In this paper,a long period grating(LPG) written in a photonic crystal fiber(PCF) was investigated.By selecting an appropriate grating period,a LPG with approximate zero temperature sensitivity was realized.By utilizing the properties of the LPG in the PCF,two kinds of optical fiber sensors were developed.The first one was a low-cost temperature-insensitive strain sensor,in which the LPG served as a temperature insensitive strain sensing head.When a distributed feedback(DFB) laser at 1 553 nm was used as th...