi-OTDR (Optical Time Domain Reflectometer), which comprises the following steps of: identifying an interference fading point on the basis of complex envelope characteristics obtained by coherent receiving and I / Q (Input / Output) demodulation, and performing interpolation reconstruction on a fading point echo vector by using a neighborhood non-fading point on a complex plane, so as to recalculate a phase and a differential phase; therefore, phase demodulation failure and differential phase artifacts caused by fading can be suppressed. According to the method, on the premise of not increasing hardware transformation, differential phase artifacts and abnormal stripes caused by phase demodulation failure at a fading point are reduced, the stability of a differential phase result and event identifiability are improved, and relatively low calculation complexity is kept to adapt to offline or quasi-real-time processing.

The application provides a phase-sensitive optical time domain reflectometer, a measurement method and a readable storage medium, wherein a signal generation circuit of the phase-sensitive optical time domain reflectometer is configured to generate a radio frequency signal to drive an optical intensity modulator to modulate probe light, so that two groups of frequency division multiplexing sequences with differences can be used to synchronously detect a sensing optical fiber to be measured, a differential unfolding algorithm is combined to accurately solve a phase change amount in adjacent sampling intervals, and then demodulation results corresponding to different frequency parts are respectively unfolded to obtain unfolded phase results, so that the problem of large strain phase folding is solved and a large strain range is recovered, and further, the unfolded phase results are rearranged and combined in time sequence through time sequence interleaving processing of the unfolded phase results, so that a high sampling rate and a distortion-free reconstruction result are reconstructed, and therefore, the application can realize accurate measurement of high frequency response and large strain range dynamic strain.

The invention discloses an in-operation OPGW icing tension monitoring method based on a micrometeorological temperature demodulation BOTDR. The method comprises the following steps: measuring through a Brillouin optical time domain reflectometer to obtain OPGW Brillouin frequency shift data; calibrating a Brillouin frequency shift temperature sensitivity coefficient and a Brillouin frequency shift tension sensitivity coefficient of the OPGW by using the data of the microclimate icing monitoring terminal; according to the Brillouin scattering principle, all Brillouin frequency shifts are converted into Brillouin equivalent temperatures; the external environment temperature of the OPGW is measured through the micro-meteorological icing monitoring terminal and is defined as temperature data of the micro-meteorological icing monitoring terminal; calculating a difference value between the Brillouin equivalent temperature and the temperature data of the microclimate icing monitoring terminal; and when the temperature difference value is greater than or equal to the temperature measurement precision of the Brillouin optical time domain reflectometer, the icing tension is calculated. According to the invention, the Brillouin frequency shift temperature sensitivity coefficient and the Brillouin frequency shift tension sensitivity coefficient can be directly calibrated on line, and the calibration result and the icing tension monitoring result are more accurate.

The invention relates to a signal noise suppression system based on an optical time domain reflectometer, and the system comprises a transmitting unit which is used for generating an optical time domain reflection pulse signal with preset parameters according to control information; the testing unit is connected with the transmitting unit and the optical fiber to be tested and is used for injecting the received pulse signal into the optical fiber to be tested and guiding the reflected echo optical signal into the receiving unit; the receiving unit is connected with the testing unit and is used for receiving the echo optical signal and converting the echo optical signal into a digital signal, so that the data processing unit can receive and process the digital signal conveniently; and the data processing unit is respectively connected with the receiving unit and the transmitting unit and is used for carrying out range dynamic filtering processing according to the data signal transmitted by the receiving unit, storing the filtered signal and transmitting control information to the transmitting unit, so that the transmitting unit generates a pulse signal with a preset parameter according to the signal. The technical problems of signal broadening deformation and time delay, slow system operation, increased test blind area and the like in the prior art are solved.

The invention discloses a BOTDR (Brillouin Optical Time Domain Reflectometer)-based OPGW (Optical Fiber Composite Overhead Ground Wire) light icing identification method, which comprises the following steps of: firstly, establishing a thermal conduction model of an OPGW in a non-icing state and an icing state, and constructing a theoretical expression of an OPGW icing thermal hysteresis effect by utilizing a linear relation between Brillouin frequency shift and temperature; then, the Brillouin frequency shift distribution along the line is obtained through a BOTDR system, actually measured data is matched with a model calculation result, and the icing thickness and the distribution interval are obtained through a regularization least square inversion method. According to the invention, clear identification of the light icing section can be realized, and good stability can be maintained under different illumination radiation intensity conditions. The method is clear in mechanism, high in model precision and suitable for early icing identification and anti-icing and deicing early warning application of the long-distance OPGW line.

1. The name of this design product: Multifunctional Optical Time Domain Reflectometer (SW100). 2. Purpose of this product: This product is used to measure optical fiber length, optical fiber transmission attenuation, connector attenuation and fault location. 3. The key point of the design of this product lies in its shape. 4. The picture or photo that best illustrates the design points: three-dimensional picture.

