In an optical waveguide grating in an optical fiber having a cladding region around a core region, a periodic refractive index distribution is existed in a predetermined area of the core region along the optical axis. The core region has a composition of GeO2—P2O5—SiO2 based glass, for example, whereas the cladding region is made of SiO2, and the co-doping ratio in the core region is adjusted, so as to lower the temperature dependence of characteristics. The doping amount of P2O5 in the core region is preferably {fraction (1/15)} to 1 times, more preferably 0.6 to 1 times that of GeO2.