| With the development of optical communication,tunable lasers have been key components of modern optical fiber communication systems,and used in dense wavelength division multiplexing systems and next-generation reconfigurable optical networks.Over the past few decades,researchers have developed numerous monolithic or hybrid integrated tunable lasers using electrical,mechanical or thermal tuning methods.For monolithic widely tunable lasers,complex characterization and control have always been the biggest obstacle restricting its practical application.Therefore,many researches are dedicated to studying simple characterization methods and robust feedback algorithms.In this dissertation,the characterization and control of monolithic integrated multi-channel interference(MCI)widely tunable lasers are systematically studied.The main contents are as follows:(1)A characterization method based on shifting longitudinal mode-aligning phase is proposed,and the quasi-continuous tuning of electrically tuned MCI laser is realized by this method.In order to align the phases of eight arms,an arm phase alignment algorithm based on hill-climbing algorithm is proposed.The longitudinal mode is shifted with a longitudinal mode interval through the common phase section,and the arm phase alignment algorithm is used to optimize each arm to align the phase.The process of shifting longitudinal modealigning phase is repeated,ultimately achieving a qusi-continuous tuning range over 48 nm.In the entire tuning range,the wavelength deviations are less than ±8 pm,the side mode suppression ratios(SMSRs)are greater than 40 d B and the Lorentzian linewidths are less than 350 k Hz.(2)In order to solve the problem that the characterization method based on shifting longitudinal mode-aligning phase is limited by the longitudinal mode interval,a fast characterization method based on phase interpolation is proposed,which realizes the quasicontinuous tuning of the thermally tuned MCI laser.The reflection peak at any wavelength is obtained by phase interpolation,and the reflection peak is optimized by using the arm phase alignment algorithm.The longitudinal mode is adjusted to the center of the nonhysteresis interval through the common phase section.Finally,a qusi-continuous tuning range over 60 nm is achieved with wavelength deviations less than ±10 pm,SMSRs greater than 40 d B and Lorentzian linewidths less than 100 k Hz.(3)In order to realize the long-term stable operation of the MCI laser,a feedback control scheme of power,frequency and mode is proposed.The precise control of the output power is realized by adjusting the injection current in the semiconductor optical amplifier(SOA)section,and the power fluctuation is less than 0.1 d B.The frequency locking is realized by controlling the injection current in the common phase section,and the locking range is about one longitudinal mode interval.The locking of the reflection peak is realized by locking the phase slope of each arm,and the locking range exceeds two longitudinal mode intervals.In addition,the influence of environmental changes and device aging on the reflection peak is analyzed,and the stability of the reflection peak is tested.(4)Based on the proposed characterization method and control scheme,the MCI widely tunable laser integrated assembly is characterized and controlled.The overall framework of the integrated assembly is introduced,which includes ten control currents and multiple control loops.The key optical parameters involved in feedback locking and wavelength switching are analyzed in detail.And the characterization and control of the integrated assembly are demonstrated.The integrated assembly has a quasi-continuous tuning range cover the C++ band with SMSRs greater than 46 d B,frequency deviations less than ±0.5 GHz,output powers higher than 45 m W and Lorentzian linewidths lower than200 k Hz.Moreover,the integrated assembly has the functions of power control and frequency locking,as well as the function of shutting off-extinction during wavelength switching.And it meets industry requirements in terms of size,performance and power consumption. |
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