Design and Investigation of 10 Gb/s FSO Wiretap Channel Using OCDMA Time-Diversity Reception

• Published in: IEEE photonics journal Vol. 12; no. 3; pp. 1 - 12
• Main Authors: Ji, Jianhua, Wu, Bing, Zhang, Jianjia, Xu, Ming, Wang, Ke
• Format: Journal Article
• Language: English
• Published: Piscataway IEEE 01.06.2020; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Atmospheric turbulence; Bit error rate; Code Division Multiple Access; Coders; Delay lines; Electronic surveillance; free space optical communication; Optical attenuators; OPTICAL code division multiple access; Optical coupling; Optical encoders; Optical fibers; Optical pulses; Optical receivers; Reliability aspects; Security; security capacity; Switches; time-diversity; Turbulence; Wiretapping
• ISSN: 1943-0655; 1943-0655; 1943-0647
• DOI: 10.1109/JPHOT.2020.2985747

In this paper, 10 Gb/s free space optical (FSO) wiretap channel using optical code division multiple access (OCDMA) time-diversity reception is designed and demonstrated for the first time. Reliability and security are investigated under weak and strong turbulence conditions. Two-dimensional optical encoder and decoder are constructed by wavelength selective switches and optical delay lines, and one-dimensional optical encoder and decoder are constructed by couplers and tunable optical delay lines. Experimental results show that reliability and security can be enhanced simultaneously using OCDMA time-diversity reception. At the received power of 2.58 dBm in strong turbulence, compared to non-diversity system, bit error rate (BER) of legitimate user in OCDMA time-diversity system is reduced from 3.9 × 10 −7 to 6.73 × 10 −8 . Furthermore, the reliability improvement is more obvious when the correlation between the two signals of OCDMA time-diversity is smaller. The secrecy capacity can be increased from 0.546 bit/symbol to 0.665 bit/symbol in strong turbulence when received power is 2.28 dBm. On the other hand, the secrecy capacity of strong turbulence is about 15% higher than that of weak turbulence.