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vel se with eous ature e de ature 70, 0 sors in measuring strain, temperature, and other physical quantities by detecting the shift in the Bragg wavelength. But, in general, the Bragg wavelength shift in a FBG comes from two effects, i.e., strain and strain and temperature with a single FBG and an erbium-doped fiber ~EDF! amplifier ~EDFA!. The amplified spontaneous emission ~ASE! power of an EDFA varies almost linearly with temperaturetemperature, and hence, when only the wavelength shift is measured, the effects of both parameters are hardly distinguishable. Many works to discrimi-nate these parameters have been carried out,3,4 among which are the approaches for which hybrid FBGylong-period grating5 ~LPG! and a single LPG are used.6 The hybrid FBGyLPG sensor consists of two FBG’s and an LPG in which the mode-coupling wavelength of the LPG lies between the Bragg wave-lengths of the FBG’s. The strain and the tempera-ture are determined by the different responses of the FBG and the LPG to the two parameters. However, in this sensor scheme the temperature-sensing range within a considerable range.7 By virtue of this char-acteristic, we measure temperature within relative intensity noise. We perform the strain measure-ment by monitoring the transmission dip shift of the FBG and subtracting the temperature effect from it. 2. Simultaneous Measurement of Both Strai