Fast tracking of polarization impairments using DSP algorithms in fiber for a coherent optical communication system

Abstract

In a 100G coherent optical fiber communication system, the equalization algorithm of polarization effects in fibers is generally integrated in digital signal processing (DSP) using a multiple input/multiple output (MIMO) equalizer to overcome the impairment due to the polarization effects in fiber. However, it was found in some extreme scenarios, such as the lightning strikes near the fiber cables, the Kerr effect and Faraday effect would induce very fast time‐varying state‐of‐polarization (SOP) and transient variation of principal‐state‐of‐polarization (PSP) of polarization mode dispersion (PMD) which would result in the coherent receivers unlocking. Faced with the difficulty, we propose a 3‐parameter RSOP model and design a window‐split structured Kalman filter equalization scheme instead of conventional MIMO equalizer to cope with this extreme scenario of large PMD combined with ultra‐fast rotation of SOP in presence of residual chromatic dispersion (RCD). The proposed equalization method has an excellent performance and can cope with RCD in the range of ±820 ps/nm under RSOP from 100 krad/s to 3 Mrad/s and DGD = 200 ps.

Low power digital signal processing-lite scheme for short-reach polarization demultiplexing-64 quadrature amplitude modulation coherent optical system

“…Accordingly, analysis based on knowledge of different algorithms, we evaluate the complexity of the proposed algorithm and make comparisons with conventional DSP. The comparison results show that for the complexity of CMA, 19 , 20 per output symbol requires 8N+2 (N is the filter taps number, N=3 or 11 with or without bandwidth unlimited) times complex multiplications, 4N times real additions, and 4N times complex additions, and for MCMA complexity, per output symbol requires 8N+4 times complex multiplications, 4N+2 times real additions, and 4N times complex additions based on the selection of k taps and Eq. (2)–(6).…”

Impacts of the measurement equation modification of the adaptive Kalman filter on joint polarization and laser phase noise tracking

“…For stability and real implementation, we introduce the noise covariance matching method into MKF, since it has lower complexity and is more practical to implement than other adaptive algorithms [20,21] . The adaptive estimations of covariance matrices of process and measurement noise Q k and R k are expressed in a compact form as Eqs.…”

Cavity dynamics of a hybrid mode‐locked figure of eight fiber laser

“…To capture the electrons' dynamics around the nucleus, in lattice structures, from one atom to another, and miscellaneous ultra‐short pulse industrial and scientific requirements; in‐depth exploration of mode‐locking phenomenon in various types of laser systems is required 1 . The usages comprise transforming and recasting materials, 2 optical sensing, 3 optical communications, 4 medical diagnostics, 5 and micromachining 6 . In a mode‐locked laser, every mode functions with a constant phase difference between itself and the others.…”