Functional potentialities and sensitivity of sensors made from multimode graded-index optical waveguides

It is shown that there are no fundamental limitations on the sensitivity, which might be associated with the wave nature of the radiation, of amplitude sensors made from multimode graded-index waveguides and the limitations found in practice are solely due to the fact that the optimal measurement procedure cannot be realized. The different sensitivities of modes in a graded-index waveguide to external perturbations make it possible to construct amplitude sensors with a tunable sensitivity. It is shown that, in principle, it is possible to increase exponentially the sensitivity of amplitude sensors by creating periodic longitudinal inhomogeneities in a graded-index waveguide and by using an active graded-index waveguide. A description is given of interference sensors made from multimode graded-index waveguides operating in conjunction with computer-synthesized spatial filters selecting the required superposition of modes. The sensitivity of such sensors is estimated.