A long period grating-based chemical sensor insensitive to the influence of interfering parameters.

An optical fibre chemical sensor that is insensitive to interfering parameters including temperature and surrounding refractive index is described. The sensor is based upon a Mach-Zehnder interferometer formed by a pair of identical cascaded long period gratings (LPGs), with the entire device coated with a mesoporous coating of silica nanoparticles. A functional material is infused only into the coating over the section of optical fibre separating the LPGs. The transmission spectrum of the device consists of a channeled spectrum arising from interference of the core and cladding modes within the envelope of the LPG resonance band. Parameters such as temperature, strain and surrounding refractive perturb the entire device, causing the phase of the channeled spectrum and the central wavelength of the envelope shift at the same rate. Exposure of the device to the analyte of interest perturbs only the optical characteristics of the section of fibre into which the functional material was infused, thus influencing only the phase of the channeled spectrum. Measurement of the phase of the channeled spectrum relative to the central wavelength of the envelope allows the monitoring of the concentration of the analyte with no interference from other parameters.

[1]  A. Vengsarkar,et al.  Optical fiber long-period grating sensors. , 1996, Optics letters.

[2]  B. Lee,et al.  Bending sensitivity of in-series long-period fiber gratings. , 1998, Optics letters.

[3]  Ian Bennion,et al.  Phase shifted and cascaded long-period fiber gratings , 1999 .

[4]  S. James,et al.  Optical fibre long-period grating sensors: characteristics and application , 2003 .

[5]  Thomas K. Gaylord,et al.  Transmission characteristics of long-period fiber gratings having arbitrary azimuthal/radial refractive index variations , 2003 .

[6]  Imran Ishaq,et al.  Cascaded long-period gratings with nanostructured coatings. , 2005, Optics letters.

[7]  Ping Miao,et al.  Sensitivity characteristics of long-period fiber gratings , 2005, SPIE/OSA/IEEE Asia Communications and Photonics.

[8]  Ralph P. Tatam,et al.  Response of fiber-optic long-period gratings operating near the phase-matching turning point to the deposition of nanostructured coatings , 2008 .

[9]  B.H. Lee,et al.  Simultaneous Measurement of Temperature and Strain Based on Double Cladding Fiber Interferometer Assisted by Fiber Grating Pair , 2008, IEEE Photonics Technology Letters.

[10]  Ralph P. Tatam,et al.  Optical fibre long period grating based selective vapour sensing of volatile organic compounds , 2010 .

[11]  Sergiy Korposh,et al.  Fiber optic long period grating sensors with a nanoassembled mesoporous film of SiO2 nanoparticles. , 2010, Optics express.

[12]  Ralph P. Tatam,et al.  Optical fibre long period grating with a nanoporous coating formed from silica nanoparticles for ammonia sensing in water , 2012 .

[13]  Ralph P. Tatam,et al.  Pronounced aromatic carboxylic acid detection using a layer-by-layer mesoporous coating on optical fibre long period grating , 2012 .

[14]  Stavros Pissadakis,et al.  An ethanol vapor detection probe based on a ZnO nanorod coated optical fiber long period grating. , 2012, Optics express.

[15]  S. W. James,et al.  Properties of Length-Apodized Phase-Shifted LPGs Operating at the Phase Matching Turning Point , 2012, Journal of Lightwave Technology.