Optical domain scheme of pilot-tone-aided carrier phase recovery for Nyquist single-carrier optical communication system

Abstract

We propose an optical domain pilot-aided carrier phase recovery (PA-CPR) scheme used in a single-carrier Nyquist system. A comprehensive mathematical description of the proposed PA-CPR scheme is presented. Optimal parameters for the system are obtained through optimizations. Furthermore, we propose the two-stage PA-CPR algorithm combinations which use the maximum likelihood or constellation transformation phase estimation as the second stage just after the pilot phase compensation. We also make the evaluation and comparison of the linewidth tolerance performances among the proposed two-stage PA-CPR algorithm combinations and other typical CPR algorithms in a 28-Gbaud Nyquist polarization-division multiplexed (PDM)-16QAM optical communication system. The calculation results show that the proposed twostage PA-CPR algorithm combinations, which have lower complexities, show better performances than others.

A Chromatic Dispersion-Tolerant Frequency Offset Estimation Algorithm Based on Pilot Tone for Digital Subcarrier Multiplexing Systems

“…Moreover, the pilot tone is adopted to estimate the carrier phase noise. The pilot tone-based AEPD and carrier phase estimation (CPE) could reduce computational complexity compared with blind ones [17][18][19][20]. The principle of those pilot tone-based algorithms will be introduced in our following papers.…”

“…In the case of a relatively large laser linewidth symbol duration product line s f T Δ  , where line f Δ denotes laser linewidth and s T represents subcarrier symbol duration, a secondstage CPE is introduced to compensate for the residual phase noise. In this paper, the residual phase noise is compensated by the maximum likelihood (ML) algorithm because, with the majority of the phase noise canceled by the first-stage CPE, ML could improve linewidth tolerance with low complexity cost [17,18]. With the DSP scheme already introduced above, the principle of the two-stage FOE scheme will be described in detail.…”

“…The PSR should be large enough to make sure that the noise does not severely mask the pilot tone. At the same time, it should also be small enough to ensure sufficient power is allocated to the payload signal to maintain the optical signal noise ratio (OSNR) of the payload signal [17][18][19]. The optimization of PSR shall be discussed in Sections 4 and 5.…”

Pilot-added carrier-phase recovery scheme for Nyquist M-ary quadrature amplitude modulation optical fiber communication system

“…Carrier-phase recovery (CPR) is a significant and integral part of the digital signal processing (DSP) procedure to compensate for the phase noise (PN) induced by both the transmitter and the local oscillator (LO) lasers. Many blind CPR algorithms have been proposed and demonstrated to mitigate the PN [1][2][3][4][5][6][7][8][9][10] . Among these methods, blind phase search (BPS) has the best linewidth tolerance for arbitrary M-QAM formats, but at the cost of high computation complexity [1] .…”

“…In this work, a two-stage CPR scheme is proposed, in which the optical pilot-aided (PA) algorithm [7] works as the first stage and a so-called crossed constellation transformation (CCT) algorithm works as the second algorithm. Using the optical pilots just alongside the Nyquist-WDM signal bands, we can mitigate or compensate for impairments such as frequency offset, carrier PN, etc.…”