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Given the increasing demands for quality assurance in the food industry, a significant challenge emerges in the form of expensive integration of food sensors into packaging. This integration is crucial for strengthening food safety measures and ensuring the impeccable quality of food products. Official laboratory food safety testing heavily relies on expensive and bulky equipment. This article presents a new chemical sensing platform and a comparative study of in-house built novel designs for a robust multimode chemical sensor head probed by highly sensitive light-sheet skew rays for addressing cost and footprint issues. The sensing mechanism is the interaction between evanescent field mediated by refined skew rays propagating through a structured coreless multimode fiber and external chemicals, resulting in probe light absorption. The sensitivity is enhanced by the controlled excitation of skew rays using a light sheet and four specially engineered coreless multimode fiber structure, including uniform, tapered, microstub and microbubble designs. The sensitivity was demonstrated to be as high as 0.046 (dB/cm) / dB(1 ng/ml) and the limit of detection as low as 1.028 ng/ml for the microbubble structure. The results of our research pave the groundwork for a new range of chemical sensors suitable for food safety monitoring.

Abstract: Spatial reuse of optical frequencies has been shown to be possible through a novel spatial domain multiplexing (SDM) technique that uses spatial multiplexer at the input end to launch multiple channels of the same wavelength inside a single strand of carrier fiber and then employs spatial filtering methods to de-multiplex the different optical channels at the output end. The individual SDM channels are confined to dedicated spatial locations inside the fiber while traversing through it owing to helical propagation of light. This presents attenuation and dispersion models of such a system. Experimentally obtained beam profile and resultant crosstalk of two such spatially multiplexed co-propagating SDM channels of the same wavelength over standard step index multimode optical fibers are also presented. [ABSTRACT FROM AUTHOR]

This paper reports a novel launch scheme for coupling light into the skew rays of a graded index fiber. This is accomplished by utilizing a diffractive optical element in conjunction with a single mode fiber to mode match a graded index fiber. Results are used to confirm the fact that the element does improve the coupling into the skew rays of graded index fiber. This approach offers an alternative to existing methods based on tilting and angular offsets for the conditioned launch problem [ABSTRACT FROM PUBLISHER]