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DD Transmission: Experimental Demonstration
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  • Xiong Wu ,
  • Abdullah S. Karar ,
  • Kangping Zhong ,
  • Zeynep Nilhan Gürkan ,
  • Alan Pak Tao Lau ,
  • Chao Lu
Xiong Wu
The Hong Kong Polytechnic University, The Hong Kong Polytechnic University

Corresponding Author:[email protected]

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Abdullah S. Karar
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Kangping Zhong
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Zeynep Nilhan Gürkan
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Alan Pak Tao Lau
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In this article, the first experimental demonstration of a non-iterative electronic dispersion compensation (EDC) solution implemented at the transmitter using a finite impulse response (FIR) filter optimized with the Gerchberg-Saxton (GS) algorithm, is presented, for intensity-modulation and direct-detection (IM/DD) systems. The performance of the GS-based FIR filter is compared to the performance of the standard iterative GS algorithm in the transmission of a 56-Gb/s on-off keying (OOK) signal over 80 km of single mode fiber (SMF) with a chirp-free single drive Mach-Zehnder modulator (MZM). The transmitter employed a T/2-spaced N-tap GS based FIR filter with an 8-bit finite-precision arithmetic, while the receiver employed a J-tap adaptive T-spaced or T/2-spaced feed-forward equalizer (FFE) for combating residual inter-symbol interference (ISI). Furthermore, the influence of the pulse shape and modulation format on the measured bit error ratio (BER) is experimentally investigated, while changing the number of FIR taps N, the number of post-FFE taps J and the number of post-FFE samples-per-symbol spsRx. The pulse shapes and modulation formats considered in this work are: raised-cosine (RC) non-return-to-zero (NRZ), rectangular NRZ and  rectangular return-to-zero (RZ). It is shown that within the range of target digital extinction ratio (DER) for which the original iterative GS algorithm offers benefit, both methods for calculating the optimum FIR taps, outlined in Part I of this work, produce similar BER performance as predicted theoretically. Furthermore, the measured BER, using rectangular RZ with a 641-tap  T/2-spaced static FIR filter at the transmitter and a 3-tap adaptive T-spaced post-FFE at the receiver, is below the 7% hard-decision (HD) forward error correction (FEC) limit of 3.8x10-3.
01 Mar 2023Published in Journal of Lightwave Technology volume 41 issue 5 on pages 1428-1435. 10.1109/JLT.2022.3223987