SENSITIVITY ANALYSIS OF FIBER BRAGG GRATING SENSORS COATED BY METAL FILMS PRODUCED BY THE LASER-ASSISTED MASKLESS MICRODEPOSITION PROCESS

摘要

The sensitivity required for optical fiber sensors suchrnas fiber Bragg gratings (FBG) is highly dependent onrnapplications, environment of use and the magnitudernof physical parameters measured by the sensor. Inrnaddition, such sensitivity dependency is morerncomplicated if FBGs are embedded in metallicrnstructures using laser-assisted additivernmanufacturing. One of the methodologies for thernimprovement of the sensitivity of FBGs is to coatrnthem with thin films. The coating not only protectsrnthe optical fiber sensors but also improves theirrnsensitivity. In this paper, we propose a combinedrncoating process for on-fiber thin film depositionrnusing Laser Assisted Maskless Microdepositionrn(LAMM) followed by electroless Ni plating. Anrnanalyticalumerical model is also developed to studyrnthe effect of coating thickness on the sensorrnsensitivity. In addition, the role of laser parameters onrnthe coating characteristics such as appearance qualityrnand compositions is experimentally investigated.