Impact of ADC Sampling Speed and Resolution on Uncompensated Long-Haul 111-Gb/s WDM PM-QPSK Systems

We analyzed the effect of analog-to-digital conversion on the performance of polarization-multiplexed quadrature phase-shift keying at 111 Gb/s. We address analog-to-digital converter sampling speed, resolution, and clipping, taking into account both linear and nonlinear propagation effects over a 20-span uncompensated wavelength-division-multiplexing long-haul test-link with 50-GHz channel spacing, using either standard single-mode fiber or nonzero dispersion-shifted fiber. We assumed realistic optical and electrical filters. We found that penalty can be limited within 0.5 and 0.8 dB, if at least 5 bits of resolution and 1.6 or 1.5 samples per symbol are used, respectively.