Choice of step and near step profiles from splice loss analysis of trapezoidal index single mode fibers leading to a proposal of a longitudinal displacement sensor

Abstract

In this paper, an in-depth investigation is carried out on the effect of aspect ratio on splice loss between a pair of identical single mode trapezoidal index fibers in the presence of longitudinal and transverse misalignments. Splice loss is, interestingly, observed to get reduced, with the increase of aspect ratio and becomes minimum for unit aspect ratio for step profiles. Also, it is nearing minimum for near-step profiles. So, if there exists a little imperfection, say about ten percent, from step index profile, there will be no significant increase in the loss than that in step profile. This extended loss-tolerant feature in the step and near-step region revalidates the choice of the available step profile, technically used in communication. Thus, even for a digression in fabrication, system users should feel confident to use it. The physical significance of the results is justified from basic diffraction ideas. Finally, the entire study leads to a novel proposal of a longitudinal displacement sensor through simple and straight-forward empirical formulation to estimate the longitudinal misalignment from the knowledge of the splice loss of widely available step index fiber simply with air in the gap.