利用非零色散位移光纖研究分佈式拉曼放大器之四波混合效應; Study of Four-Wave Mixing Effect in Distributed Raman Amplifier by Utilizing a Non-Zero Dispersion Shifted Fiber

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Title:	利用非零色散位移光纖研究分佈式拉曼放大器之四波混合效應;Study of Four-Wave Mixing Effect in Distributed Raman Amplifier by Utilizing a Non-Zero Dispersion Shifted Fiber
Authors:	龔祖德;Kung,Tsu-Te
Contributors:	機械工程學系
Keywords:	四波混合;分佈式拉曼放大器;非零色散位移光纖;Fou-wave mixing;Distributed Raman Amplifier;Non-zero dispersion shifted fiber
Date:	2013-07-29
Issue Date:	2013-08-22 12:14:45 (UTC+8)
Publisher:	國立中央大學
Abstract:	本論文分別從理論和實驗的層面上，利用非零色散位移光纖研究前向激勵光波中的法布里－珀羅多模態和單一波長信號光波之四波混合現象。經由四波混合效應，可發現中心波長在14xx奈米之100毫瓦多模態激勵光波會在單一波長15xx 奈米之1毫瓦信號光波旁，產生多模態的分佈。其中歸納出，要發生最大四波混合效率之第一條件為激勵光波和信號光波擁有相同之群折射率；第二條件為調整信號光波之波長映射至激勵光波中擁有最大相鄰功率模態之中心波長。在最大四波混合效率的條件下，取信號光波長和激勵光中心波長之中間值，則可得到非零色散位移光纖之零色散波長。在一利用非零色散位移光纖之分佈式拉曼放大器架構中，在14xx奈米之激勵光波和15xx奈米之信號光波的群折射率相同時，可以得到最大之四波混合效率，同時也會造成信號光波在此波長的拉曼放大器增益被壓抑了2至3分貝。若激勵光波和信號光波之群折射率不相同時，則四波混合導致信號光波旁產生之多模態分佈明顯地變少，此為四波混合效率降低所致。信號光波和產生四波混合之最大旁波之比率，在本論文中定義為四波混合產生功率比。在不考慮自相位調變和交互相位調變的簡化條件下，所得之四波混合產生功率比和信號光波之強度是無關的。本論文中更進一步利用非線性薛丁格方程式，包含激勵光波和信號光波之自相位調變和交互相位調變的效應，對於不同信號光波強度下，重新推導四波混合效率及四波混合產生功率比之關係式是和信號光波之強度相關的。將此一理論研究，和所設計之實驗實際測量四波混合產生功率比時，發現會受到受激布里淵散射之影響，在信號光波旁出現受激布里淵散射的回散射旁帶信號。所以為避開受激布里淵散射之產生，將最大信號光功率設定在12毫瓦，依然可以得到理論和實驗的強度相關四波混合功率產生比的誤差為0.12分貝，證實了理論推導之強度相關四波混合之適用性。 In this dissertation, the four-wave mixing (FWM) is studied theoretically and experimentally between the co-propagated pump Fabry-Perot (FP) modes of a FP laser diode (FPLD) and the single wavelength probe signal in a non-zero dispersion shifted fiber (NZDSF). The 100 mW co-propagated FP spectra centered at 14xx nm are reproduced via FWM around the 1 mW single wavelength signal around 15xx nm. The maximum FWM efficiency is found to have the first condition in matching of the group indices between the pump and signal. And the second condition is mapping the signal wavelength to the center wavelength of the FP pump modes to have the adjacent FP modes with larger powers. The zero-dispersion wavelength of NZDSF can also be determined at the middle of the signal and the center wavelength of pump to have the maximum FWM efficiency. The FWM between 14xx nm pump and 15xx nm signal in a forward-pumped distributed Raman amplifier (DRA) through a NZDSF was also observed experimentally. The suppression of DRA gain by about 2 to 3 dB was experimentally observed with maximum FWM at minimum phase mismatching between 14xx nm pump and 15xx nm signal waves. If the group indices between pump and signal are different, the FWM reproduced FP spectra beside the signal will be dramatically reduced due to the less FWM efficiency. The FWM generated power ratio (FWMGPR) is defined as the power ratio between the original signal and the maximum FWM generated signal. Neglect the self phase modulation (SPM) and cross phase modulation (XPM) between the pump and signal, the FWMGPR is unrelated with the intensity of the signal. For further study the FWMGPR, the intensity-dependent FWM efficiency is derived by the nonlinear Schrodinger equations including the SPM and XPM between the two FP modes of a pump and a single-wavelength signal. It is found that the experimental measurement for the FWMGPR is limited by the stimulated Brillouin scattering (SBS). Under the threshold of SBS, the experimental results are still coincided well with the theoretical calculations of the FWMGPR to have the difference of 0.12 dB for the input signal power of 12 mW.
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