The Research On A New Type Of Reflective Traveling Wave Electro-optic Modulator And It's Drive Technology

In the era of rapid development of the Internet,demand for the bandwidth is increasing,which promote the development of optical fiber communication.In the commercial optical communication systems,coherent optical communication has replaced traditional optical fiber communication which is uesed the intensity modulation / direct demodulation technology.In terms of its system performance,the synchronous coherent optical communication system is the best solution,but the difficulty to build up the optical phase-locked loop.In order to solve this problem,we present a modified synchronous homodyne coherent reception system.According to the demand of the system,a novel reflective structure of lithium niobate traveling wave electro-optical modulator is proposed.In this paper,the basic principle of the improved synchronous homodyne coherent reception system is briefly introduced.We introduce the reflective traveling wave electro-optical modulator which is an important part of the system.According to the characteristics of the reflective structure,we provide the analysis model of the signal.According to the actual system requirements,only the reverse modulation part is used and the forward modulation is regarded as noise.We discuss the rule of total phase shift change and the influence of forward modulation noise on phase modulation in detail.Using the conformal transformation(SC)toolbox under Matlab,the key parameters of the reflection modulator are simulated and analyzed.By increasing the thickness of the electrode,the buffer layer with low refractive index of the physical medium,increase the thickness of the buffer layer and other measures can effectively change the performance of reflective electro-optical traveling wave modulator.However,there are some restrictions in the key parameters of the modulator such as the equivalent refractive index,the characteristic impedance,the conductor loss,the half-wave electrode and so on.To combine the performance of the reflective modulator,we take into account the value of the key parameters.Through simulation results,we find hat the change of the key parameters of the modulator is independent of the reflective structure.A simple driver circuit of a differential amplifier based on Texas Instruments is shown.The drive circuit can achieve a small signal distortion-free amplification and meet the impedance matching.According to the characteristics of the reflective electro-optical traveling wave modulator,an improved synchronous homodyne coherent reception system is proposed.Using the OptiSystem,the two-phase shift keying(BPSK)and the Quadrature Phase Shift Keying(QPSK)system based on the improved synchronous homodyne coherent reception system are simulated respectively.Through the analysis of the system's constellation,eye diagram,Q factor,etc.,the system performance is well.In the scope of system error tolerance,it can complete the corresponding phase modulation and demodulation.The improved synchronous homodyne coherent reception system ensures that the lasers are the same as the local oscillators.So the performance of each other is exactly the same,the phase difference is stable and the effect of synchronization is realized,which solves the problem that the optical phase-locked loop is difficult to realize.