Several optical modulation and detection schemes are compared by computing their spectral efficiencies over additive white Gaussian noise channels. The bandwidth savings of differential quadrature phase-shift keying (D-QPSK) over both direct-detection on-off keying and differential binary phase-shift keying suggest that D-QPSK can improve the reach and efficiency of wavelength-division multiplexing systems. To test the theory, Reed-Solomon and low-density parity-check forward error correction codes are designed and evaluated. The codes generally behave as expected, except that for D-QPSK the gains are hampered by the differential detector. It is further shown that neither multiple-symbol differential detection nor decision-feedback detection is attractive when using strong codes.
© 2003 IEEE
Gerhard Kramer, Alexei Ashikhmin, Adriaan J. van Wijngaarden, and Xing Wei, "Spectral Efficiency of Coded Phase-Shift Keying for Fiber-Optic Communication," J. Lightwave Technol. 21, 2438- (2003)