![]() ![]() To measure the Jones matrix of a device, a stimulus optical field of linear polarization parallel to the x axis is first generated, and the resulting response unit vector h is measured through the device. Any Jones vector v can be completely specified by a magnitude, an absolute phase, and a A unit vector v which locates the SOP on the Poincare sphere. Therefore, this technique can be used to characterize fiber networks even when the phase delay through the fiber is drifting during the measurement. The restriction of time invariance applies only to the polarization transformation caused by the device, and does not include the absolute optical phase delay. The restriction of linearity precludes optical devices that generate new optical frequencies. Jones gave an explicit algorithm for experimentally determining the forward transmission Jones matrix T of an unknown linear, time-invariant optical device. The technique to be described suffers none of these limitations or disadvantages.Ģ Theory R. Measurement of the arc described by the output SOP on the Poincare sphere over a series of wavelengths, as in and, or measurement of the frequency derivatives of normalized Stokes vectors as in, would be difficult to automate because they produce erroneous results when a measurement SOP is near one of the PSP. ![]() The technique of reference, which relates a T to the density of extrema in the spectrum of transmission through the DDT in series with a polarizer, yields poor resolution in the variation of aT with wavelength and does not identify the PSP. Those based on changes in the auto- or cross-correlation of a low-coherence source must employ a wide-spectrum source in order to achieve good temporal resolution, making them unsuitable for measurement of devices whose PMD varies with wavelength. Several PMD measurement techniques have been reported. PMD is completely characterized by a wavelength-dependent, three-dimensional polarization dispersion vector, or equivalently by the specification of a pair of principal states of polarization (PSP) and a differential group delay a T as a function of wavelength. The physical mechanism that causes PMD may be localized and stable, as in the birefringent crystals in an optical isolator, or distributed and timevarying, as in the random perturbations in a single-mode fiber. PMD, which may limit transmission bandwidths in practical systems, is a fundamental characteristic of a network or device under test (DDT) that describes its propensity to split a narrow-band optical input pulse into two temporally separate output pulses according to state of polarization (SOP). Both the principal states of polarization and the group delay difference are measured as a function of optical frequency.ġ Introduction Thorough characterization of the optical components intended for high-speed transmission links requires accurate, repeatable measurement of polarization mode dispersion (PMD). A fast, automated system using a tunable laser and an accurate, real-time polarimeter affords temporal accuracy of approximately 2% down to a limit of several femtoseconds, as demonstrated by comparison with other techniques and comparison with known samples. We demonstrate for the first time that PMD in any linear, time invariant network can be completely characterized by eigenanalysis of Jones matrices measured at a series of discrete wavelengths, even for networks exhibiting polarization-dependent loss. Polarization mode dispersion (PMD), which can limit the bandwidth of optical transmission links, has been difficult to measure in a manner independent of human judgment, leading to difficulties in automating the measurement. Optical, fiber optics, photonic subsystems, incoherent, photonics, lightwave components Heffner Instruments and Photonics Laboratory HPL-92-63 May, 1992 Automated Measurement of Polarization Mode Dispersion Using Jones Eigenanalysis B. ![]()
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