EEPN and CD study for coherent optical nPSK and nQAM systems with RF pilot based phase noise compensation

Abstract

A radio frequency (RF) carrier can be used to mitigate the phase noise impact in n-level PSK and QAM systems. The systems performance is influenced by the use of an RF pilot carrier to accomplish phase noise compensation through complex multiplication in combination with discrete filters to compensate for the chromatic dispersion (CD). We perform a detailed study comparing two filters for the CD compensation namely the fixed frequency domain equalizer (FDE) filter and the adaptive least-mean-square (LMS) filter. The study provides important novel physical insight into the equalization enhanced phase noise (EEPN) influence on the system bit-error-rate (BER) versus optical signal-to-noise-ratio (OSNR) performance. Important results of the analysis are that the FDE filter position relative to the RF carrier phase noise compensation module provides a possibility for choosing whether the EEPN from the Tx or the LO laser influences the system quality. The LMS filter works very inefficiently when placed prior to the RF phase noise compensation stage of the Rx whereas it works much more efficiently and gives almost the same performance as the FDE filter when placed after the RF phase noise compensation stage.

Analytical BER performance in differential n-PSK coherent transmission system influenced by equalization enhanced phase noise

“…[ [26][27][28][33][34][35][36]. Among these methods, the digital coherence enhancement shows the best performance [26,36], while it requires a complicated hardware implementation to measure the LO laser phase fluctuation.…”

“…I. Fatadin et al have also studied the influence of the EEPN in quadrature phase shift keying (QPSK), 16-level quadrature amplitude modulation (16-QAM) and 64-QAM coherent transmission systems [24]. Meanwhile, the influence of EEPN on different CPE algorithms has also been investigated in detail by using numerical simulations [25][26][27][28][29]. Due to the EEPN, the requirement of laser 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 linewidth can not be generally relaxed for the transmission system with a higher symbol rate.…”

Digital Adaptive Carrier Phase Estimation in Multi-level Phase Shift Keying Coherent Optical Communication Systems

“…Meanwhile, due to the interplay between the electronic dispersion equalization (EDC) and the laser phase noise, an effect of equalization enhanced phase noise (EEPN) has been generated and will seriously degrade the performance of long-haul optical fiber communication systems [37][38][39][40][41][42]. Some investigations regarding the equalization enhanced phase noise have been carried out in the single-channel, the wavelength division multiplexing (WDM), the orthogonal frequency division multiplexing (OFDM), the dispersion predistorted, and the multi-mode optical transmission systems [43][44][45][46][47][48].…”

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

“…[19][20][21][22][23][24][25] In the transmission channels, the pilot tone experiences the same impairments as the data signal, thus it can jointly compensate for the laser PN, frequency offset (FO), and fiber nonlinearity. [19][20][21][22][23][24][25] In the transmission channels, the pilot tone experiences the same impairments as the data signal, thus it can jointly compensate for the laser PN, frequency offset (FO), and fiber nonlinearity.…”