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Abstract
This study investigates the effect of bending radius on signal attenuation in single-mode and multimode optical fibers to support the future development of microRNA (miRNA) biosensors for Crocodylus porosus detection in Sarawak. Experiments were conducted at 1310 nm, 1490 nm, and 1550 nm wavelengths with bending radii from 0.5 cm to 2.0 cm. Single-mode fibers showed high bending sensitivity, with maximum loss reaching 65.12 dB at 1550 nm and 0.5 cm radius. Multimode fibers showed minimal loss. These results provide baseline data for designing U-shaped fiber biosensors for species-specific miRNA detection.
Keywords: Optical fiber, Bending loss, Single-mode fiber, Multimode fiber, miRNA biosensor, Crocodylus porosus
1 Introduction
Human-crocodile conflicts in Sarawak have increased, with 164 attacks reported between 2000 and 2020, mainly involving Crocodylus porosus [1,2]. Early detection of the species is important for public safety and conservation.
MicroRNA (miRNA)-based detection offers species-specific monitoring [3]. C. porosus has 644 known miRNAs, with 78% unique to crocodilians [4]. Although eDNA is commonly used for aquatic monitoring, environmental factors often affect its accuracy [5].
Optical fiber biosensors, especially U-shaped designs, are promising for miRNA detection due to their high sensitivity [6]. However, bending causes signal loss, known as bending loss, influenced by fiber type, radius, and wavelength [7,8]. This study evaluates bending loss in single-mode and multimode fibers across three wavelengths to guide future sensor development for C. porosus detection.
2 Materials and Methods
Single-mode and multimode optical fibers were tested at 1310 nm, 1490 nm, and 1550 nm across bending radii from 0.5 cm to 2.0 cm.
Fibers were connected using fusion splicing (Signal Fire AI-6C Fusion Splicer) to ensure low-loss signal paths. Optical power was measured using an FLS-1013 Light Source and an FPM-3010+ Optical Power Meter. Baseline power was recorded with the fiber straight, followed by measurements at each bending radius.
Bend loss was calculated by comparing pre- and post-bend power. Results are reported in decibels (dB). U-shaped fibers were formed using a stainless steel straw as a mold, fixed using heat from a Bunsen burner, and inspected before measurement.
3 Results and Discussion
3.1 Single-Mode Fibers
Single-mode fibers showed high bending sensitivity. Maximum loss was 65.12 dB at 1550 nm with a 0.5 cm radius. Loss decreased with larger radii and shorter wavelengths. This aligns with known macrobending loss theory [7,8].
3.2 Multimode Fibers
Multimode fibers showed minimal loss, below 0.1 dB across all conditions. Small fluctuations were likely due to instrument sensitivity.
3.3 Comparison
Single-mode fibers are more sensitive to bending, making them better for biosensing applications. Multimode fibers offer higher signal stability but lower sensitivity.
4 Conclusion
Single-mode fibers, especially at 1550 nm, demonstrated high bending sensitivity suitable for future miRNA biosensing targeting C. porosus. Multimode fibers showed stable transmission with minimal loss. This study provides baseline data for designing U-shaped fiber sensors. Future work will focus on fiber surface functionalization using APTES and AuNPs to enhance detection sensitivity.
References
[1] Hassan, R., Gani, M.I.Z.A. Crocodiles in western of Sarawak, Malaysia. In: RCSTSS 2014, Springer, Singapore (2013)
[2] Gani, M.I.Z.A., et al. Human-Crocodile Conflicts in Sarawak. Int. J. Biol. Biomed. Eng., 16, 186–195 (2022)
[3] Bartel, D.P. Metazoan MicroRNAs. Cell, 173(1), 20–51 (2018)
[4] Ghosh, A., et al. Identification of MicroRNAs in C. porosus. Anal. Chim. Acta, 1100, 1–10 (2020)
[5] Zhao, B., et al. Bacterial abundance and eDNA degradation. Front. Environ. Sci., 11, (2023)
[6] Wen, H.-Y., et al. U-Shaped Fiber Biosensor for miRNA. Sensors, 20(5), 1509 (2020)
[7] Wang, P., et al. Macrobending Losses in Single Mode Fiber. Microw. Opt. Technol. Lett., 49(9), 2133–2138 (2007)
[8] Roy, P., Khan, H. R. Bending and Microbending Losses. IOSR J. Appl. Phys., 15(2), 50–54 (2023)
