Nonlinear interference noise in 100-Gbit s-1communication lines with the DP-QPSK modulation format (original) (raw)
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IEEE Photonics Technology Letters, 2000
We experimentally investigate the probability density function (pdf) of sampled bits in common intensity-modulated direct-detection systems in linear and nonlinear regime, both single-channel and wavelength-division-multiplexed. To this aim, we use a recirculating fiber loop and selectively obtain the sample pdf for the various bits in a given sequence, which allows separating the intersymbol interference (ISI) effects. Our measurements confirm a recent theoretical simplified model, suggesting that, under the above conditions, a generalized analytic form is a good approximation of the true pdf, provided that a pattern-dependent effective noise density and noiseless signal value are assumed: all the pdfs estimated from the experimental data are indeed well fitted by this analytic form. Moreover, when nonlinear effects become dominating, the analytic form is still fitting properly the data histograms, showing, however, that the effective noise density increases. In the above regime, we clearly observe that ISI also affects the increase of the effective noise density.
International Journal of Information and Communication Technology Research, 2019
In this paper, we propose to use discretized version of the so-called Enhanced Gaussian Noise (EGN) model to estimate the non-linearity effects of fiber on the performance of optical coherent and uncompensated transmission (CUT) systems. By computing the power of non-linear interference noise and considering optical amplifier noise, we obtain the signal-to-noise (SNR) ratio and achievable rate of CUT. To allocate power of each CUT channel, we consider two optimization problems with the objectives of maximizing minimum SNR margin and achievable rate. We show that by using the discretized EGN model, the complexity of the introduced optimization problems is reduced compared with the existing optimization problems developed based on the so-called discretized Gaussian Noise (GN) model. In addition, the optimization based on the disctretized EGN model leads to a better SNR and achievable rate. We validate our analytical results with simulations and experimental results. We simulate a five-channel coherent system on OptiSystem software, where a close agreement is observed between optimizations and simulations. Furthermore, we measured SNR of commercial 100Gbps coherent transmitter over 300 km single-mode fiber (SMF) and non-zero dispersion shifted fiber (NZDSF), by considering single-channel and three-channel coherent systems. We observe there are performance gaps between experimental and analytical results, which is mainly due to other sources of noise such as transmitter imperfection noise, thermal noise, and shot noise, in experiments. By including these sources of noise in the analytical model, the gaps between analytical and experimental results are reduced. Optical Coherent Transmission Systems, Fiber Non-linear Interference Noise, Power Allocation, Minimum Signal-to-Noise-Ratio (SNR) Margin, Maximum Achievable Capacity.
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Physics Procedia, 2010
We analyzed the impact of nonlinear phase noise caused by Gorden-Mollenauer effect in single-channel return-tozero differential phase-shift-keying (RZ-DPSK) transmission in dependence of system bit rates, dispersion compensation schemes and different fiber types. The investigation is reported by simulating RZ-DPSK signals for 3200km, taking into account penalties in Q-factor induced by nonlinear phase noise. From these simulation results, higher bitrate systems, system with pre-compensation schemes and system using stand single mode fiber transmission are more robust against nonlinear phase noise. Furthermore, by looking into the standard deviation of the signal intensity and phase for all sampling points within one-bit duration, we observed that optical noise can be washed out from the bit center during propagation.
Intersymbol interference in DQPSK fibre-optic systems
European Transactions on Telecommunications, 2009
The limited bandwidth of high-speed transmitter and receiver hardware gives rise to intersymbol interference (ISI) in digital communication systems. The influence of such ISI is investigated in a low-complexity fibreoptical setting, using differential quaternary phase-shift keying (DQPSK) modulation. The ISI is approximated by a memoryless, stochastic model, for use in applications where neither equalisation nor sequence detection can be afforded. The channel capacity of this model is calculated and shown to depend strongly on the transmitter calibration. More than 3 dB is gained, at a target bit error rate (BER) of 10 −6 , by allowing the transmitted phase levels to deviate from their nominal multiples of π/2 by up to 7%.
Optimization of Q-Values for Coherent Optical Transmission Network
Rajshahi University Journal of Science and Engineering, 2015
In this paper we have analyzed the Gaussian Non-linear Interference (G<sub>NLI</sub>) spectrum considering non identical channels, non-identical links and Amplified Spontaneous Emission (ASE) noise power spectrum for Coherent Optical Transmission Network (COTN) to calculate the Optical Signal to Noise Ratio (OSNR) and Quality (Q) values. In this study, three different Baud rate values (13.875Gbaud, 27.75Gbaud, and 55.5Gbaud) are considered to compute the Q values and OSNR in the COTN. Consequently, the COTN produces 111 Gb/s, 222 Gb/s and 444 Gb/s line rates for three different Baud rate values (13.875Gbaud, 27.75Gbaud, and 55.5Gbaud) respectively in PM-16QAM modulation format. It is confirmed that the OSNR is always greater than Q values. It is also found that the differences between OSNR and Q are 0.23dB, 1.73dB, and 3.24dB for 111Gb/s, 222Gb/s and 444Gb/s line rates respectively. Here transmission of launch power per span, number of channels, number of spans and the f...
Improved Expression for Intensity Noise in Subcarrier Multiplexed Fiber Networks
The relative intensity noise (RIN) plays an important role in subcarrier multiplexed multimedia over fiber (MOF) networks. The RIN is conventionally considered to be proportional to the square of the mean optical power. This is true under small signal, single channel conditions. Nevertheless, experiments by us and many others have shown that the RIN also increases with the modulation index m that reflects the power of the stochastic modulating signal s(t). Accurate characterization of the RIN is important especially in MOF systems supporting sub carrier multiplexed radio signals in addition to digital data. Modern MOF links tend to have large carrier to sideband ratio that enhances RIN. In this paper, a mathematical expression for the RIN is derived from fundamental principles that shows the dependency of RIN on modulation index m and modulating multimedia signal power E[s 2 (t)]. The new expression better explains the excess increment of noise power in MOF systems. The signal to noise ratio is analyzed using the new expression and numerical evaluations are done considering DOCSIS specifications.
Nonlinear Phase Noise in Optical-Fiber-Communication Systems
Journal of Lightwave Technology, 2000
Gordon and Mollenauer, in their famous paper published in 1990, laid out how the interplay between the nonlinear Kerr effect in optical fibers and the amplified spontaneousemission (ASE) noise from the optical-amplifiers results in enhanced levels of noise and degrades the performance of modulation schemes that encode information in, particularly, the phase of the optical carrier. This phenomenon has been termed as nonlinear phase noise in the literature. In this paper, we first present a comparative and critical review of previous techniques that have been proposed for the analysis of nonlinear phase noise by forming a classification framework that reveals some key underlying features. We then present a unifying theory and a comprehensive methodology and computational techniques for the analysis and characterization of nonlinear phase noise and its impact on system performance by building on and extending previous work that we identify as most favorable and systematic. In our treatment, we consider a multichannel multispan optically amplified dense wavelength-division multiplexed system and develop general techniques for the analysis of the intricate interplay among Kerr nonlinearity, chromatic dispersion, and ASE noise, and for computing the bit-error-ratio performance of differential phase-shift-keying (DPSK) systems. By means of the extensive results we present, we demonstrate and argue that correlated noise behavior plays a most significant role in understanding nonlinear phase noise and its impact on DPSK system performance.