From Lightwave Technology

9.6.3 PMD and Polarization-Dependent Losses

As discussed in Section 3.4, fluctuations in the residual birefringence of optical fibers change the state of polarization (SOP) of all channels in a random fashion and also distort optical pulses because of random changes in the speeds of the orthogonally polarized components of the same pulse (PMD). In a realistic WDM system, one should also consider the effects of polarization-dependent loss (PDL) associated with various optical components (see Section 3.5). Moreover, when optical amplifiers are used periodically for loss compensation, the polarization-dependent gain (PDG) of such amplifiers can also degrade a WDM system. For this reason, considerable attention has been paid to understanding the impact of PMD, PDL, and PDG on the performance of WDM systems [157]-[163].

The main problem from the standpoint of system performance is that fiber birefringence can change with time in a random fashion owing to variations in temperature and stress along the fiber link. As a result, both PMD and PDL can lead to channel outage – a phenomenon in which the BER of a channel increases so much that it is effectively out of use. Such an outage can occur at random times for random durations. The only...

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Topics of Interest

9.6.4 Wavelength Stability and Other Issues The design of modern WDM systems requires a careful consideration of many transmitter and receiver characteristics. An important issue concerns the...

2.13.7   Polarization-Mode Dispersion Compensation Fibers are specified by an average differential group delay (DGD) in ps or a mean DGD coefficient in . For a low-PMD fiber, the mean DGD...

9.4.1 Amplitude Fluctuations Consider the source of amplitude fluctuations first. As discussed in Section 4.2, XPM originates from the nonlinear nature of the refractive index, which produces a phase...

2.9.4   Polarization-Dependent Loss When light travels through matter it suffers power loss. One of the contributors to power loss is polarization. Virtually all optically transparent materials...

4.4.4 Optical Gain Equalizers In DWDM transmission, optical gain equalization is required because the DWDM signals eventually become unequal in power. This is because the gain characteristic of...

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