Abstract
The long period fiber grating (LPFG) is widely used as a sensor due to its high sensitivity and resolution. However, the broad bandwidth of the attenuation bands formed by the mode coupling between the fundamental core mode and the cladding modes constitutes a difficulty when the device is used as a conventional sensor. To overcome this limitation, a Michelson interferometer-type sensor configuration has been developed, using an LPFG grating pair formed by coating a mirror at the distal end of the LPFG. This sensor configuration is more convenient to use and is able to overcome the limitations of the single LPFG based sensor as the shifts in the attenuation bands being more easily detectable due to the formation of the sharp spectral fringe pattern in the LPFG based Michelson interferometer. In this work, I studied the LPFG based Michelson interferometer as the refractive index sensor and discussed the sensitivity enhancement of the LPFG based Michelson interferometer as a refractive index sensor by employing higher order cladding modes and by reducing the cladding radius. The results demonstrated the HE17 mode with a cladding radius of 62.5 μm, in the range of surrounding refractive index (SRI) of 1–1.45, and its resonant peak showed a wavelength shift of 26.99 nm/RIU. When the cladding region was further reduced to 24 μm, the resonant peak showed a wavelength shift of 569.88 nm/RIU, resulting in a sensitivity enhancement of nearly 21 times. However, as the cladding region was etched further, then the HE17 order cladding mode and higher mode would be cut off. Therefore, the implementation of high sensitivity for SRI sensing with the reduced cladding in the LPFG based Michelson interferometer is dependent on the proper combination of the cladding radius and cladding mode order.
Article PDF
Similar content being viewed by others
Avoid common mistakes on your manuscript.
References
A. M. Vengsarkar, P. J. Lemaire, J. B. Judkins, V. Bhatia, T. Erdogan, and J. E. Sipe, “Long-period fiber gratings as band-rejection filters,” Journal of Lightwave Technology, 1996, 14(1): 58–65.
T. Erdogan, “Cladding-mode resonances in short- and long-period fiber grating filters,” Journal of the Optical Society of America A, 1997, 14(8): 1760–1773.
K. Shroeder, W. Ecke, R. Mueller, R. Willsch, and A. Andreev, “A fibre Bragg grating refractometer,” Measurement Science and Technology, 2001, 12(7): 757–764.
R. Slavik, J. Homola, J. Ctyroky, and E. Brynda, “Novel spectral fiber optic sensor based on surface plasmon resonance,” Sensors and Actuators B: Chemical, 2001, 74(1–3): 106–111.
Q. Huang, Y. Yu, Z. Ou, X. Chen, J. Wang, P. Yan, et al., “Refractive index and strain sensitivities of a long period fiber grating,” Photonic Sensors, 2014, 4(1): 92–96.
V. Bhatia, “Applications of long-period gratings to single and multi-parameter sensing,” Optics Express, 1999, 4(11): 457–466.
B. H. Lee and J. Nishii, “Notch filters based on cascaded multiple long-period fibre gratings,” Electronics Letters, 1998, 34(19): 1872–1873.
O. Duhem, J. F. Henninot, and M. Douay, “Study of in fiber Mach-Zehnder interferometer based on two spaced 3-dB long period gratings surrounded by a refractive index higher than that of silica,” Optics Communications, 2000, 180(4-6): 255–262.
L. Alwis, T. Sun, and K. T. V. Grattan, “Fibre optic long period grating-based humidity sensor probe using a Michelson interferometric arrangement,” Sensors and Actuators B: Chemical, 2013, 178: 694–699.
B. H. Lee and J. Nishii, “Self-interference of long-period fibre grating and its application as temperature sensor,” Electronics Letters, 1998, 34(21): 2059–2060.
P. L. Swart, “Long-period grating Michelson refractometric sensor,” Measurement Science and Technology, 2004, 15(8): 1576–1580.
A. V. Brakel, “Sensing characteristics of an optical fibre long-period grating Michelson refractometer,” Ph.D. dissertation, Rand Afrikaans University, Johannesburg, 2004.
M. G. Xu, R. Maaskant, M. M. Ohn, and A.T. Alavie, “Independent tuning of cascaded long period fibre gratings for spectral shaping,” Electronics Letters, 1997, 33(22): 1893–1894.
H. Chen and Z. Gu, “Characteristics of a long-period fiber grating with reduced cladding for refractive index sensing,” Journal of Modern Optics, 2011, 58(18): 1659–1665.
Author information
Authors and Affiliations
Corresponding author
Additional information
This article is published with open access at Springerlink.com
Rights and permissions
Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0), which permits use, duplication, adaptation, distribution, and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.
About this article
Cite this article
Singh, A. Long period fiber grating based refractive index sensor with enhanced sensitivity using Michelson interferometric arrangement. Photonic Sens 5, 172–179 (2015). https://doi.org/10.1007/s13320-015-0222-7
Received:
Revised:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s13320-015-0222-7