The Charge eXchange Recombination Spectroscopy diagnostic system on the ITER plasma core (CXRS core) will provide spatially resolved measurements of plasma parameters. The optical front-end is located in upper port 3 and the light of 460 nm to 665 nm is routed to spectrometers housed in the tritium building. This paper describes the layout of the optical system in the port plug, cell and interspace areas. The layout is a continuation of the developments described in  and takes into account changes in the design of the upper port plug, considerations for the system lifetime as well as internal and external tolerances on the optical chain. The layout was selected also with a number of additional criteria, including optical performance, radiation shielding, maintainability and robustness. A free-space optical chain was added to relocate the coupling of the light into the optical fibres to the port cell. As a new sub-system, a line-of-sight finder based on the back-illumination and imaging of apertures at pupils and masks at images was added. With the line-of-sight finder, the absence of an object with detectable edges is addressed, enabling determination of deviations within the optical chain. Where feasible, existing solutions for sub-systems such as the shutter were adapted to the layout. The current status of the implementation is discussed.