Research On The Application Of Four-wave Mixing In Radio-over-Fiber System And All-optical Wavelength Conversion

Two major developing aspects exist in today’s communication networks. One is fiber-wireless mixing network. Radio-over-fiber system is one of the key technologies in future broadband wireless access. This dissertation researches on the key technologies and polarization sensitivity issues in the ROF system. We proposed using four-wave mixing (FWM) to realize a polarization insensitivity ROF system. The other developing aspect is all-optical network. All optical wavelength conversion (AOWC) is one of the key technologies in all-optical network and it can solve wavelength congestion problems. In optical communications, OFDM signals can resist to chromatic dispersion and polarization mode dispersion. Polarization multiplexing signals can increase communications capablities. Therefore, this dissertation has demonstrated AOWC for OFDM signal and polarization multiplexing signal based on FWM effect which is one of methods to carry out AOWC.This dissertation has theoretically and experimentally investigated the new applications of FWM in ROF system and AOWC. It is of great significance in both theory and practice in future communications. We obtained the following results:First, one scheme based on multi-cascaded intensity modulations to generate multiplicated milimeter-wave is proposed. We theoretically studied the general rule of this scheme. Based on this rule, we built a40GHz mm-wave ROF system using two cascaded intensity modulators to transmit base signals. We found that by adjusting the phase and the repetitive frequency coe of the driven RF signal between modulators (n), we can obtain mm-wave with a certain high-spectrum-purity frequency of2nωe. We considered two cases in order to analyze this rule including infinite extinction rate (ER) and finite ER. The experiment is constructed to verify this rule in generating octupling frequency mm-wave signal using three cascaded intensity modulators. A ROF-WDM-PON system is built up to provide triple service based on integrated modulator.Second, we have proposed and experimentally demonstrated a novel polarization insensitive all-optical up-conversion for multiplicated milimeter-wave ROF system based on FWM in SOA.Using odd-sideband suppression and optical carrier suppress (OCS) method to generate two sidebands. The generated two sidebands have the parallel polarization direction and phase locked. Because the dual-pump FWM AOWC system is polarization insensitive, ROF system can use this technique to realize polarization insensitive and avoid using too many polarization controllers to control light transmission. This technique can reduce the system complexity and cost. The power penalties of the two schemes are low. Therefore, the AOWC technique applied in ROF system is an effective method to carry out polarization insensitivity.Third, we have theoretically and experimentally demonstrated AOWC for orthogonal frequency division multiplexing (OFDM) signal based on the FWM effect.We have theoretically and experimentally investigated three AOWC configurations for OFDM signal based on FWM in single pump, parallel pump, and orthogonal pump configurations, respectively. The AOWC configurations based on single-pump for OFDM signal is polarization sensitive, and the converted lightwave with OFDM signal is obained nearby the original signal lightwave. The spectrum of the converted OFDM signal is inversed with the original one. The AOWC configurations based on dual-pump for OFDM signal is polarization insensitive. And the factors which effect system conversion efficiency are discussed.Last, we have theoretically and experimentally analyzed AOWC for polarization multiplexing signal based on the FWM effect. The condition of receiving polarization multiplexing signal without crosstalk is deduced.We have theoretically and experimentally analyzed AOWC based on four-wave mixing with orthogonal pumps for polarization multiplexing signals in highly nonlinear fiber. In the parallel pump configuration two polarization reference frames are discussed and the same results are obtained. We found the condition of receiving polarization multiplexing signal without crosstalk. We also theoretically analyzed AOWC for polarization multiplexing signals in a SOA. The condition of receiving polarization multiplexing signal without crosstalk and effect factor of conversion efficiency are deduced and analyzed.