Polarization Optical Time Domain Reflectometer Research Articles

Lightning Location Method Using Orthogonal Coded Polarization Optical Time-Domain Reflectometer in Optical Fiber Transmission

Lightning strike is one of the main factors affecting power transmission lines and may lead to broken strands and damage of transmission lines, resulting in abnormal power supply. To improve the accuracy of lightning location, this paper presents a polarization optical time-domain reflectometer (POTDR) lightning location method based on orthogonal coding technology. The lightning strike point can be located by detecting the state of polarization (SOP) mutation of Rayleigh backscattering in the POTDR system. The orthogonal coding technology is used to improve the distance and accuracy of POTDR lightning location. Through calculation and simulation analysis, the location accuracy is significantly improved at the same sensing distance compared with the ordinary POTDR lightning location method. The lightning strike location error can be limited to 200 m in 20 km sensing distance which meets the actual engineering needs. The results of this paper are important to improve the operation and maintenance efficiency of transmission lines and reduce maintenance costs in the power industry.

Enhanced-Reach Polarization Optical Time-Domain Reflectometry Technique for Fibre Optical Infrastructure Monitoring

Abstract This interdisciplinary research is focused on constructing and demonstrating enhanced-reach polarization optical time-domain reflectometer (POTDR) for monitoring single-mode fibre optical communication lines. An optical signal state of polarization measurements enables several new possibilities for real-time monitoring solutions in fibre optics. However, there is no commercial equipment available to determine the location in fibre optical cable where the light polarization state changes. The authors present a monitoring technique of an optical signal state of polarization based on reflected signal time-amplitude analysis with improved operation parameters, namely, timing resolution (2 to 3 ps RMS) and amplitude measurement resolution of nanosecond scale pulses (8 to 10 bits) for monitoring of fibre optical communication lines. Additionally, the demonstrated POTDR provides a considerable optical fibre line measurement reach of up to 40 km.

A POTDR System based on Dual Sensing Directions

In this paper, a new distributed fiber optic sensor system based on dual sensing directions by polarization optical time-domain reflectometer (POTDR) is proposed. Using a single POTDR scheme, the system is able to detect signals in the forward direction and backward direction simultaneously. It can detect more perturbations applied on the fiber simultaneously than a traditional POTDR. It can also improve the positioning accuracy of POTDR by judging the perturbations from both directions. The proposed method is cost effective and has good potential in the application of intrusion monitoring.

Theoretical assessment of the OTDR detector noise on plasma current measurement in tokamaks

In this paper, we propose a theoretical study dedicated to the assessment of plasma current measurement in magnetic confinement fusion reactors using a polarization optical time-domain reflectometer (POTDR) setup with a low-birefringence fiber used as the sensing fiber. We consider the general case of a non-uniform magnetic-field distribution along the sensing fiber. The numerical simulations, based on Jones formalism taking into account the OTDR noise, provide the measurement error as a function of the plasma current. The measurement performance is evaluated for an ITER-relevant sensor configuration. We demonstrate that a signal-to-noise ratio of 6dB, achievable in modern POTDRs, allows us to comply with the ITER requirements for plasma currents from 0 to 1MA, while for the 1 to 20MA range, the level is relaxed to 4dB.

Detection of two identical frequency vibrations by phase discrimination in polarization-OTDR

In this paper, a new detection method for two identical frequency vibrations along optic fiber is proposed, by discrimination of their phase relationship in polarization optical time-domain reflectometer (POTDR). A vibration on fiber would modulate its index and birefringence, then it can consequently change the state of polarization (SOP) of the scattering signal. However, multiple simultaneous vibrations at different positions would result in random fluctuating SOP of the scattering signal, which make them very difficult to be identified. In our proposed method, the phase of the vibration signal along the fiber is obtained by Fast Fourier Transform. Therefore, two vibration events with the same frequency could be distinguished effectively by using the pattern of the phase distribution. The principle of the method is analyzed in detail. Both simulation and experiment results are presented to demonstrate the validity and limitation of this method. It could be widely used for safety monitoring of long distance perimeters, electrical transmission line, and so on.

Distributed Fiber-Optic Sensors for Vibration Detection.

Distributed fiber-optic vibration sensors receive extensive investigation and play a significant role in the sensor panorama. Optical parameters such as light intensity, phase, polarization state, or light frequency will change when external vibration is applied on the sensing fiber. In this paper, various technologies of distributed fiber-optic vibration sensing are reviewed, from interferometric sensing technology, such as Sagnac, Mach–Zehnder, and Michelson, to backscattering-based sensing technology, such as phase-sensitive optical time domain reflectometer, polarization-optical time domain reflectometer, optical frequency domain reflectometer, as well as some combinations of interferometric and backscattering-based techniques. Their operation principles are presented and recent research efforts are also included. Finally, the applications of distributed fiber-optic vibration sensors are summarized, which mainly include structural health monitoring and perimeter security, etc. Overall, distributed fiber-optic vibration sensors possess the advantages of large-scale monitoring, good concealment, excellent flexibility, and immunity to electromagnetic interference, and thus show considerable potential for a variety of practical applications.