A kind of distributed multi-parameter sensing system based on multi-core optical fiber, including laser, laser light source is sent to the signal generator input trigger pulse drive respectively with the signal input end of phase-sensitive optical time domain reflectometer based on Rayleigh scattering and its demodulation device, Raman optical time domain reflectometer based on Raman scattering and its demodulation device, Brillouin optical time domain reflectometer based on Brillouin scattering and its demodulation device are connected, the signal output end of phase-sensitive optical time domain reflectometer and its demodulation device, Raman optical time domain reflectometer and its demodulation device, Brillouin optical time domain reflectometer and its demodulation device is connected with the signal input end of multi-core optical fiber through multi-core optical fiber fan-in fan-out module;The present application utilizes the principle of space division multiplexing, each fiber core in optical cable as separate sensing channel carries out measurement and signal transmission;Multi-core optical fiber fuses three kinds of distributed optical fiber sensing systems together, realizes in-situ measurement and mutual compensation decoupling of temperature, strain and vibration, improves the measurement precision of sensing system.

1. Name of the product in this design: Optical Time Domain Reflectometer (Simplified Version). 2. Purpose of this design: For testing fiber optic signals. 3. The key design feature of this product is its shape. 4. The image or photograph that best illustrates the design's key points: a 3D model.

Methods and systems for referencing an optical power loss measurement (OPLM) system, and methods and systems for measuring an optical insertion loss of an optical device under test (DUT) using an OPLM system referenced as such. The herein-provided reflectometric one-cord referencing method combines the capabilities of an OPLM system with that of an Optical Time Domain Reflectometer (OTDR). A first test unit comprises an optical source that is used as the light source in the OPLM. A second test unit comprises a power meter which is used as the power meter in the OPLM measurement. Either the first or the second test unit comprises an OTDR acquisition device. The reflectometric one-cord reference measures the connector loss along the reference link using OTDR capabilities of the test unit(s). Once the power reference of the OPLM devices is obtained, the reflectometric one-cord reference method may determine the optical insertion loss of the DUT while eliminating the measured connector loss.

The invention belongs to the field of distributed optical fiber sensing and coding and decoding, and provides a Brillouin optical time domain reflection signal decoding method and system based on rising edge assistance. The rising edge assistance-based Brillouin optical time domain reflection signal decoding method comprises the following steps: acquiring a time domain coding response signal corresponding to a coding pulse sequence injected into an optical fiber by a Brillouin optical time domain reflectometer; performing discrete Fourier transform on the time domain coding response signal to obtain a frequency domain coding response signal; according to the signal increment and the duration of the rising edge of the time domain coding response signal, reconstructing a decoding function and replacing the decoding function in the frequency domain coding response signal with the reconstructed decoding function; the decoding function is a sequence formed by a decoding weight corresponding to each code element; and performing inverse discrete Fourier transform on the frequency domain coding response signal to obtain a decoded signal. According to the method, the signal-to-noise ratio of the decoded SpBS signal can be remarkably improved, and the Brillouin frequency shift (BFS) extraction precision is enhanced.

The invention provides a mine underground distributed optical fiber acoustic sensing system coupling construction method, and relates to the technical field of construction. Comprising the steps of sensing optical fiber routing design and optimal route and construction mode planning; carrying out base surface treatment and grooving at the included angle between the roadway bottom plate and the side wall; cleaning float coal in the groove, applying a coupling agent with a certain thickness on the bottom plate, and lightly pressing the sensing optical fiber into the coupling agent; covering the upper part of the optical fiber with a coupling agent until the groove is full, and applying pressure to ensure that the coupling agent is fully extruded to be tightly coupled with the coal (rock) body and the optical fiber; and finally, testing optical fiber loss by using an OTDR (Optical Time Domain Reflectometer), and carrying out field knocking detection by using a DAS host. According to the invention, the acoustic binding of the sensing optical fiber and the coal rock mass is realized through the two layers of high-damping coupling agents, and the transmission efficiency and the signal-to-noise ratio of a vibration signal are greatly improved; in addition, a quantifiable and verifiable construction process is provided, and consistency and reliability of monitoring data of different engineering sections are guaranteed.

The invention relates to the field of optical fiber pipeline monitoring, in particular to a safety monitoring method and equipment for an optical fiber pipeline and a medium, and the method comprises the steps that an unmanned aerial vehicle carries an optical time domain reflectometer and environment monitoring equipment to fly along the pipeline, and reflected light information and environment parameters such as temperature, humidity, air pressure and flight relative height are synchronously obtained. And after an initial leakage position is determined based on the reflected light information, an adaptive leakage position correction model is selected from a preset reference table according to the environmental parameters corresponding to the position. And the offset is calculated by substituting the environmental parameters into the correction model, and the target leakage position is obtained. According to the method, multi-source data fusion and a precise correction model are utilized, interference of environmental factors on positioning is effectively eliminated, the precision and reliability of optical fiber pipeline leakage positioning are remarkably improved, and the method is suitable for a pipeline safety monitoring scene in a complex environment.

