Hitless Tunable Filter Based On Microring Resonator And Its Wavelength Locking

With the development of information technology in modern society and the improvement of informationization,the demand for information exchange and communication has also increased.Optical interconnection technology uses waveguide mode to transmit data.It has low power consumption,ultra-low delay,extremely high communication bandwidth and minimal transmission loss.It has become an ideal on-chip interconnection technology.In current on-chip optical interconnection networks,wavelength signal rerouting is the key to optical information processing.This can be achieved by reconfigurable optical add-drop multiplexer(ROADM).Tunable microring resonator filter has the function of wavelength selection and is suitable for ROADM components.Traditional tunable filters block other wavelength channels when tuning the resonant wavelength,resulting in data loss.At the same time,because the working wavelength of the micro-ring resonator is limited at the resonant wavelength of the resonant cavity,the bandwidth is very narrow,and the devices based on micro-ring are very vulnerable to the thermal interference of the environment and the fabrication process.In this paper,the above two problems of micro-ring resonator are studied in depth.The main work includes the following aspects:1.Hitless tunable filter:Based on the principle of micro-ring resonator and Mach-Zehnder thermo-optic modulation,a wavelength switching hitless tunable filter is designed.The micro-ring resonator consists of two straight waveguides and a closed ring waveguide,which is used to construct a filter.The integrated heater on the ring is used to modulate the resonant wavelength.A part of the ring waveguide is coupled with another waveguide as an arm to form a Mach-Zehnder modulator,and an integrated heater on the other arm is used to modulate the light intensity in the ring.The experimental results show that a 25mW power signal is loaded on one arm of Mach-Zehnder modulator,and the filter is in working state,FSR = 2.18nm,and the loss of the drop port is 2.2dB.During the wavelength switching process,the output of drop port can be zero by raising the power of 25mW to 55MW,so that the transmission of the optical signal at the through port can not be interrupted and the hitless wavelength switching can be realized.2.Resonant wavelength locking of single micro-ring:A scheme of extracting spectral correlation information of micro-ring based on coherent detection is designed,and an anti-symmetric error signal is obtained.Resonant wavelength locking of single micro-ring is realized by threshold detection.Firstly,a spectrum information extraction scheme based on coherent detection is proposed.The extracted signal is an asymmetric error signal.The zero of the signal is the resonant wavelength of the micro-ring.The characteristics of the signal make it insensitive to the input power and can judge the drift direction of temperature,thus improving the speed and accuracy of locking.The signal extraction circuit and feedback algorithm are designed,and the whole feedback system is built.Experiments on a micro-ring resonator with a ring waveguide radius of 10 ?m and FSR=9.486 nm are carried out.The results show that the system can lock the micro-ring in the whole FSR.3.Resonant wavelength locking of double-ring resonator:A method of wavelength locking of double-ring resonator is designed.The error signals of each micro-ring are extracted by coherent detection principle.By adjusting the two rings separately,the two rings are locked separately.Firstly,the simulation analysis is carried out by using the software of Matlab.The feedback algorithms of flat-top micro-ring and subsidence micro-ring are proposed respectively.The fabricated double-ring is tested.The download spectrum of the micro-ring is flat-top.A signal extraction circuit and a feedback algorithm are designed for the device.The experimental results show that the system can lock the resonant wavelength of the double-ring resonator,and the system can still keep the resonant wavelength of the micro-loop stable when the temperature changes 30 K.