Optical delay line intended to be implemented in an interferometer, comprising: - a polygon in rotation, - a first and a second reflector (21, 22), - a decoding splitter element, the decoding splitter element being arranged to receive a beam of light, called measurement beam, and for splitting this beam of light into a first light beam and a second light beam (Li1, Li2), - means arranged to direct the first light beam and the second light beam towards the polygon, characterized in that: - said polygon is arranged to modulate the respective optical paths of said first and second light beam (Li1, Li2), originating from the same measurement beam, and directed through said polygon respectively towards said first and second reflectors (21, 22), so as to generate an optical delay by difference between the optical paths of said first and second beams (Li1, Li2); said first and second beams (Li1, Li2) are: - respectively incident on a face of said polygon identical or different according to respectively a first angle of incidence (θ1) and a second angle of incidence (θ2), so that when one of the first or second angle of incidence (θ1, θ2) varies between a minimum value or zero and a maximum value, the other one of said first or second angle of incidence (θ1, θ2) varies between said maximum value and said minimum value or zero, and - arranged to be incident on the polygon along an axis passing though the centre of rotation of said polygon. - a polygon in rotation, - a first and a second reflector (21, 22), - a decoding splitter element, the decoding splitter element being arranged to receive a beam of light, called measurement beam, and for splitting this beam of light into a first light beam and a second light beam (Li1, Li2), - means arranged to direct the first light beam and the second light beam towards the polygon, characterized in that: - said polygon is arranged to modulate the respective optical paths of said first and second light beam (Li1, Li2), originating from the same measurement beam, and directed through said polygon respectively towards said first and second reflectors (21, 22), so as to generate an optical delay by difference between the optical paths of said first and second beams (Li1, Li2); said first and second beams (Li1, Li2) are: - respectively incident on a face of said polygon identical or different according to respectively a first angle of incidence (θ1) and a second angle of incidence (θ2), so that when one of the first or second angle of incidence (θ1, θ2) varies between a minimum value or zero and a maximum value, the other one of said first or second angle of incidence (θ1, θ2) varies between said maximum value and said minimum value or zero, and - arranged to be incident on the polygon along an axis passing though the centre of rotation of said polygon. - respectively incident on a face of said polygon identical or different according to respectively a first angle of incidence (θ1) and a second angle of incidence (θ2), so that when one of the first or second angle of incidence (θ1, θ2) varies between a minimum value or zero and a maximum value, the other one of said first or second angle of incidence (θ1, θ2) varies between said maximum value and said minimum value or zero, and - arranged to be incident on the polygon along an axis passing though the centre of rotation of said polygon.