Title :
CO2-laser-induced long-period gratings in graded-index multimode fibers for sensor applications
Author :
Su, Lei ; Chiang, Kin Seng ; Lu, Chao
Author_Institution :
Network Technol. Res. Centre, Nanyang Technol. Univ., Singapore, Singapore
Abstract :
Long-period grating (LPG) fabricated in a graded-index multimode fiber (MMF) by deforming the geometry of the fiber periodically with a focused CO2-laser beam is reported. The effects of the grating parameters on the transmission of the grating are investigated. We show that the transmission characteristics of the grating are similar to those of an MMF subject to periodic microbending. Strong mode couplings take place in the grating when the pitch of the grating is equal to a specific value (∼1 mm), known as the critical spatial period of the fiber. The responses of some fabricated gratings to the axial strain and the change in the surrounding refractive index are measured and good sensitivities are achieved. Such MMF LPGs can be used potentially as physical and chemical sensors.
Keywords :
bending; diffraction gratings; fibre optic sensors; gradient index optics; laser beam effects; optical fibres; optical focusing; refractive index measurement; strain sensors; CO2; CO2 laser; axial strain; chemical sensors; fiber geometry deformation; focused CO2-laser beam; graded-index fibers; grating parameters; grating pitch; grating transmission; long-period gratings; multimode fibers; periodic microbending; physical sensors; refractive index; sensor applications; strong mode couplings; Capacitive sensors; Chemical sensors; Fiber gratings; Fiber lasers; Gas detectors; Laser beams; Optical fiber communication; Optical fiber devices; Optical fiber sensors; Refractive index; Chemical sensor; long-period grating (LPG); multimode fiber (MMF); strain sensor;
Journal_Title :
Photonics Technology Letters, IEEE
DOI :
10.1109/LPT.2005.861267
