Layered ACO-FOFDM for IM/DD Systems

doi:10.3969/j.issn.1673-5188.2017.03.008

ZTE Communications ›› 2017, Vol. 15 ›› Issue (3): 56-62.DOI: 10.3969/j.issn.1673-5188.2017.03.008

• Research Paper • Previous Articles

Layered ACO-FOFDM for IM/DD Systems

GUO Mengqi, ZHOU Ji, TANG Xizi, QIAO Yaojun

Beijing University of Posts and Telecommunications, Beijing 100876, China

Received:2016-12-25 Online:2017-08-25 Published:2019-12-24
About author:GUO Mengqi (guomengqi@bupt.edu.cn) received her B.S. degree from Beijing University of Posts and Telecommunications, China in 2015. Currently, she is a Ph.D. candidate in School of Information and Communication Engineering and State Key Laboratory of Information Photonics and Optical Communications, Beijing University of Posts and Telecommunications. Her research interests include signal processing for optical orthogonal frequency division multiplexing systems.|ZHOU Ji (zhouji@bupt.edu.cn) received his B.S. degree in communication engineering from Beijing University of Posts and Telecommunications, China in 2012. Currently, he is a Ph.D. candidate in School of Information and Communication Engineering and State Key Laboratory of Information Photonics and Optical Communications, Beijing University of Posts and Telecommunications. His research interests include signal processing for optical orthogonal frequency division multiplexing systems and coherent optical communications.|TANG Xizi (tangxizi@bupt.edu.cn) received his B.S. degree from Beijing Technology and Business University, China in 2012. Currently, he is a Ph.D. candidate in School of Information and Communication Engineering and State Key Laboratory of Information Photonics and Optical Communications, Beijing University of Posts and Telecommunications. His research interests include signal processing for passive optical networks.|QIAO Yaojun (qiao@bupt.edu.cn) received his B.S. degree from Hebei Normal University, China in 1994, M.S. degree from Jilin University, China in 1997, and Ph.D. degree from Beijing University of Posts and Telecommunications (BUPT), China in 2000. He was with Lucent and Fujitsu from 2000 to 2007. In 2007, he joined BUPT, where he is currently a professor. His research interests include optical fiber communication system and network.
Supported by:
This work was supported in part by National Natural Science Foundation of China under Grant(Nos. 61427813);This work was supported in part by National Natural Science Foundation of China under Grant(61331010);and in part by ZTE Industry-Academia-Research Cooperation Funds

Abstract

Abstract:

We propose a layered asymmetrically clipped optical fast orthogonal frequency division multiplexing (ACO-FOFDM) scheme for intensity-modulated and direct-detected (IM/DD) systems. Layered ACO-FOFDM can compensate the weakness of conventional ACO-FOFDM in low spectral efficiency. For FOFDM system, the utilization of discrete cosine transform (DCT) instead of fast Fourier transform (FFT) can reduce the computational complexity without any influence on bit error rate (BER) performance. At transmitter, the superposition of multiple layers is performed in frequency domain, and the iterative receiver is used to recover transmitted signals by subtracting the clipping noise of each layer. We compare the BER performance of the proposed layered ACO-FOFDM system and DC-offset FOFDM (DCO-FOFDM) system with optimal DC-bias at the same spectral efficiency. Simulation results show that in terms of optical bit energy to noise power ratio, the layered ACO-OFDM system has 1.23 dB, 2.77 dB, 3.67 dB and 0.78 dB improvement at the forward error correction (FEC) limit compared with DCO-FOFDM system when the spectral efficiencies are 1 bit/s/Hz, 2 bits/s/Hz, 3 bits/s/Hz and 4 bits/s/Hz. The layered ACO-FOFDM system with zero DC-bias is more suitable for adaptive system, so this system also has potential for application in IM/DD systems.

Key words: FOFDM, ACO-FOFDM, DCT, spectral efficiency, IM/DD

GUO Mengqi, ZHOU Ji, TANG Xizi, QIAO Yaojun. Layered ACO-FOFDM for IM/DD Systems[J]. ZTE Communications, 2017, 15(3): 56-62.

Figures/Tables 8

Figure 1. Block diagram of ACO-FOFDM transmitter and receiver.

Figure 2. Transmitter block diagram of layered ACO-FOFDM.

Figure 3. Two different types of receiver structures with soft decision or hard decision.

Figure 4. Spectral efficiency comparison between layered ACO-FOFDM system and conventional ACO-FOFDM system.

Table 1 Comparison of real multiplications and real additions between N-point FFT and N-point DCT

	Real multiplications	Real additions
FFT	$N lo g 2 N - 3 N + 4$	$3 N lo g 2 N - 3 N + 4$
DCT	$N 2 lo g 2 N$	$3 N 2 lo g 2 N - N + 1$

Table 1 Comparison of real multiplications and real additions between N-point FFT and N-point DCT

	Real multiplications	Real additions
FFT	$N lo g 2 N - 3 N + 4$	$3 N lo g 2 N - 3 N + 4$
DCT	$N 2 lo g 2 N$	$3 N 2 lo g 2 N - N + 1$

Figure 5. BER performance comparison between soft decision and hard decision in 4PAM layered ACO-FOFDM.

Figure 6. BER performance for 4PAM layered ACO-FOFDM system and 16QAM layered ACO-OFDM system.

Figure 7. BER performance comparison between layered ACO-FOFDM system and DCO-FOFDM system with the same spectral efficiency. The spectral efficiencies are set to 1 bit/s/Hz,2 bits/s/Hz, 3 bits/s/Hz and 4 bits/s/Hz. The optimal dc-biases of DCO-FOFDM system are 4.9 dB, 7.2 dB, 9.2 dB and 11 dB for BPSK,4PAM, 8PAM and 16PAM [18].

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Layered ACO-FOFDM for IM/DD Systems

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