Towards high sensitivity gas detection with hollow-core photonic bandgap fibers

Abstract

This paper investigates the effect of modal interference on the performance of hollow-core photonic bandgap fiber (HC-PBF) gas sensors. By optimizing mode launch, using proper length of sensing HC-PBF, and applying proper wavelength modulation in combination with lock-in detection, as well as appropriate digital signal processing, an estimated lower detection limit of less than 1 part-per-million by volume (ppmv) acetylene is achieved.

In-fiber modal interferometer for high sensitivity gas detection

“…The average spacing between adjacent interference fringe peaks, as shown in Fig. 2, is calculated to be ~70 pm, which is consistent with the beating between fundamental core mode and cladding modes for a 30-cm-long HC-PBF [3]. The slow-varying envelope, as seen in Fig.…”

“…The signal-to-noise ratio (SNR) is calculated to be ~405 and the lower detection limit for a SNR of unity can then be estimated to be ~2 ppm (~710 -5 in terms of NEA). This result is ~22 times better than state-of-theart HC-PBF gas sensors based on direct absorption [3]. This simple sensor configuration would allow compact novel gas sensors to be built along a single optical fiber cable.…”

“…However, the lower detection limits of HC-PBF gas sensors reported so far are found limited by modal interference (MI) effect because the current commercial HC-PBFs support higher order core/cladding modes [2]. By optimizing mode launch, using proper length of sensing HC-PBF, applying proper wavelength modulation in combination with lock-in detection, and using appropriate digital signal processing after signal-detection, an acetylene sensor with a detection limit of less than 1 ppm was demonstrated with a 13-meter-long HC-PBF [3]. We also demonstrated significant reduction of MI in HC-PBF by fusion splicing HC-PBF to standard single mode fiber (SMF) with proper fusion parameters to collapse the cladding holes of HC-PBF.…”

Dielectric-Grating-Coupled Surface Plasmon Resonance From the Back Side of the Metal Film for Ultrasensitive Sensing

“…In recent years, fiber optical sensor technology has been developed for sensing of vibration [7], strain [8], gas [9], [10], and bio-molecules [11]. Integration of various nanostructures with optical fibers represents a new sensor architecture to overcome those limitations suffered by conventional optical sensor technologies and is promising to result in flexible and portable sensor tips for on-site and real-time sensing.…”

Hollow-core photonic bandgap fiber gas sensor with high sensitivity and fast response

“…Instead of fusion splicing, a 13 m HC-1550-02 sample is mechanically spliced to SMFs at both ends, with a gap between the ends of the SMF and HC-PBF. The gaps serves as channels for gas filling/evacuation and the size of the gaps is selected for optimal mode launch, as discussed in [13]. The two connection joints were enclosed respectively in two compact gas chambers, one of which was connected to a high pressure gas cylinder containing 982 ppm acetylene while the other was left open to atmosphere.…”