  The GREGOR Fabry-Perot Interferometer (GFPI) is one of three first-light
instruments of the German 1.5-meter GREGOR solar telescope at the Observatorio
del Teide, Tenerife, Spain. The GFPI allows fast narrow-band imaging and
post-factum image restoration. The retrieved physical parameters will be a
fundamental building block for understanding the dynamic Sun and its magnetic
field at spatial scales down to 50 km on the solar surface. The GFPI is a
tunable dual-etalon system in a collimated mounting. It is designed for
spectropolarimetric observations over the wavelength range from 530-860 nm with
a theoretical spectral resolution of R ~ 250,000. The GFPI is equipped with a
full-Stokes polarimeter. Large-format, high-cadence CCD detectors with powerful
computer hard- and software enable the scanning of spectral lines in time spans
equivalent to the evolution time of solar features. The field-of-view of 50" x
38" covers a significant fraction of the typical area of active regions. We
present the main characteristics of the GFPI including advanced and automated
calibration and observing procedures. We discuss improvements in the optical
design of the instrument and show first observational results. Finally, we lay
out first concrete ideas for the integration of a second FPI, the Blue Imaging
Solar Spectrometer, which will explore the blue spectral region below 530 nm.
