Polarization Mode Dispersion Measurement Research Articles

Improving the accuracy of the wavelength-scanning technique for PMD measurements

An improvement of the wavelength-scanning polarization mode dispersion (PMD) measurement technique is presented. It consists in the evaluation of the level crossing density for three or more levels, instead of only one. Experimental results show that measurement uncertainty can be reduced more than 40%.

Rotating-wave-plate Stokes polarimeter for differential group delay measurements of polarization-mode dispersion

We present a description and detailed uncertainty analysis of a polarization-mode dispersion (PMD) measurement system that uses the Jones matrix eigenanalysis measurement technique based on a rotating-wave-plate Stokes polarimeter. The uncertainty of the system is 3.2 fs (approximately 95% confidence interval) and is due primarily to PMD in the fiber leads of the measurement system.

Effect of Polarization Mode Coupling on Extrema Counting Fixed Analyzer PMD Measurement Method

We describe the effect of polarization mode coupling in the single-mode optical fibers on the extrema counting fixed analyzer (FA) polarization mode dispersion (PMD) measurement method. We define the polarization mode coupling coefficient for the over (or under) estimation which occurs with the FA method. We investigate the polarization mode coupling coefficient experimentally by comparison with the air-path (cross-correlation) type interferometric PMD measurement method. Moreover, we discuss the polarization mode coupling experimentally as well as analytically by using pseudo-polarization mode coupling which we obtained by splicing highly birefringent (B≅4.5×10−4) polarization maintaining fibers (PMFs) with the random splice angles. The results show that the PMD τ of the single-mode optical fibers which has random polarization mode coupling can be approximated by multiplying the PMD τ obtained using the FA method with the random polarization mode coupling coefficient k≅0.82.

Continuous-wave backreflection measurement of polarization mode dispersion

Experimental results of continuous-wave polarization mode dispersion (PMD) measurements are presented. The proposed technique is based on the backscattered signal given by the Fresnel reflection at the fiber far-end. Experimental statistical distribution of the differential group delay of the round-trip is reported. It presents a Rayleigh distribution whose mean value is simply related to the fiber mean differential group delay. Finally, the statistical distribution of the round-trip dispersion vector is found experimentally and numerically. The proposed method can be easily used for one-end measurement of PMD in installed optical cables.

Measurement of polarization mode dispersion in single mode fibre

Polarization mode dispersion (PMD) in fibre seriously limits the high-capacity optical fibre communication system. The measurement of PMD was realized by three methods — wavelength scanning method, modified OTDR method and modified York S-38 dispersion meter method. Different types of fibres have been measured using the above three methods and the results have been found to be consistent. Finally, we also found that the measured results of longer non-polarization-maintaining fibre satisfied the Maxwellian probability density function and the results of polarization maintaining fibre were derived.

Field Measurements of Polarization Mode Dispersion

Polarization mode dispersion (PMD) measurements are presented for a sample of installed optical fibers. High PMD values are fairly common, with 9 of the 71 fibers having PMD coefficients above 0.3 ps km1 2. The results are analyzed in terms of the age of the fibers and the type of cabling. Measurements are presented for a number of concatenated fiber links, and the results show that the PMD value of the link is approximately equal to the square root of the sum of the squares of the PMD values of the individual fibers.

A novel method for measuring polarization-mode dispersion using four-wave mixing

A method for measuring polarization-mode dispersion (PMD) on fiber links using four-wave mixing (FWM) generation is presented. This method uses a probe signal to analyze the signal polarization state via FWM generation. The FWM power transfer function is derived in terms of the Stokes parameters, and is validated using both simulated and experimental results. Based on this transfer function, PMD measurements are presented that agree well with the actual PMD values. Compared to the traditional frequency-domain methods, this new method does not require a motionless condition for the measurement apparatus.

Single-end polarization mode dispersion measurement using backreflected spectra through a linear polarizer

Routine characterization of polarization mode dispersion of single-mode fibers in installed cables requires simple and fast techniques. All standardized techniques use both fiber ends, one connected to the optical source and the other one for signal detection. Clearly, this causes several drawbacks in field tests because the two fiber ends are usually far from each other. Among standardized techniques, the fixed-polarizer method (also called wavelength scanning method) is one of the simplest to implement. In this work we present a new single-end measurement scheme based on the fixed polarizer method applied to the signal backreflected by the fiber far-end. We report analytical equations and numerical solutions that permit to calculate the mean value of the differential group delay measuring the crossings and/or extreme densities of the spectrum transmitted through a linear polarizer. We also show that the mean value of the differential group delay can be calculated using the Fourier transform of the detected signal. Finally, experimental results on cascades of single-mode step-index fibers confirm the robustness and easiness of our proposal for polarization mode dispersion measurements.

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.

Tests of a two-photon technique for measuring polarization mode dispersion with subfemtosecond precision

An investigation is made of a recently introduced quantum interferometric method capable of measuring polarization mode dispersion (PMD) on sub-femtosecond scales, without the usual interferometric stability problems associated with such small time scales. The technique makes use of the extreme temporal correlation of orthogonally polarized pairs of photons produced via type-II phase-matched spontaneous parametric down-conversion. When sent into a simple polarization interferometer these photon pairs produce a sharp interference feature seen in the coincidence rate. The PMD of a given sample is determined from the shift of that interference feature as the sample is inserted into the system. The stability and resolution of this technique is shown to be below 0.2 fs. We explore how this precision is improved by reducing the length of the down-conversion crystal and increasing the spectral band pass of the system.

