title: Capturing reflected cladding modes from a fiber Bragg grating with a double-clad fiber coupler.
abstract: We present a novel measurement scheme using a double-clad fiber coupler (DCFC) and a fiber Bragg grating (FBG) to resolve cladding modes. Direct measurement of the optical spectra and power in the cladding modes is obtained through the use of a specially designed DCFC spliced to a highly reflective FBG written into slightly etched standard photosensitive single mode fiber to match the inner cladding diameter of the DCFC. The DCFC is made by tapering and fusing two double-clad fibers (DCF) together. The device is capable of capturing backward propagating low and high order cladding modes simply and efficiently. Also, we demonstrate the capability of such a device to measure the surrounding refractive index (SRI) with an extremely high sensitivity of 69.769 ± 0.035 μW/RIU and a resolution of 1.433 × 10(-5) ± 8 × 10(-9) RIU between 1.37 and 1.45 RIU. The device provides a large SRI operating range from 1.30 to 1.45 RIU with sufficient discrimination for all individual captured cladding modes. The proposed scheme can be adapted to many different types of bend, temperature, refractive index and other evanescent wave based sensors.
authors.affiliation: Department of Electrical Engineering, École Polytechnique de Montréal, C.P. 6079, Succ. Centre-ville, Montréal H3C 3A7, QC, Canada. mohamad-diaa.baiad@polymtl.ca
authors.forename: Mohamad Diaa
authors.initials: MD
authors.lastname: Baiad
authors.forename: Mathieu
authors.initials: M
authors.lastname: Gagné
authors.forename: Simon
authors.initials: S
authors.lastname: Lemire-Renaud
authors.forename: Etienne
authors.initials: E
authors.lastname: De Montigny
authors.forename: Wendy-Julie
authors.initials: WJ
authors.lastname: Madore
authors.forename: Nicolas
authors.initials: N
authors.lastname: Godbout
authors.forename: Caroline
authors.initials: C
authors.lastname: Boudoux
authors.forename: Raman
authors.initials: R
authors.lastname: Kashyap
mesh_terms: D004867:Equipment Design; D019544:Equipment Failure Analysis / Q000295:instrumentation* / Q000379:methods*; D005336:Fiber Optic Technology / Q000295:instrumentation*; D007909:Lenses; D012031:Refractometry / Q000295:instrumentation* / Q000379:methods*