| The rapid development of wireless communications has provided the flexible and ubiquitous access for subscribers, but also brought about the challenges due to limited bandwidth resources. In order to meet the insistent demand for high capacity and more flexibility, the integration of optical fiber and wireless access is an inevitable trend of development. In this case, radio-over-fiber (ROF) has emerged as the technology to make full use of the advantages of fiber and wireless communications. It makes the complex equipment shifted to the central station, and thus greatly reduces the cost of base station, making it easier for the implement of small honeycombs. However, many issues and difficulties remain for ROF technology, such as improvement of spur-free dynamic range (SFDR) for analog-optical links, millimeter-wave frequency up and down-conversion, and the non-line of sigh (NOLS) of millimeter-wave transmission, etc.This thesis focuses on the research of millimeter-wave frequency up and down-conversion, and the main work includes several parts:(1) Carrying out an in-depth research of the lightning effect of lithium niobate modulator, a.k.a. Pockles and improving the theoretical model for modulator inhibit carrier based on an analysis of modulators in different situations; simulating the up-conversion of DBS modulation, OCS modulation as well as the cascade modulation of both on the basis of Mach-Zehnder's modulator; coming up with a high-frequency up-conversion program.(2) Simulating the down-conversion program based on MZM's DSB and OCS modulation; establishing ROF system to prove the feasibility of the frequency conversion plan; comparing the respective characteristics of several such plans. (3) Conducting a research on the non-linear characteristic of PCF material, then designing and simulating an up-conversion program on the basis of PCF four-wave mixing effect, with an analysis of variables that may influence the frequency conversion performance. |
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