The Dc-drift Control In The Integrated Optical Waveguide Pulsed Electric Field Sensor

Compared with the traditional electric field sensor, integrated optical waveguide electric field sensor has wide bandwidth, high sensitivity, high integration and would not be affected by electromagnetic environment. So, it has been widely applied in the field of pulsed electric field measurement. But in practice the optical waveguide sensor is also with the same trouble that the Mach-Zehnder(M-Z) interferometer electro-optic modulator is with, that is its working point will be affected by temperature, humidity, illumination and stress. Therefore, to provide a stable phase offset for the optical waveguide pulsed electric field sensor is very important.In this dissertation, an investigation and analysis of the dc-drift phenomenon existed in the practical application of the integrated optical waveguide pulsed-electric field sensor has been done. The scheme of using the feedback signal to tune the bias voltage of M-Z interferometer electro-optic modulator has been investigated experimentally, and the results show the dc-drift can be controlled effectively. Then, a scheme of tuning the operating wavelength so as to control the dc-drift of onedimensional(1-D) optical waveguide pulsed-electric field sensor has been investigated and confirmed. Furthermore, a three-dimensional(3-D) one has also been confirmed experimentally according to the same scheme. The main contents of the dissertation are as follows:Firstly, an analysis on the working principles of the M-Z interferometer electro-optic modulator, optical waveguide one-dimensional and three-dimensional pulsed electric field sensors has been presented. Then, the dc-drift mechanisms of optical waveguide 1-D and 3-D pulsed electric field sensors are analyzed.Secondly, for the M-Z interferometer electro-optic modulator with the characteristic of having modulation electrode and dc bias electrode, the method of adding perturbation signal has been adopted to control its dc-drift. Field Programmable Gate Array(FPGA) technology has been used to design the signal processing module and control module. It has been achieved to automatically control the electro-optic modulator’s dc-drift by feedback tuning the bias voltage with calculating the error signal from testing the peak value of the fundamental wave. Then, in view of the differences of electric field sensor and electro-optic modulator, the way of tuning laser’s operating wavelength to changing the phase difference of the two arms of the M-Z asymmetric structure is introduced to control the dc-drift of the 1-D pulsed electric field sensor.Finally, in order to solve the problem that a single operating wavelength cannot simultaneously satisfy to control the dc-drift of 3-D optical waveguide electric field sensor which consists of three 1-D sensors with different dc-drift characteristics, a sampling control system based on time division multiplexing has been designed to control the dc-drift of 3-D electric field sensors. Its structure and working principle are analyzed in detail and the simulation is also presented. Then, based on 1-D dc-drift control system, one for the 3-D sensor has also been designed and confirmed.