  We present the final reduction and calibration of the FIRBACK ISOPHOT data.
FIRBACK is a deep cosmological survey performed at 170 microns. This paper
deals with the ISOPHOT C200 camera with the C160 filter. We review the whole
data reduction process and compare our final calibration with DIRBE (for the
extended emission) and IRAS (for point sources). The FIRBACK source extraction
and galaxy counts is discussed in a companion paper (Dole et al., 2001).
