Long-period fiber gratings with overlay of variable refractive index

Transmission Characteristics of Long-Period Fiber Gratings Having Arbitrary Azimuthal/Radial Refractive Index Variations

A numerical method is presented for determining the transmittance of long-period (LP) fiber-gratings having arbitrary azimuthal/radial refractive index variations. The method uses coupled-mode theory and includes both the sine and cosine character of the LP modes. The model treats interactions between the fundamental mode and high-azimuthal-order cladding modes. The method utilizes the transfer...

Refractive index sensitivity of fibre optic long period gratings with SiO2 nanoparticle based mesoporous coatings

A fibre optic long period grating (LPG) with a nano-assembled mesoporous coating of alternate layers of poly (allylamine hydrochloride) (PAH) and SiO2 nanospheres was used for the development of a fibre-optic refractometer. PAH/SiO2 films of different thickness have been deposited onto LPG in order to study the effect of the film thickness on sensor performance. The device showed a sensitivity ...

Pressure Sensing in High-Refractive-Index Liquids Using Long-Period Gratings Nanocoated with Silicon Nitride

The paper presents a novel pressure sensor based on a silicon nitride (SiNx) nanocoated long-period grating (LPG). The high-temperature, radio-frequency plasma-enhanced chemical-vapor-deposited (RF PECVD) SiNx nanocoating was applied to tune the sensitivity of the LPG to the external refractive index. The technique allows for deposition of good quality, hard and wear-resistant nanofilms as requ...

Improved Refractive Index Sensitivity Utilizing Long-Period Gratings with Periodic Corrugations on Cladding

Towards refractive index sensitivity of long-period gratings at level of tens of µm per refractive index unit: fiber cladding etching and nano-coating deposition.

In this work we report experimental results on optimizing the refractive index (RI) sensitivity of long-period gratings (LPGs) by fiber cladding etching and thin aluminum oxide (Al2O3) overlay deposition. The presented LPG takes advantage of work in the dispersion turning point (DTP) regime as well as the mode transition (MT) effect for higher-order cladding modes (LP...