On the performance of all-optical OFDM based PM-QPSK and PM-16QAM
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On the performance of all-optical OFDM based PM-QPSK and PM-16QAM Julian Hoxha1
· Satoshi Shimizu2 · Gabriella Cincotti3
© Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract A polarization multiplexed all-optical orthogonal frequency division multiplexing (AO-OFDM) system is investigated analytically and numerically, with 12.5 Gbaud symbol rate, that is compatible with the International Telecommunication Union flexible grid. We demonstrate that fast adaptive filtering is not require at the receiver and chromatic dispersion with polarization mode dispersion can be compensated without the cyclic prefix insertion, with the maximum spectral efficiency by using proper optical filter. System performance are numerically and analytically evaluated considering nonlinear effects and power consumption, evidencing a good agreement between the theoretical model and numerical results. We compare AO-OFDM performance with coherent OFDM scheme using the derived theoretical formula and numerical results. 21 subcarriers are investigated with quadrature phase shift keying modulation and 7 subcarriers in case of 16-quadrature amplitude modulation, with a total capacity of 976.5 Gb/s and 651 Gb/s, respectively, considering 7% forward error correction overhead. Keywords Fiber optics · Optical communications systems · All optical OFDM · Complex modulation · Phase noise · Non linear effects
1 Introduction Orthogonal frequency division multiplexing (OFDM) and Nyquist-wavelength division multiplexing (N-WDM) are closely spaced multi-carrier approaches that maximize spectral efficiency and reduce the cost per bit in future optical networks [1]. Both technologies provide a high-degree of flexibility at the spectrum level utilizing variable number of low data-rate, partially overlapped subcarriers, to suitably adjust the aggregate rate [2–15]. Subcarrier filtering and multiplexing are performed either in electrical or optical domain. In electrical domain high-speed digital to analog converters (DAC) and optical modulators are required, whereas suitable
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Julian Hoxha [email protected] Gabriella Cincotti [email protected]
1
Computer Engineering Department, Epoka University, Tirana, Albania
2
National Institute of Information and Communications Technology (NICT), Tokyo, Japan
3
Engineering Department, University Roma Tre, via Vito Volterra 62, 00146 Rome, Italy
optical filters with sinc or rectangular shapes are used for alloptical OFDM (AO-OFDM) and optical N-WDM [16,17]. N-WDM presents lower bandwidth and sampling requirements (minimum of 2 samples per symbol) at the receiver (RX) side, compared to OFDM (4 samples per symbol) [18]. AO-OFDM technology on the other hand is still under intensive research investigation thanks to power consumption reduction. Chromatic dispersion (CD) and polarization mode dispersion (PMD) can be effectively estimated and compensated using coherent detection schemes and digital signal processors (DSP), at a relative low cost [18–20]. The basic principle of AO-OFDM
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