The predissociation of the v=9 level in the b^3Пg state by the 3∑u^＋ state of helium eximer （He2） was studied based on the newly observed （9, 3） band in the b^3Пg （v=9） system in the region of 12065-12445 cm...The predissociation of the v=9 level in the b^3Пg state by the 3∑u^＋ state of helium eximer （He2） was studied based on the newly observed （9, 3） band in the b^3Пg （v=9） system in the region of 12065-12445 cm^-1 employing optical heterodyne-concentration modulation absorption spectroscopy. With the help of the previous potential energy curves and molecular constants of He2, the corresponding predissociation mechanism for the b^3Пg （v=9） state was analyzed. An RKR potential energy curve of b^3Пg and an ab initio potential curve of 3∑g^＋ were used to calculate the predissociation linewidths that show basic agreement with observations, which can quantitatively explain the experiments.展开更多
A kind of electric circuit is improved to optimize the linearity of edge filter demodulators in FBG .By using a logarithm amplifier and an extraction operation, the linear range of optimized edge filter demodulators h...A kind of electric circuit is improved to optimize the linearity of edge filter demodulators in FBG .By using a logarithm amplifier and an extraction operation, the linear range of optimized edge filter demodulators has been broadened effectively, and the requirement of optical filter＇s linear range has been reduced. Theoretical analyses and the simulation results indi-cated that the linear range of optimized edge fdter demodulator＇s covers the whole transition region of the edge filter, while a strict linearity of the optical filter is not necessary.展开更多
A discrimination measurement method and demodulation technique for fiber Bragg grating (FBG) sensors were presented using digital filtering technique. The system can control a tunable fiber Fabry-Perot filter with saw...A discrimination measurement method and demodulation technique for fiber Bragg grating (FBG) sensors were presented using digital filtering technique. The system can control a tunable fiber Fabry-Perot filter with sawtooth wave voltage generated by digital clock to interrogate FBG sensors. Using the analogue digital converter (ADC), the reflected FBG signals were sampled with synchronous digital clock. With the aid of digital matched filtering technique, the sampled FBG signals were processed to obtain the maximum signal-to-noise ratio (SNR) and the Bragg wavelength shift from the FBG signals was recovered. The results demonstrate that this system has a scanning range of 1 520 nm-1 575 nm,and the wavelength detection accuracy is less than 2 pm with 1.5 Hz scanning frequency.展开更多
基金Acknowledgments： This work is supported by the National Natural Science Foundation of China （No.11034002 and No.11004062）, the National Key Basic Research and Development Program of China （No.2010CB922903 and No.2011CB21602）, and the Basic Key Program of Shanghai Municipality （No.07JC14017）. Chuan-liang Li is grateful to the support of the PhD Program Scholarship Fund of the East China Normal University 2009. The authors thank Pro- fessor Robert J. LeRoy from University of Waterloo for providing his BCONT, RKR and LEVEL programs,and authors are also particularly grateful to Dr. Xing- can Dai from JI-LA and NIST for his helpful and useful suggestions and discussions in simulation.
文摘The predissociation of the v=9 level in the b^3Пg state by the 3∑u^＋ state of helium eximer （He2） was studied based on the newly observed （9, 3） band in the b^3Пg （v=9） system in the region of 12065-12445 cm^-1 employing optical heterodyne-concentration modulation absorption spectroscopy. With the help of the previous potential energy curves and molecular constants of He2, the corresponding predissociation mechanism for the b^3Пg （v=9） state was analyzed. An RKR potential energy curve of b^3Пg and an ab initio potential curve of 3∑g^＋ were used to calculate the predissociation linewidths that show basic agreement with observations, which can quantitatively explain the experiments.
文摘A kind of electric circuit is improved to optimize the linearity of edge filter demodulators in FBG .By using a logarithm amplifier and an extraction operation, the linear range of optimized edge filter demodulators has been broadened effectively, and the requirement of optical filter＇s linear range has been reduced. Theoretical analyses and the simulation results indi-cated that the linear range of optimized edge fdter demodulator＇s covers the whole transition region of the edge filter, while a strict linearity of the optical filter is not necessary.
基金Doctoral Foundation of Ministry of Education of China (No. 20040056008)
文摘A discrimination measurement method and demodulation technique for fiber Bragg grating (FBG) sensors were presented using digital filtering technique. The system can control a tunable fiber Fabry-Perot filter with sawtooth wave voltage generated by digital clock to interrogate FBG sensors. Using the analogue digital converter (ADC), the reflected FBG signals were sampled with synchronous digital clock. With the aid of digital matched filtering technique, the sampled FBG signals were processed to obtain the maximum signal-to-noise ratio (SNR) and the Bragg wavelength shift from the FBG signals was recovered. The results demonstrate that this system has a scanning range of 1 520 nm-1 575 nm,and the wavelength detection accuracy is less than 2 pm with 1.5 Hz scanning frequency.
