Nonlinear phase noise in coherent optical OFDM transmission systems

Corning Incorporated, SP-TD-01-1, Corning, NY 14831 USA.
Optics Express (Impact Factor: 3.49). 03/2010; 18(7):7347-60. DOI: 10.1364/OE.18.007347
Source: PubMed


We derive an analytical formula to estimate the variance of nonlinear phase noise caused by the interaction of amplified spontaneous emission (ASE) noise with fiber nonlinearity such as self-phase modulation (SPM), cross-phase modulation (XPM), and four-wave mixing (FWM) in coherent orthogonal frequency division multiplexing (OFDM) systems. The analytical results agree very well with numerical simulations, enabling the study of the nonlinear penalties in long-haul coherent OFDM systems without extensive numerical simulation. Our results show that the nonlinear phase noise induced by FWM is significantly larger than that induced by SPM and XPM, which is in contrast to traditional WDM systems where ASE-FWM interaction is negligible in quasi-linear systems. We also found that fiber chromatic dispersion can reduce the nonlinear phase noise. The variance of the total phase noise increases linearly with the bit rate, and does not depend significantly on the number of subcarriers for systems with moderate fiber chromatic dispersion.

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    • "A comparison with traditional QAM OFDM systems is analytically presented to explore the efficiency of proposed phase noise mitigation. Generally , the nonlinear phase noise is caused by fiber Kerr nonlinearity such as SPM, XPM, and FWM [5]. Moreover, the amplified spontaneous emission (ASE) due to optical amplifiers adds a random nonlinear phase noise that mainly affects the SPM, XPM, and FWM phenomena [7]. "
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    ABSTRACT: A new approach to mitigate the phase noise in all-optical OFDM systems is analytically modeled and numerically demonstrated. The interaction time between subcarriers is minimized by shaping the envelopes of QAM subcarriers and making a delay time between even and odd subcarriers. Return-to-zero (RZ) coding is adopted for shaping the envelopes of subcarriers. In addition, the subcarriers are alternately delayed (AD) by optical time delayers. The performance of an all-optical OFDM system, that implements the proposed technique, is analyzed and simulated. This system has 29 subcarriers with symbol rate of 25 Gsymbol/s and is composed of coupler-based inverse fast Fourier transform (IFFT)/fast Fourier transform (FFT) schemes. Each subcarrier is modulated with QAM format before shaping with RZ coding. Due to RZ being more affected by dispersion; a full periodic dispersion map is adopted to keep the total accumulated dispersion low. The results reveal that the nonlinear phase noise (NPN) due to fiber nonlinearity is significantly mitigated when the time delay between the odd and even subcarriers is equal to half the symbol period. The total phase noise variance is reduced from 9.3×10-3 to 6.1×10-3 rad2 when employing AD RZ-QAM for a transmission distance of 550 km. Furthermore, both the transmission distance and optical signal to noise ratio (OSNR) are improved when compared to all-optical OFDM systems that adopt traditional QAM modulation formats.
    Full-text · Article · Oct 2015 · Optics Communications
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    • "In particular, Four-Wave Mixing (FWM) degrades the performance during fibre transmission as a result of the closely spaced optical channels [6] [7]. The nonlinear distortions become apparent when the launch power of the OFDM signal is above a system dependent threshold into the fibre [8]. The nonlinearities introduced into the signal propagation build up significantly over increasing transmission lengths [9]. "
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    ABSTRACT: A 25 Gb/s orthogonal frequency division multiplexing (OFDM) 60 GHz radio over fibre transmission system employing an externally injected gain switched DFB laser for millimetre wave generation is demonstrated. The effects of nonlinear distortions, due to a high launch power, on system performance are experimentally investigated. Single sideband (SSB) OFDM is employed to reduce the fibre nonlinearity effects. Keywords—radio over fibre (RoF), gain-switching, optical comb source, orthogonal frequency division
    Full-text · Conference Paper · Oct 2014
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    • "The phase noise contributions in CO-OFDM transmission are the following [4]: (I) Nonlinear optical fiber transmission produces a nonlinear phase noise. This nonlinear phase noise comes from the interaction of amplified spontaneous emission (ASE) with self-phase modulation (SPM), cross-phase modulation (XPM) and four-wave mixing (FWM) [9] "
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    ABSTRACT: In coherent optical orthogonal frequency division multiplexing (CO-OFDM) systems, phase noise has an important impact on the system performance. They are highly sensitive to phase noise induced by transmitter laser and local oscillator laser. We explain different kinds of phase noise effects on the OFDM signals and analyze the phase noise effect induced by transmitter laser and local oscillator. We analyze the standard RF-pilot (RFP) phase noise compensation method and explain its drawbacks. We provide two extended RFP schemes that overcome the drawbacks of the standard RFP scheme and enhance the performance of CO-OFDM systems. Furthermore, the phase noise effects for various laser linewidths and the effect of the received optical power (ROP) on the system performance are quantified. A CO-OFDM transmission system with 16-QAM is simulated with VPItransmissionMaker™ V8.5.
    Full-text · Conference Paper · Jan 2012
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