We demonstrate a novel device consisting of two concatenated chirped long period fiber gratings (LPG) that exhibit
multiple pass bands. Transmission spectra of single and dual chirped LPG were simulated theoretically and
investigated experimentally show a qualitatively good match. The dual chirped LPGs with multiple pass bands in the
transmission spectrum could find applications as WDM channel isolation filter.
We demonstrate the use of a pair of mechanically induced long period gratings (LPGs) for sensing the refractive index and concentration of liquids for which NaCl solutions of different concentrations and standard refractive index liquids are studied. The effect of varying the refractive index and/or concentration is reflected in changing output power loss values at resonance wavelengths. For a concentration change from 5 to 20 g per 100 ml, the maximum variation detected in optical output power is 20 pW, while for a refractive index variation from 1.446 to 1.458, it is 11 pW. These studies are quite useful for chemical, pharmaceutical, biological, and process control sensing applications.
An application of mechanically created long-period fiber gratings as sensitive bend sensors in structures and other areas is suggested. A resonance splitting of about 10 nm is observed under a maximum bend curvature of 0.4 m–1, producing a bend sensitivity of 25 nm/m–1. The design features of the experimental setup developed for the realization of mechanically created long-period fiber gratings and measurement of their output spectrum under different bend curvatures are discussed.