WDM Network Design

Frequency Chirp

When pulses are generated at the transmitted end, intensity modulation causes phase modulation due to the carrier-induced change in the refractive index. This change is inherently due to the laser linewidth. Such optical pulses with a time-dependent phase shift are called chirped pulses. The optical spectrum is broadened due to this chirp. Theoretically, the chirp-induced power penalty is difficult to calculate, but it can be approximated to a 0.5 dB margin in system design (Chirp is also defined in Chapter 2.)

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