Compositional dependence of the temperature sensitivity in long-period fiber gratings with doping concentration of <math display='inline' overflow='scroll'><msub><mi>GeO</mi><mrow><mn>2</mn></mrow></msub></math> and <math display='inline' overflow='scroll'><msub><mstyle mathvariant='normal'><mtext>B</mtext></mstyle><mrow><mn>2</mn></mrow></msub><msub><mstyle mathvariant='normal'><mtext>O</mtext></mstyle><mrow><mn>3</mn></mrow></msub></math> and their applications

The systematic analysis of the relationship between temperature sensitivity of long-period fiber gratings and the doping concentrations of GeO 2 and B 2 O 3 in the core and cladding regions, depending on their structure ofthe refractive index profile, is investigated. Based on this analysis, the temperature sensitivities of fiber gratings are suppressed and enhanced to 0.002 and -0.44 nm/&#176;C, respectively. We also discuss the versatile applications of long-period fiber gratings to gain-flattening filters of optical amplifiers and strain/temperature sensors, corresponding to their temperature sensitivity. The theoretical and experimental results are very useful for the design of optical communication devices and mechanical sensors based on long-period fiber gratings.