Critical sensitivity in hetero-modal interferometric sensor using spectral interrogation.

This paper reports on the finding of a critical working point in the sensitivity of hetero-modal interferometric optical sensors using spectral interrogation. At this point the theoretical sensitivity approaches infinity and the practical sensitivity will depend only on the measurement accuracy and noise sources present. If the critical condition is attained at a point of minimal power transfer, a phenomenon of splitting or bifurcation of the minimum dip is expected as sensing occurs. The conditions for attainment of these critical effects are discussed.