Nonlinear phase noise in coherent optical OFDM transmission systems.

Corning Incorporated, SP-TD-01-1, Corning, NY 14831 USA.
Optics Express (Impact Factor: 3.55). 03/2010; 18(7):7347-60. DOI: 10.1364/OE.18.007347
Source: PubMed

ABSTRACT 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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    ABSTRACT: An improved zero-interpolation method with signal clipping to improve fiber nonlinearity tolerance in the long-haul coherent optical orthogonal frequency division multiplexing system (CO-OFDM) is presented. The new technique is implemented by interpolating zero subcarriers and selecting the odd subcarriers to carry data and clipping conventional CO-OFDM signal at zero. With such a scheme, the effect of fiber nonlinearity can be mitigated, and the wanted signal carried on odd subcarriers is orthogonal to clipping noise, which falls on even frequencies. Simulation shows that the system Q value is improved by more than 2 dB at the length of 960 km Key wordscoherent optical communication–fiber nonlinearity–signal clipping–orthogonal frequency division multiplexing (OFDM)
    Wuhan University Journal of Natural Sciences 01/2011; 16(1):38-42.

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