An optical module for use in a motion responsive system includes a support and a proof mass mechanically coupled and displaceable relative to the support along at least one sensing axis in response to a motion experienced by the support. The module also includes an optical monitoring assembly for monitoring the proof mass with an optical beam impinging on the proof mass, the beam including a plurality of dedicated spectral components. The module further includes an optical spectral filter including a plurality of filtering regions, each being associated with a corresponding dedicated spectral component and having a spectral profile including a distinct dedicated filtering band encompassing the spectral component, such that a displacement of the proof mass along the at least one sensing axis produces, after filtering of the beam, a change in optical power of the spectral components indicative of the motion experienced by the support.