Local birefringence measurements in single-mode fibers with coherent optical frequency-domain reflectometry

Measurements of intrinsic and induced birefringence of optical fibers are performed at 1550 nm using the optical frequency-domain reflectometry technique. The experiment confirms the theoretical analysis, which predicts the appearance of oscillations on the detected Rayleigh backscattering intensity, with periods equal to the polarization beat length L/sub b/ and to L/sub b//2. Polarization mode-coupling length values are obtained from local birefringence and polarization mode dispersion measurements.

Polarization mode dispersion measurement using a Sagnac interferometer and a comparison with the fixed analyzer method

Polarization mode dispersion measurement using a Sagnac interferometer is compared with the well-known fixed analyzer technique both theoretically and experimentally. It is shown that in the case of weak mode coupling in the fiber the Sagnac interferometer method is equivalent to the fixed analyzer method but gives better readability of the measured optical spectrum. For strong mode coupling, we develop a theory that relates the differential group delay to the number of mean-level crossings in the measured spectrum.

Correction To The Journal Of Lightwave Technology April 1998 Table Of Contents

Summary form only, as follows. The topical heading of "Fibers" was omitted from JOURNAL OF LIGHTWAVE TECHNOLOGY's April 1998 Table of Contents. The following papers, which were included under "Systems" should have been listed under "Fibers." 1) "Corrections to Fixed Analyzer Measurements of Polarization Mode Dispersion" by P.A. Williams and C.M. Wang. 2) "Signal-Induced Refractive Index Changes in Erbium-Doped Fiber Amplifiers" by M. Janos and S.C. Guy. 3) "Generating Mechanism of Maintaining Force for Optical Fiber Installed in Ferrule Hole" by M. Takahashi. 4) "Simulation and Characteristics of Long-Period Fiber Bragg Grating Coherence Spectrum" by Y. Zhao and J.C. Palais. 5) "Nd-Doped Double-Clad Fiber Amplifier at 1.06μm" by T. Miyazaki, K. Inagaki, Y. Karasawa, and M. Yoshida. 6) "Improved Design of APC Optical Connectors with Slanted Angle of 12° for Dispersion Shifted Optical Fiber" by M. Takahashi.

Corrections to fixed analyzer measurements of polarization mode dispersion

We report computer simulation results of polarization mode dispersion (PMD) measurements using the fixed analyzer technique. We find a new value for the polarization mode coupling factor of 0.805 (a 2% difference with the old value of 0.824). Systematic biases due to sampling density and extrema thresholding are quantified (6-12% for typical measurement conditions), and a simple correction algorithm is presented which removes the effects of these biases within /spl plusmn/1.7%.

Measurement of polarization mode dispersion in systems having polarization dependent loss or gain

The principal states of polarization and their propagation characteristics are analyzed for both unitary and nonunitary optical systems in terms of the complex plane representation of polarization. A new method for the estimation of the polarization mode dispersion of the system is proposed together with experimental and simulation results.

Aspects of PMD Measurements

This paper describes polarization mode dispersion (PMD) measurements of long standard and advanced single-mode fibers, uncabled on bobbins and in cables which are installed in test and Telekom service links. We will present measurement set-ups representing the two complementary aspects of PMD in the time and frequency domains. We will show that both measuring principles are complementary and necessary to describe the phenomenon of polarization mode dispersion. We will discuss measurement results giving an impression of the order of magnitude of the PMD effect. Measurements of optical components of transmission systems are important and will be presented. Measurements on hauls with optical amplifiers (EDFAs) using interferometric methods are problematic due to the large ASE power of the EDFAs. A solution of this problem will be discussed.

Interferometric polarization mode dispersion measurements with femtosecond sensitivity

The standard interferometric measurement technique for polarization mode dispersion (PMD) measures the cross correlation of the electromagnetic field at the output of the fiber or optical device under test when a broadband light source is used. The sensitivity (smallest measurable PMD delay) of this technique is limited by the coherence time of the light source. In this contribution, we critically analyze extensions of the interferometric technique to lower values and present a new extension which provides a sensitivity of a few femtoseconds.

How accurately can one measure a statistical quantity like polarization-mode dispersion?

The differential group delay (DGD) due to varying local birefringence and random polarization mode coupling is a statistical quantity. Its value at any wavelength fluctuates in time. At any given moment it is wavelength sensitive. Hence, polarization-mode dispersion can only be defined as a mean or rms value of the DGD. All measurements of polarization-mode dispersion involve thus an averaging over a finite sample set. Consequently, all measurements are intrinsically of limited accuracy. We present analytical formulae and numerical data characterizing this intrinsic limitation common to all measurement techniques.

Optimized Polarization Mode Dispersion Measurement with “π-Shifted” White Light Interferometry

The interferometric method, based on white light interferometry, is a powerful tool to measure the polarization mode dispersion (PMD) of fibers. We propose an improved setup, based on a Michelson interferometer where a λ/4 waveplate is inserted in one arm of the interferometer. We show both theorically and experimentally that this “π-shifted” configuration is optimized for PMD measurements and that the simplicity of the set up makes it an ideal tool for fast analysis of the PMD of long fiber cables.

Polarisation mode dispersion: Large scale comparisonof Jones matrix eigenanalysisagainst interferometric measurement techniques

A comparison of polarisation mode dispersion (PMD) measurements between the Jones matrix eigenanalysis and the interferometric technique is presented. A large range of PMD delays between 0.1 and 20 ps have been taken into account. The results show a very good agreement in the range up to 5 ps. The slope of a linear fit deviates <3 % from unity. Taking into account the values in the higher range up to 20 ps, a deviation of 13% from unity is obtained.