Analytical results on channel capacity in uncompensated optical links with coherent detection (original) (raw)
Related papers
Journal of Lightwave Technology, 2015
We consider the transmission of Nyquistwavelength-division-multiplexed (NyWDM) channels based on polarization-multiplexed m-ary QAM multilevel modulation formats with DSP-based coherent detection over point-to-point uncompensated periodically amplified uniform fiber links. Taking into account both the effect of amplified spontaneous emission (ASE) noise accumulation and generation of non-linear interference (NLI) introduced by fiber propagation, we propose three different design strategies: the maximization of both the Q margin and the span-loss margin, for a given span length, and the maximization of the total link length given a target performance. We propose and apply an approximation for the Gaussian-Noise(GN) model in order to evaluate the NLI intensity, deriving for the three design strategies the merit of link and signal parameters. Finally, we validate the proposed methodologies using experimental and simulative results already published in literature.
Analysis of high capacity short reach optical links
2017
Over the last few years, the global Internet traffic has grown exponentially due to the advent of the social networks, high definition streaming, online gaming, high performance computing and cloud services. The network is saturating, facing a challenge to provide enough capacity to such ever-demanding bandwidth expensive applications. Fiber optic communications is the only technology capable of dealing such high demands due to its advantages over the traditional electrical transmission technology. The short haul transmissions currently rely on direct detection due to low cost, low power and low complexity as compared to the coherent detection schemes. In order to increase the bit rate, several advance modulation formats are under investigation for short reach transmissions. Such links mostly use intensity modulation direct detection (IMDD) schemes providing a simple system when compared with the coherent receivers. In this thesis the performance of Multilevel Pulse Amplitude Modula...
Optics Express, 2014
A number of critical issues for dual-polarization single-and multi-band optical orthogonal-frequency division multiplexing (DP-SB/MB-OFDM) signals are analyzed in dispersion compensation fiber (DCF)-free long-haul links. For the first time, different DP crosstalk removal techniques are compared, the maximum transmission-reach is investigated, and the impact of subcarrier number and high-level modulation formats are explored thoroughly. It is shown, for a bit-error-rate (BER) of 10 −3 , 2000 km of quaternary phase-shift keying (QPSK) DP-MB-OFDM transmission is feasible. At high launched optical powers (LOP), maximum-likelihood decoding can extend the LOP of 40 Gb/s QPSK DP-SB-OFDM at 2000 km by 1.5 dB compared to zero-forcing. For a 100 Gb/s DP-MB-OFDM system, a high number of subcarriers contribute to improved BER but at the cost of digital signal processing computational complexity, whilst by adapting the cyclic prefix length the BER can be improved for a low number of subcarriers. In addition, when 16-quadrature amplitude modulation (16QAM) is employed the digital-toanalogue/analogue-to-digital converter (DAC/ADC) bandwidth is relaxed with a degraded BER; while the 'circular' 8QAM is slightly superior to its 'rectangular' form. Finally, the transmission of wavelength-division multiplexing DP-MB-OFDM and single-carrier DP-QPSK is experimentally compared for up to 500 Gb/s showing great potential and similar performance at 1000 km DCF-free G.652 line.
Journal of Lightwave Technology, 2021
International standardization bodies (IEEE and ITU-T) working on the evolution of transmission technologies are still considering traditional direct detection solutions for the most relevant short reach optical link applications, that are Passive Optical Networks (PON) and intra-data center interconnects. Anyway, future jumps towards even higher bit rates per wavelength will require a complete paradigm shift, moving towards coherent technologies. In this paper, we thus study both analytically and experimentally the scaling laws of unamplified coherent transmission in the short-reach communications ecosystems. We believe that, given the extremely tight technoeconomic constraints, such a revolutionary transition towards coherent in short-reach first requires a very detailed study of its intrinsic capabilities in largely extending the limitation currently imposed by direct detection systems. To this end, this paper focuses on the ultimate physical layer limitations of unamplified coherent systems in terms of bit rate and power budget. The main parameters of our performance estimation model are extracted through fitting with a set of experimental characterizations and later used as the starting point of a scaling laws study regarding local oscillator power, modulator-induced attenuation, bit rate, and maximum achievable power budget. The analytically predicted performance is then verified through transmission experiments, including a demonstration on a 37-km installed metropolitan dark fiber in the city of Turin. Our findings show that coherent detection without optical pre-amplification and using PM-QPSK can tolerate optical power budget (OPB) well above, for instance, the 29 dB imposed by the current PON standards even at extremely high raw bit rates up to 800 Gbps. PM-16QAM, on the other hand, can provide up to 190 Gbps at 29 dB OPB only if combined with soft FEC algorithms. Even higher bit rate are also shown for the less demanding power budget needed in intra-data centers links.
