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In fiber optics, why would RZ-DPSK be more suited for long-haul transmissions over NRZ-DPSK? Is the tolerance to non-linearity due to the power intensity or something else?

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up vote 2 down vote accepted

RZ-DPSK is derived from NRZ-DPSK via a pulse carver, so you can see that a carrier will be more available than from the constant envelope of the NRZ. In NRZ the carrier arises from the phase shift chirps and non-linearities in that process.

Looking at the spectrum of the RZ vs. NRZ you will see a higher carrier to sideband ratio and a flatter power spectrum. All good things for recovering the signal on the other end.

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At higher bit rates and long haul links RZ is more prone to dispersion as compared to NRZ.

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It might be worth adding a bit more context to make this a more useful answer. – PeterJ Aug 23 '14 at 9:56

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