An adaptive algorithm for reducing phase error in digital carrier recovery for high-order QAM signals

Abstract

This paper describes an adaptive software aided technique for phase error reduction in digital carrier recovery (CR) for high-order Quadrature Amplitude Modulation (QAM). Simulations and analytical results illustrate a phase error variance improvement of at least 30 dB compared to conventional CR, leading to more than 3 dB processing gain enhancement for high-order QAM, using the simple 4 th power phase estimation technique. The new technique can be employed to improve the performance of any CR loop, at the cost of slight complexity overhead independent of the modulation order.

Low-Complexity Blind Carrier Phase Recovery for C-mQAM Coherent Systems

“…An important limit in these coherent optical communication systems is the phase noise induced by the laser at transmitter and the free running local oscillator (LO) laser at receiver, which constrains the laser linewidth tolerance and a cost-effective implementation [5]- [10]. Moreover, the higher order modulation signal is more sensitive to phase noise, where the system performance suffers seriously from phase noise at larger laser linewidths [8]- [10]. As a result, the development of coherent optical systems is highly dependent on efficient techniques for the laser phase noise.…”