Abstract

In this paper, we proposed an improved mobile fronthaul architecture employing the SNR-improved delta-sigma digitization scheme and 4-level pulse amplitude modulation (PAM-4) format. Different from traditional 2-bit quantization, this scheme deploys two-fold delta-sigma quantization, which uses 1-bit delta-sigma modulator to quantize the signal, and another 1-bit delta-sigma modulator to quantize the in-band noise. A significant reduction of the in-band noise can be achieved only applying a differentiator, bringing about a much better noise shaping performance. Meanwhile, the two 1-bit streams can be combined and transmitted in a PAM-4 manner through an intensity modulation direct detection (IM-DD) channel. We have successfully experimentally demonstrated the digitization and transmission of 65536 quadrature amplitude modulation (QAM) baseband orthogonal frequency division multiplexing (OFDM) signal with sampling rate of 1.25 GSa/s over 20-km fiber with standard 10-Gbaud PAM-4 signal, with a signal to noise ratio (SNR) of 57.7 dB. Compared to the conventional 2-bit quantized OFDM scheme, experimental results show that a significant SNR improvement of 17.7 dB has been achieved by the proposed scheme. In addition, we also realized a transmission of 16384-QAM intermediate frequency (IF) signal at the center frequency of 3.5 GHz (with an SNR of 49.6 dB). An improvement of 15.9 dB can also be maintained.

Improving performance of mobile fronthaul architecture employing high order delta-sigma modulator with PAM-4 format

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Opt. Express 25(1) 1-9 (2017)

Hybrid fiber–THz fronthaul supporting up to 16384-QAM-OFDM with the delta-sigma modulation

Lu Zhang, Zefeng Chen, Hongqi Zhang, Zuomin Yang, Yixin Wu, Xiongbin Yu, Xiaodan Pang, Vjaceslavs Bobrovs, Oskars Ozolins, and Xianbin Yu
Opt. Lett. 47(17) 4307-4310 (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)

Probabilistic shaping-based delta sigma modulation

Li Zhao, Sicong Xu, Mingxu Wang, Bohan Sang, Jianyu Long, Long Zhang, Wen Zhou, Kaihui Wang, and Jianjun Yu
Opt. Lett. 48(6) 1450-1453 (2023)

SNR-enhanced signal delivery scheme with delta–sigma modulation in a four-mode fiber system

Jianyu Long, Chen Wang, Bohan Sang, Junjie Ding, Kaihui Wang, Bowen Zhu, Tianqi Zheng, Wen Zhou, Bing Ye, Weizhang Chen, Bo Liu, Lei Shen, and Jianjun Yu
Opt. Lett. 48(23) 6287-6290 (2023)