Measuring the Radial Position of Defects within Optical Fibers Using Skew Rays

Abstract

Defects within optical fibers can cause premature failure in fiber-based systems and must be detected early to avoid performance degradation. Addressing this need can ensure that no defective optical fibers are being used by end users and improve processes to reduce the number of defects during manufacturing. The main challenge to date has been developing a technique that can measure defects along long lengths of fiber, within opaque packaging, and with position information. We demonstrate a simple and novel technique for detecting and radially resolving microscopic defects in packaged/buried fibers using an angle-resolved interrogator that analyzes the transmission of different ray groups. We have measured the accuracy to be as low as ±2 μm, which is sufficient for most fibers that have diameters in the order of ~100 μm.

Light-Sheet Skew-Ray Enhanced Pump-Absorption for Sensing

“…To elaborate, skew rays host larger numbers of reflections compared to that of meridional rays under the same θ, which can be a few orders of magnitude higher, as well as longer penetration lengths. This facilitates a longer total penetration path length inside a functional coating or an external medium (i.e., higher sensitivity to uniform external changes [20]- [22]), and a better circular coverage around the circumferential surface of the sensing fiber (i.e., higher probability of encountering point perturbations [23], and higher measurement-repeatability or better measurand averaging with non-uniform analytes) unless meridional rays are focused and centered. However, meridional rays pack larger portions of power in their evanescent fields due to smaller incident angles, which boosts the sensitivity.…”

Fiber-Optic Skew Ray Sensors

“…The combination of these two factors makes skew rays significantly more sensitive to surface imperfections than meridional rays". Through advanced signal processing [66], the upper radial position can be estimated to indicate whether the defect lies in the core, cladding or cladding-coating interface. This new technique allows for rapid characterization of buried optical fibers, which limit other methods from being practical.…”

Force Sensors Using the Skew-Ray-Probed Plastic Optical Fibers

“…The first three factors increase the chances of rays encountering localized physical perturbations that attenuate light. Thus, render skew rays are much more sensitive than meridional rays per unit fiber length, and are used for a variety of sensing applications [20]- [23] such as fiber defect detection [22]. The first (i.e., dominant), third and fourth factors are relevant to the proposed force sensors.…”