The difference between the initial wavelength of the output signal caused by the error during the tunable laser tuning process will lead to the decrease of the azimuth resolution of the synthetic aperture lidar. In order to reduce the initial wavelength error, a scheme of filtering using a cascaded micro-ring M-Z optical band-pass filter is proposed. Using the digital filter design method by cascade micro-loop assisted M-Z interferometer to achieve elliptic filter. The 24-order elliptic filter is used to realize the filter with the transition band of 0.001nm, the passband ripple of 1dB and the stopband ripple of 60dB. The use of digital filter design cascaded micro-ring M-Z interferometer optical filter, not only to achieve the desired results, but also can improve the design efficiency of optical filters. After the optimization of the parameters of the cascaded microring M-Z filter, a filter with a large bandwidth, a flat top and a very small transition band can be obtained. Used to control the initial wavelength error can achieve the desired effect.
In the application of aperture laser radar, in order to improve the range resolution of image, in general adopting linear modulation signal. But in practice, the transmitting signal of tunable laser is linear wavelength modulation. In order to make clear the effect of linearity of tunable laser to the quality of synthetic aperture laser radar’s image, the expression of linearity of linear wavelength modulation signal has been developed according to the definition of linearity and the effect of linear wavelength modulation signal to the quality of synthetic aperture laser radar’s image has been analyzed. The result shows that the same influence trend that with the pulse during time and coefficient of wavelength-modulated increase, the linearity increase and the quality of synthetic aperture laser radar’s image deteriorate and that the increasing carrier wavelength do the reverse. And further a step, the linearity and the quality of synthetic aperture laser radar’s image have been positive correlative, so the linearity deteriorates the range resolution of laser radar.