{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,21]],"date-time":"2026-03-21T17:49:56Z","timestamp":1774115396106,"version":"3.50.1"},"reference-count":24,"publisher":"MDPI AG","issue":"18","license":[{"start":{"date-parts":[[2023,9,20]],"date-time":"2023-09-20T00:00:00Z","timestamp":1695168000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Key R&amp;D Plan of the Ministry of Science and Technology of China","award":["2022YFB3606600"],"award-info":[{"award-number":["2022YFB3606600"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>In this work, we propose a bipolar complementary pulse width modulation strategy based on the differential signaling system, and the modulation\u2013demodulation methods are introduced in detail. The proposed modulation\u2013demodulation strategy can effectively identify each symbol\u2019s start and end time so that the transmitter and receiver can maintain correct bit synchronization. The system with differential signaling has the advantages of not requiring channel state information and reducing background radiation. To further reduce the noise in the system, a multi-bandpass spectrum noise reduction method is proposed according to the spectrum characteristics of the received modulation signals. The proposed modulation method has an error bit rate of 10\u22125 at a signal-to-noise ratio of 7 dB. The fabricated optical communication system can stably transfer voice and text over a distance of 5.6 km.<\/jats:p>","DOI":"10.3390\/s23187988","type":"journal-article","created":{"date-parts":[[2023,9,20]],"date-time":"2023-09-20T22:38:45Z","timestamp":1695249525000},"page":"7988","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":7,"title":["A Free-Space Optical Communication System Based on Bipolar Complementary Pulse Width Modulation"],"prefix":"10.3390","volume":"23","author":[{"given":"Jinji","family":"Zheng","sequence":"first","affiliation":[{"name":"School of Electronic Science and Engineering, Nanjing University, Nanjing 210023, China"}]},{"given":"Xicai","family":"Li","sequence":"additional","affiliation":[{"name":"School of Electronic Science and Engineering, Nanjing University, Nanjing 210023, China"}]},{"given":"Qinqin","family":"Wu","sequence":"additional","affiliation":[{"name":"Electronic & Information Engineering, Nanjing University of Information Science & Technology, Nanjing 210044, China"}]},{"given":"Yuanqin","family":"Wang","sequence":"additional","affiliation":[{"name":"School of Electronic Science and Engineering, Nanjing University, Nanjing 210023, China"}]}],"member":"1968","published-online":{"date-parts":[[2023,9,20]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"2951","DOI":"10.1007\/s11277-021-08380-9","article-title":"Free space optics, channel models and hybrid modulation schemes: A review","volume":"119","author":"Magidi","year":"2021","journal-title":"Wireless Pers. 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