Simple and Prospective Refractive Index Sensor involving Trapezoidal Index Profiles in the context of Splice Loss Analysis and Identification of appropriate profile

Department of Electronic Science, University of Calcutta, 92 Acharya Prafulla Chandra Road, Kolkata 700009, India

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Published online: 29 May 2026

Abstract

In this paper, we investigate, extensively, the effect of aspect ratio on the splice loss due to certain longitudinal misalignment at the joint between two single mode trapezoidal index fibers of identical aspect ratio. From this study, we report that as the value of aspect ratio decreases from 1.0 to 0.0, the splice loss increases, considerably, and, hence, triangular index fiber exhibits maximum loss. Further, the effect of refractive index of the index matching fluid filling the gap between two identical single mode triangular index fibers in reducing the splice loss is investigated and simple empirical relation for refractive index in terms of splice loss is prescribed to predict the refractive index of a medium from the direct knowledge of splice loss. Thus, we propose a method to study the prospective and possible use of the loss-sensitive triangular index profile as a refractive index sensor based on our empirical relation. We also show that even if there is a little digression from triangular index profile during fabrication, the system users can still confidently apply and use our empirical relation. The physical significance of our results is justified from basic diffraction ideas. Also, our refractometric formulation involving single mode fiber is simpler than the deeply involved relations of the recently proposed longitudinally displaced refractometer based on multimode fibers.