In the framework of the Enhancement Projects at JET, an extension of the capabilities of the Martin-Puplett interferometer has been required for the spectral analysis of the ECE perpendicular and oblique signals. That has been only possible with a complete redesign of the collection optics system. The new instrument is designed to analyze the incoming radiation from standard perpendicular view (two channels) and from oblique view of the ECE radiation at two different angles (four channels) at ~10o and ~22o from the major radius in the toroidal plane. The new optical scheme needed a totally new mechanical layout of the system. This work deals with the detailed description of the mechanical realization and the first characterization of the system.