Investigation On Chaotic Synchronization Characteristics Based On Two Unidirectional Coupled Weak-resonant-cavity Fabry-perot Laser Diodes

With the progress of the times,the amount of information is increasing,and traditional communication systems face the challenges of transmission rate and communication capacity.The wavelength division multiplexing(WDM)technology has attracted considerable attention for greatly increasing the capacity of communication system,and it has been gradually applied to existing fiber-optic communication system.One of the most important factor for WDM technology is needed that the light source with different wavelengths to provide carriers for different channels.In recent years,the weak cavity Fabry-Perot laser(WRC-FPLD)has attracted much attention due to its great application prospects in WDM systems.Compared with the traditional Fabry-Perot laser(FPLD),the front face of the WRC-FPLD achieves a lower reflectance(1%~10%)by coating an anti-reflection coating,and a wider gain spectrum can be obtained.Externally light can be injected into the laser more efficiently.In addition,the long cavity length(300 ?m ~ 600 ?m)of the WRC-FPLD effectively reduces the longitudinal mode spacing.In particular,the WRC-FPLD can output a chaotic carrier with tunable central wavelength under appropriate external disturbance.Therefore,researching on obtaining chaotic carrier based on WRC-FPLD under external disturbance and corresponding chaotic synchronization characteristics is excepcted to promote the development and application of WDM chaotic secure communication.We experimentally studied a wavelength-tunable chaos synchronization for different corresponding modes of two unidirectionally coupled weak-resonant-cavity Fabray-Perot laser diodes(WRC-FPLDs).The master WRC-FPLD(M-WRC-FPLD)can obtain central wavelength tunable chaotic carrier signal under appropriate filtered optical feedback.The chaotic signals output with the wavelength of 1550.110 nm,1556.080 nm,and 1551.250 nm from M-WRC-FPLD,respectively,is unidirectionally injected into another slave WRC-FPLD(S-WRC-FPLD),the S-WRC-FPLD can output the same wavelength chaotic signal,and high-quality synchronization can be achieved between corresponding modes,the maximal correlation coefficient of chaotic system can reach 0.904.The experimental results show that when the injection power is large enough and keeps constant,the system can obtain the best synchronization effects when the frequency detuning is around-25 GHz.When the frequency detuning is kept constant,when the injection power exceeds 0.2 mW,the synchronization effect of the system no longer increases as the injection power increases.The best bias current of the slave laser is around 21 mA and the chaos system has a good synchronization effect,when the injection power is kept above 0.2 mW and the frequency detuning remains around-20 GHz.As for the chaotic signals with the wavelength of 1550.110 nm,1556.080 nm,and 1551.250 nm,the curves about the correlation coefficient with the influence of frequency detuning,injection power and bias current have the same trend,under appropriate parameters,the maximal correlation coefficient between three pairs of corresponding modes can exceed 0.900.