Can 100-Gb/s QPSK Signal Locate Adjacent to Legacy 10-Gb/s OOK Signal without Guard-Band?

TL;DR

This paper investigates the feasibility of locating 100-Gb/s QPSK signals adjacent to legacy 10-Gb/s OOK signals without guard bands, focusing on filter optimization to minimize phase error.

Contribution

It demonstrates that an optimized Wiener filter can effectively reduce phase error and SNR penalty in WDM systems with mixed modulation formats.

Findings

Wiener filter optimization minimizes phase error.

SNR penalty is 0.66 dB for single-mode fiber.

SNR penalty is 0.30 dB for nonzero dispersion-shifted fiber.

Abstract

For 100-Gb/s quadriphase-shift keying (QPSK) signal with on-off keying (OOK) signal in neighboring wavelength-division-multiplexed (WDM) channel, the smoothing filter in the feedforward phase estimation scheme must be optimized to minimize the phase error. With optimal Wiener filter, typical 0-dBm launched power 10-Gb/s OOK signals give a SNR penalty of 0.66 and 0.30 dB for standard single-mode and nonzero dispersion-shifted fibers, respectively.