Polarization
Polarization
is a property of light often exploited to positive effect for data
transmission. But light polarization can also manifest
as a cause of transmission limitations.
Polarization Mode Dispersion (PMD) is an important linear distortion that affects the performance of optical systems. PMD is a consequence of certain physical properties of optical fiber that result in distortion of optical pulses. These distortions result in dispersion of the optical pulse over time, as well as a reduction in peak power. While the outcome of PMD-induced distortion is similar to Chromatic Dispersion, it is not accumulated linearly, but stochastically. This means that its value cannot be predicted from one instant to the next, but its distribution (occurrence within a predictable range) can be.
Complicating factors that contribute to this unpredictability are as diverse as temperature change on optical fiber, wind load and wind turbulence on aerial optical fiber, and ice loading changing stresses on aerial optical fiber. One additional and significant constraint associated with characterizing and measuring PMD on optical fiber is the date of manufacture. In fact, optical fiber manufactured before approximately 1994 may not have been designed with PMD mitigation in mind.
Polarization Analysis Software
Luna Technologies' Polarization Analysis
Software can be used to display the response of an optical component
to a simulated input polarization state. This software,
combined with Luna's Optical Vector Analyzer, eliminates the tedious
and difficult task of polarization alignment often required for
measurement of today's advanced optical components. The
software plots insertion loss, group delay, and impulse response of
an optical component to a user-defined input polarization state.
Luna Polarization Analysis Software
Measuring Polarization Mode Distortion (PMD) in Optical Links
The capabilities of fiber optic communication networks depend greatly on the performance of optical fibers and cables. While chromatic and intermodal dispersion can be corrected and fairly well controlled, it is difficult to compensate for a stochastic phenomenon such as PMD. In spite of these difficulties, it is essential to characterize PMD in optical transport systems since it will adversely affect transmission rates. As data rates climb to 40GBit/sec and beyond, PMD characterization of transport systems will be all the more critical.
EXFO Distributed PMD Analyzers
Efficient & Reproducible PMD Tolerance Testing
New Ridge Technologies PMD sources and emulators enable assessment of performance degradation due to second-order PMD (SOPMD) and the interactions of noise, non-linearities, channel spacing, and chromatic dispersion with PMD. Optoelectronic transmitters, receivers, and compensators/equalizers can be characterized for PMD-related outages in minutes per year.
PMD Sources and Emulators