  Present telescopes and future extremely large telescopes make use of
fiber-fed spectrographs to observe at optical and infrared wavelengths. The use
of fibers largely simplifies the interfacing of the spectrograph to the
telescope. At a high spectral resolution (R>50,000) the fibers can be used to
achieve very high spectral accuracy. GIANO is an infrared (0.95-2.5\mu m) high
resolution (R=50,000) spectrometer[1] [2] [3] that was recently commissioned at
the TNG telescope (La Palma). This instrument was designed and built for direct
feeding from the telescope [4]. However, due to constraints imposed on the
telescope interfacing during the pre-commissioning phase, it had to be
positioned on the rotating building, far from the telescope focus. Therefore, a
new interface to the telescope, based on IR-transmitting ZBLAN fibers with 85
\mu m core, was developed. In this article we report the first, preliminary
results of the effects of these fibers on the quality of the recorded spectra
with GIANO and with a similar spectrograph that we set-up in the laboratory.
The effects can be primarily associated to modal-noise (MN) that, in GIANO, is
much more evident than in optical spectrometers, because of the much longer
wavelengths.
