The GraF instrument using a Fabry-Perot interferometer cross-dispersed with a grating was one of the first integral-field and long-slit spectrographs built for and used with an adaptive optics system. We describe its concept, design, optimal observational procedures and the measured performances. The instrument was used in 1997-2001 at the ESO 3.6 m telescope equipped with ADONIS adaptive optics and SHARPII+ camera. The operating spectral range was 1.2 - 2.5 microns. We used the spectral resolution from 500 to 10 000 combined with the angular resolution of 0.1 - 0.2. The quality of GraF data is illustrated by the integral field spectroscopy of the complex 0.9 x 0.9 central region of Eta Car in the 1.7 microns spectral range at the limit of spectral and angular resolutions.
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