  CRIRES, the ESO high resolution infrared spectrometer, is a unique instrument
which allows astronomers to access a parameter space which up to now was
largely uncharted. In its current setup, it consists of a single-order
spectrograph providing long-slit, single-order spectroscopy with resolving
power up to R=100,000 over a quite narrow spectral range. This has resulted in
sub-optimal efficiency and use of telescope time for all the scientific
programs requiring broad spectral coverage of compact objects (e.g. chemical
abundances of stars and intergalactic medium, search and characterization of
extra-solar planets). To overcome these limitations, a consortium was set-up
for upgrading CRIRES to a cross-dispersed spectrometer, called CRIRES+. This
paper presents the updated optical design of the crossdispersion module for
CRIRES+. This new module can be mounted in place of the current pre-disperser
unit. The new system yields a factor of >10 increase in simultaneous spectral
coverage and maintains a quite long slit (10"), ideal for observations of
extended sources and for precise sky-background subtraction.
