In the field of near infrared H2O sensing, the acquisition of the absorption signal usually is from a noisy background, thus it is important to adopt an effective signal demodulation method. This study introduced the ...In the field of near infrared H2O sensing, the acquisition of the absorption signal usually is from a noisy background, thus it is important to adopt an effective signal demodulation method. This study introduced the research progress in the field of trace water vapor detection, covering different individual gas detection techniques. On the basis of the conventional double-beam differential absorption, the division method in voltage and the dual-peak method based on the differential value of two adjacent absorption lines have been studied. Voltage division has an excellent stability to temperature variation, mechanical extrusion, and fiber bend loss. The dual-peak method proved a linear relation with the water vapor concentration, and this method provided a way to measure the concentration at high pressure. Furthermore, the so called balanced ratiometer detection （BRD） was introduced. It has an outstanding self-adjusting capability, and it can also avoid an excess phase difference caused by the current-to-voltage converting circuit, thus this method has a high sensitivity. In addition, the second harmonic technique applied to gas detection was introduced, and for the high-frequency modulation via driving current, l/f was suppressed apparently; as a result, this technique realized a better sensitive detection by one to two orders of magnitude.展开更多
A tunable modulation format converter based on spectral line-by-line pulse shaper is proposed to realize different format conversions.The pulse shaper works as a format converter by setting its frequency response equi...A tunable modulation format converter based on spectral line-by-line pulse shaper is proposed to realize different format conversions.The pulse shaper works as a format converter by setting its frequency response equivalent to the transform function between two formats.The working principles show that the format converter is suitable for different formats by adjusting its frequency response.Examples of format conversion from return to zero differential phase-shift keying(RZ-DPSK) to on-off keying(OOK) with different data packets and from return to zero(RZ) to non-return to zero(NRZ) are given.The results show that the format converter is not only suitable for different formats but also for random data packets.展开更多
基金This work was supported by the Natural Science Foundation of China （60977058 ＆ 61307101）, Independent Innovation Foundation of Shandong University （IIFSDU2012JC015）, the key technology projects of Shandong Province （2010GGX10137）, and promotive research fund for excellent young and middle-aged scientists of Shandong Province （BS2010DX028）.
文摘In the field of near infrared H2O sensing, the acquisition of the absorption signal usually is from a noisy background, thus it is important to adopt an effective signal demodulation method. This study introduced the research progress in the field of trace water vapor detection, covering different individual gas detection techniques. On the basis of the conventional double-beam differential absorption, the division method in voltage and the dual-peak method based on the differential value of two adjacent absorption lines have been studied. Voltage division has an excellent stability to temperature variation, mechanical extrusion, and fiber bend loss. The dual-peak method proved a linear relation with the water vapor concentration, and this method provided a way to measure the concentration at high pressure. Furthermore, the so called balanced ratiometer detection （BRD） was introduced. It has an outstanding self-adjusting capability, and it can also avoid an excess phase difference caused by the current-to-voltage converting circuit, thus this method has a high sensitivity. In addition, the second harmonic technique applied to gas detection was introduced, and for the high-frequency modulation via driving current, l/f was suppressed apparently; as a result, this technique realized a better sensitive detection by one to two orders of magnitude.
基金supported by the National Natural Science Foundation of China(No.61377075)New Century Excellent Talents in University(No.NCET-07-0611)
文摘A tunable modulation format converter based on spectral line-by-line pulse shaper is proposed to realize different format conversions.The pulse shaper works as a format converter by setting its frequency response equivalent to the transform function between two formats.The working principles show that the format converter is suitable for different formats by adjusting its frequency response.Examples of format conversion from return to zero differential phase-shift keying(RZ-DPSK) to on-off keying(OOK) with different data packets and from return to zero(RZ) to non-return to zero(NRZ) are given.The results show that the format converter is not only suitable for different formats but also for random data packets.
