Optical access transmission with improved channel capacity using non-orthogonal frequency quadrature amplitude modulation

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• 作者：Yong-Yuk Won ; Sang Min Yoon ; Dongsun Seo
• 关键词：Non ; orthogonal frequency quadrature amplitude modulation ; Non ; orthogonal frequency shift keying ; Optical access transmission ; Quadrature amplitude modulation
• 刊名：Optical and Quantum Electronics
• 出版年：2017
• 出版时间：February 2017
• 年：2017
• 卷：49
• 期：2
• 全文大小：
• 刊物主题：Optics, Lasers, Photonics, Optical Devices; Electrical Engineering; Characterization and Evaluation of Materials; Computer Communication Networks;
• 出版者：Springer US
• ISSN：1572-817X
• 卷排序：49

文摘

A new modulation scheme that improves the bandwidth efficiency of an optical access link is proposed in this paper. It is implemented using non-orthogonal frequency shift keying (FSK) and quadrature amplitude modulation (QAM) simultaneously. We call the proposed technique non-orthogonal frequency quadrature amplitude modulation (NOFQAM). Especially, non-orthogonal FSK based on digital signal processing (DSP) is proposed for the first time. DSP-aided non-orthogonal FSK allows us to select RF carrier frequency irrespective of the channel bandwidth to allocate FSK symbols, unlike the existing orthogonal FSK. The non-orthogonality is implemented using a sequential correlation, where a received NOFQAM signal is correlated with only one RF carrier at a time by using DSP. After the sequential correlation is completed, both the FSK and the QAM symbols are recovered successfully and merged to generate the NOFQAM symbols. For experimental verification, a 20-km optical access link, which can transmit a 64-NOFQAM signal sampled at 10 Gsample/s, is implemented. We observed no increase in occupied channel bandwidth and a power penalty <0.5 dB compared to the 16-QAM scheme. A bit error rate lower than 10−11 was obtained for the frequency spacing considered herein, which corresponds to 3% of the used RF carrier (1.5 GHz) when there are 50 sampling points per 64-NOFQAM symbol.