Multiplexed Active Optical Fiber Bragg Grating Sensor Array Enabled by Femtosecond Laser Induced Nanoscattering Centers

Optical fiber sensors (OFS) such as fiber Bragg gratings (FBGs) are passive and versatile sensor devices that have been used to perform a wide range of physical and chemical measurements. However, the performance and functionality of the OFS are limited by its passivity. This letter demonstrates an active fiber sensor scheme for multiparameter measurements. FBG-based optic fiber sensors are fabricated in an optical fiber core by femtosecond laser direct writing scheme. Guided light scattered out from laser-induced nanograting in fiber core is harnessed by on-fiber coating. Energy conversion films coated on the optical fiber convert scattered optical energy into thermal energy to heat the FBG sensor above ambient temperatures for active measurements. Functionalities of optically heated fiber sensor array are demonstrated for both temperature and liquid level measurements at the room temperatures.