Inverse QR decomposition (IQRD) blind equalizer for QAM coherent optical systems

Abstract

Advanced digital signal processing techniques have a vital role in the development of emerging and next generation ultrahigh speed optical networks. These techniques highly contribute to the improvement of system spectral efficiency. Blind equalizers have recently been used to compensate for linear fiber impairments. In this paper we apply the inverse QR decomposition (IQRD), algorithm for blind equalization in 14Gbaud-16QAM coherent receiver. IQRD is widely used in wireless communications and known for its inherent stability in finite precision environment. We compare its performance with the standard Constant Modulus Algorithm (CMA) and Recursive Least Squares (RLS) algorithm in terms of convergence rate (CR) and bit error rate (BER). Our simulation results show that IQRD algorithm achieves similar CR and BER performance as those of standard RLS algorithm. However, in finite precision environment, which is more appropriate for practical implementation, and results in lower system power consumption (human friendly or Green solution), IQRD completely outperforms the RLS technique. A substantial reduction in BER of two orders of magnitude at 14 bit resolution is achieved for the optical system under consideration.