Optical Fiber Communications 4th Edition by Gerd Keiser

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The influence of polarization-mode dispersion can be neglected for data rates up to a few Gb/s for intensity-modulated direct-detection systems. However, for higher rates, PMD can cause intersymbol interference (ISI) in long- span links. The ISI power penalty in decibels for PMD is approximately 65
where T is a bit period (1/bit rate) and is the power-splitting ratio between principal polarization states. The maximum power penalty occurs when = . If typical values of the expected value of the differential group delay are 1 ps over a 100-km link and 10 ps over a 1000-km link, find the maximum PMD power penalty for data rates of 10 and 100 Gb/s over these two link distances.