Abstract: An optical filtering device (1) comprising: a ring resonator (2); and a multimode interference coupler (3) comprising two inputs (4, 7), two outputs (5, 8) and a multimode waveguide (9) connecting the two inputs to the two outputs, the coupler having a first input (4) serving as an input for the filtering device and able to receive an input optical signal (10), and a first output (5) corresponding to the output of the filtering device and able to produce an output optical signal (12), the ring resonator (2) being arranged so as to connect a second output (8) of the coupler to a second input (7) of the coupler, wherein the filtering device comprises a tuning element (6) able to modify locally the refractive index in the coupling zone (11) of said multimode waveguide (9) in order to vary a coupling coefficient between the coupler (3) and the ring resonator (2).