  NIRPS (Near Infra-Red Planet Searcher) is an AO-assisted and fiber-fed
spectrograph for high precision radial velocity measurements that will operate
in the YJH-bands. While using an AO system in such instrument is generally
considered to feed a single-mode fiber, NIRPS is following a different path by
using a small multi-mode fiber (more specifically called "few-mode fiber").
This choice offers an excellent trade-off by allowing to design a compact
cryogenic spectrograph, while maintaining a high coupling efficiency under bad
seeing conditions and for faint stars. The main drawback resides in a much more
important modal-noise, a problem that has to be tackled for allowing 1m/s
precision radial velocity measurements. We study the impact of using an AO
system to couple light into few-mode fibers. We focus on two aspects: the
coupling efficiency into few-mode fibers and the question of modal noise and
scrambling. We show first that NIRPS can reach coupling >= 50% up to magnitude
I=12, and offer a gain of 1-2 magnitudes over a single-mode solution. We
finally show that the best strategy to mitigate modal noise with the AO system
is among the simplest: a continuous tip-tilt scanning of the fiber core.
