Abstract
A new laser system is suggested and experimentally verified as a chaotic transmitter for a secure optical communication system. The laser source kind is a distributed feedback with a peak wavelength 1310nm and maximum power 5mW. A doubly external cavity with 85cm of length is constructed via air.Chaotic signal is achieved successfully after the laser reach of coherence collapse, with a very wide band spectrum (12GHz). This value is capable to increase subjecting to several parameters based on optical feedback (OFB) such as laser current operating level, beam focusing, polarization control, etc. In order to test a message hiding possibility, a frequency message is modulated directly into the laser, which is connected with the laser source using a bias tee. For the free running (solitary) semiconductor laser, the maximum available direct current modulation is: 3GHz/mA, while this value can be increased by this technique. This gives the possibility for very high modulation values and increasing data package volume that can send securely in the applications that requires immunity.
Highlights
Modulation with Semiconductor LaserDirect modulation into semiconductor laser (SL) represents one technique for chaos generation (CG)
A new laser system is suggested and experimentally verified as a chaotic transmitter for a secure optical communication system
Chaotic dynamics is typically observed through the quasi periodicity route to chaos linearly related to strength of frequency external modulation [1]
Summary
Direct modulation into semiconductor laser (SL) represents one technique for chaos generation (CG). 2. Semiconductor Laser with Optical Feedback OFB, alternative name to it is self-mixing interference, means change in both laser intensity and polarization states with a small fraction of the output laser re-injected the laser cavity. [5] suggested a model employing uses lateral OFB of slow light to enhance the modulation bandwidth of a SL of type ‘vertical cavity surface emitting laser (VCSELs)’ with increasing modulation bandwidth up to 40 GHz. Ref. Power attenuation, nonlinearity inserted externally into the delayed beam, amplification all can be changed to enrich these dynamics [10] and even inserting acoust-optic modulators to achieve frequency-shifted OFB measurements using a solid-state microchip laser (for sensing applications) [11]. The model of external cavity is shown in figure 2, where ݎଶ is the internal cavity back mirror reflectivity, ݎ is the internal cavity front mirror reflectivity, and ݎଷ external cavity mirror reflectivity [12]
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