Abstract

Addressing the nonlinearity induced signal degradation is of critical importance for harvesting the transparent benefits of an analog radio over fiber (A-RoF) architecture, to support mobile fronthaul (MFH) with high spectral efficiency and reduced latency. Here, for linearizing the low-latency A-RoF MFH using digital-domain fast Fourier transform /inverse fast Fourier transform (FFT/IFFT) assisted channel aggregation/de-aggregation (CA/DA), we propose and experimentally demonstrate a compatible adaptive frequency-domain (FD) nonlinear equalization scheme. This scheme is characterized by a much lower computational complexity compared with the popular time-domain Volterra nonlinear equalizer while delivering a comparable performance. The proposed equalization scheme is implemented using the FD two-box cascaded Hammerstein structure. It enables simplified coefficients estimation, computationally efficient equalization, FFT/IFFT calculation reusing in channel DA, and shared legacy one-tap FD linear equalization in the OFDM system. Experimental validations of the proposed nonlinear equalization approach are carried out via typical electroabsorption modulator (EAM) and Mach-Zehnder modulator (MZM) based intensity modulation and direct detection (IMDD) A-RoF links. Cost-effective fiber-optic (with EAM) and optical up-conversion enabled V-band millimeter-wave (mm-wave) fiber-wireless (with MZM) transmissions are demonstrated. Experimental results show that the proposed scheme can effectively improve the performances of both EAM and MZM based 10-km fiber-optic A-RoF MFH links, in terms of the (>8 dB) reduction of adjacent channel leakage ratio, (>10 dB) improvement of error-vector magnitude (EVM) and (>5 dB) enhancement of input intermediate-frequency (IF) power range, which retains an acceptable (below 8 %) EVM performance for the 64-QAM modulation. The input IF signal aggregates 8 125-MHz 64-QAM OFDM channels. Furthermore, the proposed scheme enables the transmission of a 5-Gbit/s aggregated IF 64-QAM signal over a 10-km fiber link and 1.2-m 60-GHz wireless channel, wherein a >12 dB improved input power margin is observed.

Low-complexity frequency-domain nonlinear equalizer with absolute operation for underwater wireless optical communications

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Opt. Express 31(14) 23086-23094 (2023)

Coherent digital-analog radio-over-fiber (DA-RoF) system with a CPRI-equivalent data rate beyond 1 Tb/s for fronthaul

Yicheng Xu, Qunbi Zhuge, Yunyun Fan, Mengfan Fu, Yixiao Zhu, Xiaobo Zeng, Hexun Jiang, Lilin Yi, Weisheng Hu, and Xiang Liu
Opt. Express 30(16) 29409-29420 (2022)

Digital Mobile Fronthaul Based on Delta–Sigma Modulation for 32 LTE Carrier Aggregation and FBMC Signals

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J. Opt. Commun. Netw. 9(2) A233-A244 (2017)

Code reservation enabled PAPR reduction of digital CDM based channel aggregation for mobile fronthaul

Zhuqing Ni, Songnian Fu, Haibo Li, Zheng Yang, Chenhui Xie, Xiang Li, Lei Deng, Ming Tang, Jingchi Cheng, and Deming Liu
Opt. Express 26(17) 21585-21593 (2018)

Upstream and Downstream Analysis of an Optical Fronthaul System Based on DSP-Assisted Channel Aggregation

Pablo Torres-Ferrera, Stefano Straullu, Silvio Abrate, and Roberto Gaudino
J. Opt. Commun. Netw. 9(12) 1191-1201 (2017)