Long-period fiber gratings written by arc discharge are heated at different temperatures, and the postheating changes of transmission characteristics are investigated. The resonance wavelengths are shifted to longer wavelengths by heating at a temperature lower than the fictive temperature of the fiber, and they move more quickly with increasing heating temperature. The resonance wavelength shifts more for the loss peak generated by the higher cladding mode. It is shown that the resonance wavelengths can be changed and adjusted up to 63-76 nm without significant degradation by the glass-structure change induced by heating.

Residual stress effects are examined by heating long-period gratings written in the fibers un-relaxed and relaxed the stress. It becomes evident that the trimming range of resonance wavelengths can be expanded by adjusting heating temperature.

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