Review of Turn around Point Long Period Fiber Gratings

Gambhir, Monika; Gupta, Shilpi

doi:10.4236/jst.2015.54009

Cited by 14 publications

(5 citation statements)

References 39 publications

(25 reference statements)

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“…DTP-LPGs offer two resonance minima shifting towards opposite directions with RI increase. The DTP working conditions can be fine-tuned by etching the cladding [11]. DTP-LPGs are the most sensitive to RI changes, which makes them suitable for biosensing applications [12,13].…”

Section: Introductionmentioning

confidence: 99%

Long-Period Gratings and Microcavity In-Line Mach Zehnder Interferometers as Highly Sensitive Optical Fiber Platforms for Bacteria Sensing

Eftimov

Janik

Koba

et al. 2020

Sensors

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Selected optical fiber sensors offer extraordinary sensitivity to changes in external refractive (RI), which make them promising for label-free biosensing. In this work the most sensitive ones, namely long-period gratings working at (DTP-LPG) and micro-cavity in-line Mach-Zehnder interferometers (µIMZI) are discussed for application in bacteria sensing. We describe their working principles and RI sensitivity when operating in water environments, which is as high as 20,000 nm/RIU (Refractive index unit) for DTP-LPGs and 27,000 nm/RIU for µIMZIs. Special attention is paid to the methods to enhance the sensitivity by etching and nano-coatings. While the DTP-LPGs offer a greater interaction length and sensitivity to changes taking place at their surface, the µIMZIs are best suited for investigations of sub-nanoliter and picoliter volumes. The capabilities of both the platforms for bacteria sensing are presented and compared for strains of Escherichia coli, lipopolysaccharide E. coli, outer membrane proteins of E. coli, and Staphylococcus aureus. While DTP-LPGs have been more explored for bacteria detection in 102–106 Colony Forming Unit (CFU)/mL for S. aureus and 103–109 CFU/mL for E. coli, the µIMZIs reached 102–108 CFU/mL for E. coli and have a potential for becoming picoliter bacteria sensors.

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Section: Introductionmentioning

confidence: 99%

Long-Period Gratings and Microcavity In-Line Mach Zehnder Interferometers as Highly Sensitive Optical Fiber Platforms for Bacteria Sensing

Eftimov

Janik

Koba

et al. 2020

Sensors

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“…They are intrinsically sensitive to external perturbations, enabling the measurement of several parameters [ 7 ]. The fabrication of an LPFG with high sensitivity to the external perturbations is possible by selecting a cladding mode and period at, or very close to, the turning around point (TAP) [ 8 , 9 , 10 , 11 , 12 , 13 ].…”

Section: Introductionmentioning

confidence: 99%

“…Several methods have been explored for the fabrication of LPFGs, including exposure to UV and CO 2 laser radiation [ 14 , 15 , 16 , 17 ], electric arc discharge [ 18 , 19 ], and mechanical pressure [ 1 ]. However, post-processing techniques such as taper tuning [ 10 ], cladding etching [ 20 ], and overlay coating [ 10 , 11 ] are necessary for the fabrication and tuning of an LPFG at the TAP. These fabrication processes can weaken the optical fiber and render its implementation difficult [ 1 ].…”

Section: Introductionmentioning

confidence: 99%

Temperature Stability and Spectral Tuning of Long Period Fiber Gratings Fabricated by Femtosecond Laser Direct Writing

Viveiros

Almeida

Coelho

et al. 2020

Sensors

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Long period fiber gratings (LPFGs) were fabricated in a standard single mode fiber (SMF-28e) through femtosecond (fs) laser direct writing. LPFGs with longer and shorter periods were fabricated, which allows coupling from the fundamental core mode to lower and higher order asymmetric cladding modes (LP1,6 and LP1,12, respectively). For the grating periods of 182.7 and 192.5 µm, it was verified that the LP1,12 mode exhibits a TAP at approximately 1380 and 1448 nm in air and water, respectively. Characterization of the LPFGs subjected to high-temperature thermal treatment was accomplished. Fine-tuning of the resonance band’s position and thermal stability up to 600 °C was shown. The temperature sensitivity was characterized for the gratings with different periods and for different temperature ranges. A maximum sensitivity of −180.73, and 179.29 pm/°C was obtained for the two resonances of the 182.7 µm TAP LPFG, in the range between 250 and 600 °C.

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“…This chapter aims to provide a more comprehensive coverage of LPGs which operate at and around the phase matching turning point, with respect to what can be found in existing literature [22]. The typical characteristics and fabrication considerations will be discussed.…”

Section: Introductionmentioning

confidence: 99%

Optical Fibre Long-Period Grating Sensors Operating at and around the Phase Matching Turning Point

Wong¹,

Juan²,

Ibsen³

et al. 2019

Applications of Optical Fibers for Sensing

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Optical fibres have been exploited as sensors for many years and they provide a versatile platform with a small form factor. Long-period gratings (LPGs) operating at and around the phase matching turning point (PMTP) possess some of the highest sensitivities to external perturbations in the family of LPG-based sensor devices. This type of optical fibre grating has been demonstrated as a sensor for use in a wide range of applications. In this review chapter, an overview of PMTP LPGs is presented and the key developments, findings and applications are highlighted. The fabrication considerations and sensor limitations are also discussed.

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Review of Turn around Point Long Period Fiber Gratings

Cited by 14 publications

References 39 publications

Long-Period Gratings and Microcavity In-Line Mach Zehnder Interferometers as Highly Sensitive Optical Fiber Platforms for Bacteria Sensing

Long-Period Gratings and Microcavity In-Line Mach Zehnder Interferometers as Highly Sensitive Optical Fiber Platforms for Bacteria Sensing

Temperature Stability and Spectral Tuning of Long Period Fiber Gratings Fabricated by Femtosecond Laser Direct Writing

Optical Fibre Long-Period Grating Sensors Operating at and around the Phase Matching Turning Point

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