Analysis of Phase Noise and Gaussian Noise in terms of Average BER for DP 16-QAM Optical Coherent Receiver Using Digital Filters (original) (raw)
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The proposed paper utilized the concept of Coherent detection. A field received by advances in Digital Signal Processing (DSP), has renewed interest in optical communication systems with spectrally efficient modulation formats. Starting with the point of view in comparison between the DP QPSK and DP 16-QAM analyses of Phase Noise in terms of Average Bit Error Rate (BER) and Optical Signal to Noise Ratio (OSNR) has been done. OSNR component is used in order to introduce noise in the dual polarization Optical coherent receiver system. The Noise is analyzed under the influence of different filters. Finally the best filter with best result have chosen in order to have minimum phase noise. To improve the performance of coherent receiver, a DSP algorithms like Constant Modulous Algorithm (CMA) and Blind phase search algorithm are used to compensate Propagation Mode Dispersion (PMD),Chromatic Dispersion (CD) and to achieve high data rate.
Impact of Phase Noise and Compensation Techniques in Coherent Optical Systems
Journal of Lightwave Technology, 2000
One of the most severe impairments that affect coherent optical systems employing high-order modulation formats is phase noise due to transmit and receive lasers. This is especially detrimental in uncompensated links, where an ideal compensator for channel distortions and laser phase noise should first eliminate receive phase noise, then equalize channel distortions, and only later compensate for transmit phase noise. Unfortunately, the simultaneous presence of transmit and receive phase noise makes very difficult to discriminate between them, even in the presence of a pilot tone. Moreover, the picture is different for optical systems using single-carrier or orthogonal frequency division multiplexing, where transmit and receive phase noise components may have a different impact. All these aspects are analyzed and discussed in this paper. A novel digital coherence enhancement (DCE) technique, able to significantly reduce the phase noise of transmit or receive lasers by using an interferometric device plus a very simple electronic processing, is also described. The performance of this technique and the statistical properties of the residual phase noise are analytically derived and verified by simulations, showing a high increase of the maximum bit-rate-distance product. The practical implementation of DCE is finally discussed and some alternative implementation schemes are presented.
Optics Express, 2010
The impact of phase to amplitude noise conversion for QPSK, 16-QAM, and 64-QAM coherent optical systems are investigated with electronically-compensated chromatic dispersion (CD). The electronic equalizer is shown to convert the phase noise from the local oscillator (LO) to amplitude noise, limiting the amount of CD that can ideally be compensated digitally. The simulation results demonstrate that the performance of coherent systems can significantly be degraded with digitally compensated CD and LO phase noise. The maximum tolerable LO linewidth is also investigated for the different modulation formats and found to become increasingly stringent for longer transmission distance and higher symbol rate.
IEEE Photonics Journal, 2014
We propose a novel method of in-band estimation of optical signal-to-noise ratio (OSNR) using a digital coherent receiver, where OSNR is determined from second-and fourth-order statistical moments of equalized signals in any modulation format. Our proposed method is especially important in recently-developed Nyquist wavelength-division multiplexed (WDM) systems and/or reconfigurable optical-add/drop-multiplexed (ROADM) networks, because in these systems and networks, we cannot apply the conventional OSNR estimation method based on optical-spectrum measurements of the in-band signal and the out-of-band noise. Effectiveness of the proposed method is validated with computer simulations of Nyquist-WDM systems and ROADM networks using 25-Gbaud quadrature phase-shift keying (QPSK) and 16 quadrature-amplitude modulation (16-QAM) formats.
Digital Signal Processing for Optical Coherent Communication Systems
In this thesis, digital signal processing (DSP) algorithms are studied to compensate for physical layer impairments in optical fiber coherent communication systems. The physical layer impairments investigated in this thesis include optical fiber chromatic dispersion, polarization demultiplexing, light sources frequency and phase offset and phase noise. The studied DSP algorithms are considered as key building blocks in digital coherent receivers for the next generation of optical communication systems such as 112-Gb/s dual polarization (DP) quadrature phase shift keying (QPSK) optical transmission links.
