Ring And Phase Module Assisted Mach-Zehnder Modulator For ROF System

The electrooptic intensity modulator used in Radio-over-Fiber system needs to have high linearity transmission. While the Ring and phase module assisted Mach-Zehnder modulator (RPAMZM) have a simply structure and a high linearity transfer function, and is not limited by the electronic speed, RPAMZM can be used in ROF system to restrain the channel cross talk generated while using the sub-carrier modulation technique. Supported by the 973 Project of China (Microwave Photonic Filter, Grant No. 2006CB320805), analysis for RPAMZM are presented in this thesis. The main contents are listed as follows:(1) The research signification of the ROF is stated. The function of linearity modulator is introduced.(2) Analysis for designing electrooptic modulators is included.(3) Summaries for increasing the linearity of Mach-Zehnder modulators under electronic and optical methods are presented.(4) The principle of microring resonators is analyzed. By introducing a microring and a phase modulator to each arm of a Mach-Zehnder modulator, a new linearity intensity modulator, named Ring and PM assisted Mach-Zehnder modulator (RPAMZM), is designed, which can compensate the sublinear property of Mach-Zehnder modulators.(5) Analyses under loss-less condition, loss condition and Spurious Free Dynamic Range (SFDR) are proposed. It is found that the nonlinearity under loss-less condition mainly comes from the 3rd terms of the Taylor series of modulator's transmission function. By properly setting the coupling coefficient, this term can be zero and a high linearity can be reached. A corresponding SFDR of 19.68dB can be achieved. On the other hand, when loss is considered, the main nonlinear terms, including the 2nd and the 3rd term, can be eliminated by properly setting the coupling coefficient and bias point. A corresponding SFDR of 15.74dB can be achieved. The bandwidth property of the modulator is also involved in this thesis.