The invention relates to an optical fiber link fault diagnosis method and device, computer equipment, a readable storage medium and a program product. The method comprises the following steps: acquiring a time domain power fluctuation characteristic of the optical fiber link through an intelligent optical module, and acquiring a space domain performance fluctuation characteristic of the optical fiber link through an optical time domain reflectometer; fusing the time domain power fluctuation feature and the space domain performance fluctuation feature to obtain a fused fluctuation feature; and determining a fault diagnosis result of the optical fiber link according to the fusion fluctuation characteristics. By adopting the method, the fault diagnosis efficiency of the optical fiber link can be improved.

The application provides a blind person discrimination device, system and method based on a distributed optical fiber sensing device.The device comprises an optical time domain reflectometer module, a signal preprocessing module, a signal cutting module, a signal feature extraction module and a signal classification module.The method provides a high recognition rate without video monitoring equipment and wearable sensing equipment, more comprehensively and effectively provides application support for the field of security and blind person travel, enhances the adaptability for different human body recognition, and identifies the source of the human body walking signal accepted by the current device, whether it is a visually impaired user or a normal user, so as to provide related services for the visually impaired user in the future.The long-time and short-time feature joint recognition mode is adopted in the feature extraction algorithm, and the accuracy is further improved.

The invention discloses an optical fiber fault diagnosis method and system based on an IMC-BiLSTM network model, and the method comprises the following steps: measuring an optical fiber through an optical time domain reflectometer, and obtaining original optical time domain reflectometer data corresponding to different fault types; preprocessing the original optical time domain reflectometer data to obtain preprocessed optical time domain reflectometer data; the preprocessed optical time domain reflectometer data is input into an IMC-BiLSTM network model for training, and a trained IMC-BiLSTM network model is obtained; using the trained IMC-BiLSTM network model to diagnose the data of the optical time domain reflectometer to be identified to obtain the type of the optical fiber fault and the diagnosis result; according to the method, the optical time domain reflectometer data is preprocessed, and based on training and identification of the IMC-BiLSTM network model, intelligent classification and diagnosis of optical fiber fault types are realized.

The invention discloses an optical fiber fault diagnosis method and system based on an SMC-BiLSTM network model, and the method comprises the following steps: measuring an optical fiber through an optical time domain reflectometer, and obtaining original optical time domain reflectometer data corresponding to different fault types; preprocessing the original optical time domain reflectometer data to obtain preprocessed optical time domain reflectometer data; the preprocessed optical time domain reflectometer data is input into an SMC-BiLSTM network model for training, and a trained SMC-BiLSTM network model is obtained; using the trained SMC-BiLSTM network model to diagnose the optical time domain reflectometer data to be identified, and obtaining the type of the optical fiber fault and the diagnosis result; according to the method, the optical time domain reflectometer data is acquired and preprocessed, and training and identification are performed based on the SMC-BiLSTM network model, so that intelligent diagnosis of optical fiber faults is realized.

The invention relates to the technical field of optical fiber event detection, and discloses a phi-OTDR event detection method, system and device and a medium, and the method comprises the steps: obtaining the optical fiber signal data of an original phase-sensitive optical time domain reflectometer, and carrying out the first processing; constructing a deep learning model based on the residual network, training the deep learning model by using the training set, evaluating the performance through the verification set, and adjusting hyper-parameters according to an evaluation result to optimize the model; and inputting the data after the first processing into a trained deep learning model based on a residual network to extract high-level features of the optical fiber signals, and performing event identification and classification according to the high-level features. According to the method, the problems that the current OTDR event detection signal is interfered in noise, the model is insufficient in tiny event extraction capability, and the deep learning model is slow in convergence speed and poor in generalization capability are solved, automatic and accurate identification of the optical fiber event is realized, and the efficiency and reliability of optical fiber fault diagnosis are greatly improved.

1. The name of the design product: optical time domain reflectometer (7 inches). 2. The use of the design product: the design product is used for testing optical fiber cable. 3. The design points of the design product: in shape. 4. The picture or photo that best shows the design points: perspective view.

The invention discloses a track zero calibration method of an optical time domain reflectometer and a related product, and the method comprises the steps that the optical time domain reflectometer emits a short pulse signal which sequentially passes through a reference optical fiber and an optical fiber to be measured, an original track curve corresponding to the short pulse signal is obtained, the reference optical fiber is arranged in the optical time domain reflectometer, and the reference optical fiber is arranged in the optical time domain reflectometer; the length of the reference optical fiber is greater than the spatial resolution of short pulse signal scanning; based on the original trajectory curve, determining reflected light power corresponding to the reference optical fiber; obtaining a first translation amount of the original trajectory curve based on the reflected light power corresponding to the reference optical fiber; and translating the original trajectory curve based on the first translation amount, completing calibration of a zero point, and obtaining an absolute loss trajectory curve corresponding to the to-be-measured optical fiber. Therefore, after zero calibration, the longitudinal axis value of the absolute loss trajectory curve can directly correspond to the absolute loss of each position of the optical fiber to be measured, and the trajectory curves of the same optical fiber at different moments can be conveniently compared, so that the readability of the trajectory curve is improved.

A method and system 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. 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). 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 SOPs, and a value of the PMD for the FUT is calculated therefrom.