On-field distributed first-order PMD measurement based on pOTDR and optical pulse width sweep.

A method for PMD distributed localization and estimation based on polarization optical time domain reflectometer technique, pOTDR and pulse width sweep is used on-field for the first time. The method consists in launching light pulses with variable widths in an optical fiber under test and then analyzes the Rayleigh backscattered signal spatial power distribution after passing through a polarizer. Both localization and PMD magnitude are function of OTDR pulse width and can be obtained from the ripple analysis, enabling the characterization of the fiber links.

Influence of optical pulse width on the perturbation detection performance of polarization-optical time domain reflectometer

The influence to the sensing performance of polarization optical time domain reflectometer (POTDR) by increasing the optical pulse width is analyzed based on wave-plate model and Muller matrices. Simulation and experimental results show that the ability of POTDR to sense external perturbation can be improved by increasing the pulse width of probe light, although the backscattered signal would be temporally depolarized. The depolarization effect is not a limitation to increase the pulse width to improve the signal-to-noise ratio for POTDR. The beat length of fiber can be taken as the critical value for the increase of pulse width.

OFS research over the last 10 years at CQU & UESTC

This article reviews my new optical fiber sensing (OFS) research activities in China for the last ten years at Chongqing University and University of Electronic Science and Technology of China, since I returned from UK in 1999. The research progress in long period fiber gratings (LPFGs), distributed fiber sensing systems and microfiber sensors is introduced. For LPFGs, the processing method with high-frequency CO2 laser pulses types of LPFGs fabricated and the related applications for both optical sensing and optical communication are described. For distributed fiber sensing systems, the fiber-optic polarization optical time domain reflectometer (POTDR), fiber-optic phase-sensitive optical time domain reflectometer (Φ-OTDR) and Brillouin optical time-domain analyzer (BOTDA) are developed, respectively. For microfiber sensors, we mainly focus on the knot resonator and its application for sensing of the refractive index and acceleration, etc.

Properties of polarization evolution in spun fibers

We study the properties of polarization evolution in sinusoidally spun fibers. It is found that, similar to linear birefringent fibers, the evolution of the state of polarization exhibits periodicity, which can be measured by distributed measurement, such as those made with a polarization optical time domain reflectometer. The spatial period is linked with the spin parameters and fiber beat length in a simple equation. In combination with a previous finding, it is shown that the spatial period is uniquely related to spun-fiber polarization mode dispersion. This suggests that distributed fiber polarization mode dispersion can be determined throughthe measurement of the spatial period obtained in a distributed measurement.

Polarization mode dispersion mapping in optical fibers with a polarization-OTDR

We describe a technique for the measurement of the polarization mode dispersion distribution along an optical fiber link based on a polarization optical time-domain reflectometer technique setup. This technique does not require the complete measurement of the polarization state of the backscattered signal. We report results performed on different types of fibers: standard step index, dispersion shifted, and dispersion compensating fibers.

Measurement of the spatial distribution of birefringence in optical fibers

We describe a technique for the measurement of the birefringence spatial distribution in a single-mode optical fiber with a resolution of 1 m. This technique is based on a polarization optical time-domain reflectometer using a rotary linear polarizer. We report results performed on different types of fibers: standard step-index and dispersion shifted fibers.

Distributed PMD measurement with a polarization-OTDR in optical fibers

This paper presents a new method for the measurement of distributed polarization mode dispersion (PMD) in optical fibers. This method uses a polarization optical time-domain reflectometer (P-OTDR), and is based on a measurement of the degree of polarization of the backscattered light as a function of distance in the fiber. Both the average and the statistics of the degree of polarization are used to estimate the two relevant parameters for measuring PMD, namely, the beat length and the coupling length. At present, our P-OTDR gives qualitative results only. However, it enables to distinguish between high and low PMD sections in a long fiber link. This should already have practical applications, in particular for the characterization of installed fibers.

Measurement and analysis on polarization properties of backward Rayleigh scattering for single-mode optical fibers

Fluctuation components on a backward Rayleigh scattered signal measured by the polarization optical time domain reflectometer (POTDR) have been investigated in detail by means of the least squares method and the power spectra. As a result, it is revealed that the fluctuation component for the single-mode optical fibers is attributable to the inherent polarization beat length determined by the difference of the phase velocities between the orthogonal e HE 11 and o HE 11 modes. The power spectrum of the fluctuation is sharply peaked at the Fourier frequency determined by the polarization beat length of approximately 15 m, which is in good agreement with the analysis. The utilization of the power spectrum presents a new method to diagnose the polarization properties along the optical fiber.