Research On Multiwavelength Chaotic Laser Of Semiconductor Optical Amplified Fiber Ring Laser

With the advancement of information technology,society has already entered the Internet information era.In this era,the security of personal information and the confidentiality of communications are the problems that are receiving much attention.Information hiding is one of the key technologies in the communication transmission process.By hiding important information in the carrier signal,the purpose of confidential information transmission is achieved.A chaotic signal is a special noiselike deterministic signal generated in a certain nonlinear physical system.Its state is determined by the initial value of the system.Compared with a typical deterministic signal,its temporal waveform appears as if it is random.However,it is predictable when the initial value is known.Chaotic optical signal can be used as the carrier of information transmission in secure optical communication.Therefore,research on the generation of chaotic signals in the optical domain is very important.Semiconductor lasers can realize chaotic lasing with simple configuration.However,due to the structural characteristics of the semiconductor lasers,broadband wavelength tuning and multi-wavelength chaotic emission is difficult.To solve the problem of wavelength flexibility,semiconductor optical amplifier(SOA)based fiber ring lasers are investigated,aiming at achieving broadband wavelength tunability and multi-wavelength chaotic lasing,which would satisfy the requirement for wavelengthflexible chaotic light sources in the future wavelength division multiplexed chaotic communication systems.In this thesis,the following research works are carried out:(1)The methods of chaotic signal analysis are studied.The randomness of the signals is initially verified based on the autocorrelation result and the power spectrum.The binary amplitude mapping method is used to generate a random sequence from the signals.NIST SP800-22 is used to test the randomness of the sequence,and the random quality of the signal is obtained according to the test.Furthermore,the method for the calculation of the maximum Lyapunov exponent is studied and realized based on phasespace reconstruction.(2)SOA-based fiber ring laser capable of optical chaos generation is demonstrated experimentally.The chaotic nature of the laser output is verified using analysis methods studied in(1).Besides,the independence of the chaotic signals carried by the two orthogonal polarizations of the lasing output is verified,and that of the chaotic signals generated in the two opposite directions of the laser cavity is verified too.(3)By inserting a wavelength-and bandwidth-tunable optical bandpass filter into the SOA-based fiber ring laser cavity,the chaotic characteristics of the output signal investigated.The chaotic laser can achieve continuous wavelength tuning from 1540 nm to 1560 nm.The chaotic nature can be maintained as long as the bandwidth of the optical bandpass filter is no less than 1.5 nm.A dual-wavelength chaotic laser is achieved based on a two-cavity scheme.The chaotic nature and the independence of the two output signals are verified.Parallel lasing of four wavelengths is achieved by incorporating four wavelength-division multiplexed fiber Bragg gratings.The chaotic nature and the independence of the two output signals are verified,too.The maximum number of parallel chaotic lasing outputs is estimated two be twelve with the current experimental configuration.