Optics Express, 2011
We present a novel investigation on the enhancement of phase noise in coherent optical transmission system due to electronic chromatic dispersion compensation. Two types of equalizers, including a time domain fiber dispersion finite impulse response (FD-FIR) filter and a frequency domain blind look-up (BLU) filter are applied to mitigate the chromatic dispersion in a 112-Gbit/s polarization division multiplexed quadrature phase shift keying (PDM-QPSK) transmission system. The bit-error-rate (BER) floor in phase estimation using an optimized one-tap normalized least-mean-square (NLMS) filter, and considering the equalization enhanced phase noise (EEPN) is evaluated analytically including the correlation effects. The numerical simulations are implemented and compared with the performance of differential QPSK demodulation system.
Compensation of Laser Frequency Fluctuations and Phase Noise in 16-QAM Coherent Receivers
IEEE Photonics Technology Letters, 2013
Frequency fluctuations caused by mechanical vibrations, power supply noise, and other mechanisms are detrimental to the phase estimator performance in high speed intradyne coherent optical receivers. In this letter, we propose the use of a low-latency parallel digital phase lock loop in combination with common feed-forward carrier phase recovery algorithms in order to compensate both the phase noise and laser frequency fluctuation effects on 16-quadrature amplitude modulation receivers. Numerical results demonstrate the excellent behavior of the proposed two-stage carrier recovery scheme.
Digital Coherent Receiver for Optical Transmission - Lazaro Hermoso
Digital Coherent Receiver for Optical Transmission - Lazaro Hermoso, 2009
Keywords: Coherent Detection, Local Oscillator, Sensitivity, Shot noise, Polarization Multiplexing. Abstract: The purpose of this project is to study the basis of optical coherent detection associated with digital signal processing and to design and implement such a receiver. The investigated coherent can be used to detect arbitrary complex modulation formats as it is capable of splitting polarization multiplexed signals and provides the real and imaginary parts of the optical field. After coherent detection, the signal is digitize to perform DSP in order to digitally obtain the clock from the signal received and compensate for the linear impairments that previously affected the signal. For that purpose the digital coherent receiver implemented is composed by three modules: the first module is a clock recovery that can obtain the clock signal from the received signal. A second module that, using Digital Signal Processing (DSP), is able to compensate Chromatic Dispersion (CD) and Polarization Mode Dispersion (PMD) using adaptive filters. These filters are programmed to use two kinds of adaptive algorithms: LMS and CMA, which can be previously selected. The third module is in charge of the phase noise estimation to compensate for the rotation that causes this impairment in the constellation sent. Two different architectures for phase noise estimation are compared. After designing the receiver in Matlab® we validate its functionality. For that we use the VPItransmissionMaker TM tool in which we can simulate a realistic optical communication system, and, introducing our designed receiver model into the communication system the receiver‟s capability to compensate CD, PMD and Phase Noise is studied. Furthermore, changing the optical communication system properties, we put the receiver ‟s robustness to test. We also change different configurations of the receiver and study how it influences the reception of the signal.
Optics Express, 2010
The bit-error rate (BER) expressions of 16-phase-shift keying (PSK) and 16-quadrature amplitude modulation (QAM) are analytically obtained in the presence of a phase error. By averaging over the statistics of the phase error, the performance penalty can be analytically examined as a function of the phase error variance. The phase error variances leading to a 1-dB signal-to-noise ratio per bit penalty at BER=10 −4 have been found to be 8.7 × 10 −2 rad 2 , 1.2 × 10 −2 rad 2 , 2.4 × 10 −3 rad 2 , 6.0 × 10 −4 rad 2 and 2.3 × 10 −3 rad 2 for binary, quadrature, 8-, and 16-PSK and 16QAM, respectively. With the knowledge of the allowable phase error variance, the corresponding laser linewidth tolerance can be predicted. We extend the phase error variance analysis of decision-aided maximum likelihood carrier phase estimation in M-ary PSK to 16QAM, and successfully predict the laser linewidth tolerance in different modulation formats, which agrees well with the Monte Carlo simulations. Finally, approximate BER expressions for different modulation formats are introduced to allow a quick estimation of the BER performance as a function of the phase error variance. Further, the BER approximations give a lower bound on the laser linewidth requirements in M-ary PSK and 16QAM. It is shown that as far as laser linewidth tolerance is concerned, 16QAM outperforms 16PSK which has the same spectral efficiency (SE), and has nearly the same performance as 8PSK which has lower SE. Thus, 16-QAM is a promising modulation format for high SE coherent optical communications.