Bell Labs Technical Journal, 2010
100 Gb/s end-to-end broadband optical solutions are attractive to cope with the increasing demand for capacity. Polarization-division-multiplexed (PDM) quaternary-phase-shift-keying (QPSK) paired with coherent detection has been found to be promising for upgrading optical legacy systems based on 50 GHz wavelength slots thanks to its high spectral efficiency (2 bit/s/Hz) and its tolerance to linear effects. One of the major concerns for the deployment of such a solution is the transmission reach, mainly limited by nonlinear effects. This limitation can be exacerbated over non-zero dispersion shifted fiber (NZDSF) due to low local chromatic dispersion of the transmission fiber. The aim of this paper is first to report on the benefits brought by combining coherent detection techniques with advanced modulation formats as compared to conventional direct detection schemes for optical fiber communications. Digital signal processing paired with coherent detection is described to point out the efficiency of a coherent receiver to combat noise and to mitigate linear impairments. We then report on nonlinear tolerance of 100 Gb/s coherent PDM-QPSK through an 8 Tb/s transmission over a dispersionmanaged link based on low dispersion fibers. © 2010 Alcatel-Lucent.
Journal of Lightwave Technology, 2000
We report on an experimental long-haul transmission of a 28 Gbaud PS-QPSK signal in WDM scenarios. This report presents, to the authors' knowledge, a novel implementation of an optical coherent receiver for the polarization-switched quadrature phase shift keying (PS-QPSK) modulation format, with minor variations on the standard coherent PDM-QPSK receiver. We compare the performance of PS-QPSK with that of PDM-QPSK, over a WDM system based on 100 Gb/s PDM-QPSK and standard single mode fiber (SSMF), and we demonstrate its interest for software-defined optical transceivers operating over dispersion managed and non-managed transmission links.
New bounds on the capacity of fiber-optics communications
By taking advantage of the temporal correlations of the nonlinear phase noise in WDM systems we show that the capacity of a nonlinear fiber link is notably higher than what is currently assumed. This advantage is translated into the doubling of the link distance for a fixed transmission rate.
Analytical Modeling of Nonlinear Propagation in Uncompensated Optical Transmission Links
IEEE Photonics Technology Letters, 2011
We present analytical results on the impact of nonlinear propagation in uncompensated links. We test the accuracy of our model in the context of ultradense wavelength-division-multiplexing polarization-multiplexed quadrature phase-shift keying (PM-QPSK) systems, at the Nyquist spectral efficiency limit. We show that the predicted system performance matches simulation results very accurately over a broad range of system scenarios. A simple closed-form analytical formula provides an effective tool for the quick and accurate prediction of system performance. Index Terms-Dense wavelength-division multiplexing (DWDM), Nyquist wavelength-division multiplexing (WDM), optical transmission, polarization-multiplexed quadrature amplitude modulation (PM-QAM), polarization-multiplexed quadrature phase-shift keying (PM-QPSK), uncompensated systems.
Journal of Microwaves, Optoelectronics and Electromagnetic Applications
The demand for higher speed at a lesser transmission cost per bit resulted in growth of optical networks with improved spectral efficiency even at narrower channel spacing. Incorporation of multilevel modulation formats in DWDM system led to the exploration of the 25 GHz channel grid, popularly known as Ultra Dense Wavelength Division Multiplexed (UDWDM) systems, opening new research frontiers. At such channel spacing's, nonlinear optical effects impose severe system impairments and hence robust modulation schemes are currently being investigated. This paper presents a simulative model to implement and analyze alternative polarized DQPSK modulated UDWDM system to evaluate its resilience to XPM and fiber nonlinearity. An UDWDM system supporting 32 channels, each operating at 40 Gbps and spaced at 25 GHz is studied numerically for long-haul optical communication system using OptiSystem simulator to estimate OSNR penalties to mitigate XPM effects. The major detrimental factors encountered in link design have been estimated to evaluate the system performance in terms of Q value for different number of channels and with varied input power. The analysis reports acceptable performance for DQPSK format up to a link distance of 1500 Km and also claims a better tolerance to dispersion and nonlinearities at higher input power levels.