Research On A Narrow-bandwidth Tunable Optical Filter With Ultra-wide Tuning Range

With the application of 5G communication technology and the demand of massive data transmission,the requirements for optical fiber communication technology and optical information processing technology are getting higher and higher.Tunable optical filter(TOF)is the core device for optical performance monitor(OPM).The trend of TOF is shorter response time,wider tuning range,miniaturization and technical standardization.This paper studies narrow-band tunable optical filter based on free-space optics and employing MEMS(micro electro mechanical systems)and grating.The main contents are as follows:A narrow-band TOF with wide tuning range is designed based on MEMS technology.The wide spectrum signal is split into two sub-bands by the combination of a 1 × 2 port optical switch and a arrayed waveguide.Under the control of the optical switch,the two sub-band optical signals are time-shared and incident on the grating at different angles.The whole freespace optical system consisting of a MEMS micro mirror,a grating,a collimating lens and a compression lens is shared by the two sub-band optical signals.Based on the Gauss field model,the relationship between the filter spectrum of the TOF and the parameters of the elements is simulated and analyzed.According to the results,the TOF structural parameters are designed,which meets the requirements by an OPM for the transmission system with channel spacing of 50 GHz.The parameters are further optimized by ZEMAX software modeling and simulation.According to the simulation results,the optical elements and mechanical parts for the verification experiment are designed and fabricated.An experimental platform is built to test the performance of the above designed TOF.The results show that the insertion loss for C-band(1530?1570nm)center wavelength is 3.36 d B,3d B-linewidth is 0.168 nm,20d B-linewidth is 0.544 nm,crosstalk is less than-30 d B;the insertion loss for L-band(1570?1603nm)center wavelength is 5.37 d B,3d B-linewidth is0.158 nm,20d B-linewidth is 0.352 nm,crosstalk is less than-30 d B.