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Research Of Microwave Signals Generation And Transmission With Photonic Method

Posted on:2017-02-11Degree:MasterType:Thesis
Country:ChinaCandidate:Y F SunFull Text:PDF
GTID:2308330485483328Subject:Communication and Information System
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With the progress of modern science and technology, the technical demand needs to be enhanced, the microwave transmission and the fiber technology merged gradually, which give us to a new domain—microwave photonics. Compared with traditional techniques, the fiber technology has the advantages of light weight, less volume, low transmission loss, large band and better anti-EM interference, etc. It holds significant position in many areas, such as large data communication, large power radar system and electronic warfare. The production of high quality microwave signals is especially important in microwave systems. Furthermore, the microwave photonic links have the both advantages of microwave communication and fiber communication, which has extensive applications in high capacity and large data transmission.At the very first, this paper gives us a brief introduction of the common implements and principle of microwave photonics, which highlights the principle of phase modulator, Mach-Zehnder modulator (MZM) and photodetector. Then we studied the present research situation of the microwave production with photonic methods, a summary about the working principle of main photonic microwave signal generation techniques. Afterwards, a brief introduction, which is about the microwave photonic links and the main index of the link performance, was given.Secondly, based on the research of microwave multiplication, we proposed a new scheme of photonic microwave signal generation, which is mainly based on a MZM and four-wave-mixing (FWM). The light emitted from a laser is firstly intensity modulated by a MZM, which give birth to two first-order sidebands. These two 1st-order sidebands satisfy the phase-matching condition, which can generate two 3rd-order sidebands through FWM. After produced by a tunable optical filter and an optical loop, the two 3rd-order sidebands will be reserved and sent back to the same nonlinear medium to perform the second FWM process after passing a polarization controller(PC), the PC is used to adjust the polarization of the two 3rd-order sidebands to let their polarizations perpendicular to the first FWM process. The 2nd FWM process will give birth to two 9th-order sidebands, after filtered by an interleaver, the two 9th-order sidebands will be kept and sent to a photodetector(PD), then a microwave of 18 times of that input microwave signal will be achieved. This scheme combines the FWM with external modulation technics, a higher multiplication factor 18 is achieved by using two FWM process in one nonlinear medium.In the end, a research of phase modulation links’nonlinear distortion is studied and analyzed, after theoretic analyzed about the PD module, for the propose of reducing the influence of 2nd-order nonlinear distortion generated by PD in PM fiber links, we build a new photonic program to improve the link performance. This scheme takes advantage of the two polarization axis of PM, single-sideband PM optical spectrum was obtained by using a polarizer and a tunable optical filter, accompanied with the direct detection method, this scheme decreased the PD-reduced 2nd-order nonlinear distortion effect significantly. Experimentally verified by adjusting the polarization angle of PM spectrum, this scheme highly improved the PM link performance.
Keywords/Search Tags:Frequency multiplication, Four-wave-mixing (FWM), Photodetector (PD), Nonlinear effect, Second-order harmonic suppression, Phase-Modulation (PM) links
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