A novel optical frequency-hopping scheme based on a flexible structure for secure optical communications is proposed and demonstrated. In the proposed scheme, critical users' data are divided into a lot of segments, and these segments are transmitted by different optical wavelengths in time domain. In other words, one channel optical carrier carries different users' data segments. A flexible structure was demonstrated and used in optical frequency-hopping system to simplify the structure and decrease the cost of the security system. In this paper, the viability of a four-wavelength-frequency-hopping secure optical communication system with a 25-Gb/s error-free transmission through a 32-km single-mode fiber and a 8-km dispersion compensation fiber was demonstrated and verified by simulation tools.
The principle of wedge-crystal depolarizer was introduced and an optimal parameters combination of polarization direction, wedge angle, pupil size was obtained by using Mueller matrix. The design of depolarizer should be determined by crystal refraction index, wavelength, and incident pupil size. Calculation and simulation based on software show that degree of polarization (DOP) can be improved by increasing pupil size and wedge angle. Some significant conclusions for the optimized design of parameters were gained for fabricating crystal depolarizers.
In this paper, a hybrid optical frequency hopping system based on OAM multiplexing is proposed, which is mainly applied to the security of free space optical communication. In the proposed scheme, the segmented users’ data goes through two stages of hopping successively to realize data hiding. And the security performance is also analyzed in this paper.
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