25 August 2008 Simultaneously sensing multiple gases using a single length of hollow-core photonic bandgap fiber with sub-minute response times
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A sensing configuration based on commercially available hollow-core photonic bandgap (PBG) fiber for the simultaneous optical detection of multiple gas samples is presented. Spectroscopic sensors based on microstructured fiber technology have been of recent interest. However, most designs have limited sensor response times due to long gas diffusion filling times for fiber lengths >1 m. Sensor response times that are shorter in duration unlike diffusion-limited filling times are reported. A length of PBG fiber with a 12.5 micron core diameter, an optical spectrum analyzer and a broadband light source were employed to operate in the transmission region where the absorption lines for sample gases, including acetylene and carbon dioxide, correspond to the near-IR region. A gas-filling time of 1 minute 30 seconds for acetylene to completely fill a ~2 meter length of PBG fiber at a pressure < 15 Psi was demonstrated. Reduced filling times that approach the sub-minute regime are possible, leading to shorter sensor response times. The sensitivity of the proposed system is also reported. Using the techniques presented, the detection of concentrations < 100 ppm for acetylene gas at pressures < 15 Psi is possible. The relatively low-loss PBG guidance mechanism (< 0.1 dB/m) confines light to the gas-filled region promoting long optical-field-interaction lengths (> 1 m) with small sample volumes (~μL) resulting in a compact, bend-insensitive rugged device with gas detecting sensitivities that have the potential to be higher than capillary based detectors.
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R. M. Wynne, R. M. Wynne, K. Creedon, K. Creedon, B. Barabadi, B. Barabadi, S. Vedururu, S. Vedururu, J. Merritt, J. Merritt, A. Ortega, A. Ortega, "Simultaneously sensing multiple gases using a single length of hollow-core photonic bandgap fiber with sub-minute response times", Proc. SPIE 7056, Photonic Fiber and Crystal Devices: Advances in Materials and Innovations in Device Applications II, 70560W (25 August 2008); doi: 10.1117/12.794226; https://doi.org/10.1117/12.794226

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