Principle And Circuit Design Of A Novel EO Modulator

High-speed optical communication systems are flourishing at present, as one of the key components, High-speed electro-optical modulators will have great influence on the quality of optical communications. By far their price are still thousands of US dollars which prevent their widely use in optical fiber communication system seriously. Therefore, to develop a new type of high-speed electro-optical modulator with high performance and low-cost has become a hot spot for international research.In this thesis, a low loss, low voltage, polarization independent high speed EO polymer modulator based on tunable micro-ring resonator is presented. The major research work focuses on the design and optimization of the bias circuit of this novel polymer EO modulator. The main achievements are as follows.1. The transfer function of single waveguide coupled to a micro-ring resonator and two waveguide coupled to a micro-ring resonator is calculated using the coupled mode theory, and electro-optical modulators based on micro-ring resonator are analyzed. The extensive application in photoelectronic device domain and process technology of micro-ring resonator is also elaborated.2. The feature of HBT device which make it suitable for making the driver circuit of optical modulators is explained , and a type of driver circuit of optical modulators using HBT device is analyzed, according to its technical target we consider that it is suitable for loading on the new type of High-speed electro-optical modulators.3. The optimum bias voltage of optical modulators is unstable, it will drift with the variation of circumstance temperature and other reasons, this will worsen the output signal, but if the bias voltage is reasonably set up, the CSO(Composite Second Order Distortion) can be eliminated.4. On the base of theory analysis, the bias voltage circuit of optical modulator based on micro-ring resonator is designed, it includes reference voltage module and digital control module. Reference voltage module provides the reference voltage of D/A converter; digital control module can achieve digital control.5. The designed bias circuit is simulated. All the simulation results proved that this circuit can provide stable DC bias voltage and the function of temperature feedback can keep the DC bias voltage around the optimum bias point all the time, otherwise, this circuit can give the protection of overcurrent and digital control is achieved.