The back propagation method is applied to GPS occultation measurements of the lower stratosphere in order to reduce diffraction effects and to enhance the vertical resolution of the derived temperature profiles. The ionospheric bending angle correction should not be applied to small-scale bending angle fluctuations (λz < 1 km) of the GPS L1 and L2 signal, otherwise the retrieved profiles have enhanced artificial noise. Temperature profiles of two occultation events near to Japan on 4 and 5 February 1997 are discussed as examples for two different states of the lower stratosphere. One time the small-scale fluctuations appear as sinusoidal wave trains. The other time the high-resolution temperature profile has stairs which may result from atmospheric wave energy dissipation within a turbulence layer at each stair. The spectral energy distribution of the retrieved temperature fluctuations of both examples are well explained by the theoretical power spectra of saturated gravity waves at vertical wavelengths 0.1--2 km.