Refractive index and concentration sensing of solutions using mechanically induced long period grating pair

Fiber grating sensors in medicine: Current and emerging applications

“…Since effective refractive index of a cladding mode and their coupling efficiency with the fundamental mode is dependent upon the refractive index of the surrounding medium, any change in the latter is easily detected using LPGs. This is the basic principle of an LPG based refractive index and concentration sensor [8][9][10].…”

“…where s are the electromagnetic field components of the two coupling modes and r and are radial and azimuthal co-ordinates respectively [10]. Obviously, any change in cladding field distribution will affect the coupling strength.…”

Long-period gratings in photonic crystal fibers for sensing of external refractive index change and macro-bending

“…6 They can also be used for online monitoring of concentration or refractive index change of of a chemical solution, especially for the hazardous liquid in harsh environment. 7 By directly measuring the bending curvature in situ, an LPG can also be employed in bending detection of smart structures, 8 seismic measurement, 9 and biomedical detection. 10 The principal characteristic of PCFs is the wavelength-scale air channels axially aligned in the cladding, which leads to a unique set of optical properties such as endlessly single-mode guidance, unusual dispersion properties, and high birefringence.…”

Optical Fiber Gratings in Perspective of Their Applications in Biomedicine

“…Where, s are the electromagnetic field components of the two coupling modes, r and Φ are radial and azimuthal co-ordinates respectively (Mishra et al 2005). Obviously, any change in cladding field distribution will affect the coupling strength.…”