Ultrasensitive strain sensor based on Vernier- effect improved parallel structured fiber-optic Fabry-Perot interferometer

Ferreira

Bierlich

et al. 2019

Sensors

113

The optical Vernier effect provides magnification of the sensing capabilities of an interferometer, allowing unprecedented sensitivities and resolutions to be achieved. Just like a calliper uses two different scales to achieve higher resolution measurements, the optical Vernier effect is based on the overlap between the responses of two interferometers with slightly detuned interference signals. Here we present in detail, as a novel approach, the generation of optical harmonics of the Vernier effect with Fabry-Perot interferometers, where the two interferometers can have very different frequencies in the interferometric pattern. We demonstrate not only a considerable enhancement, but also a better control of the sensitivity magnification factor, which scales up with the order of the harmonics, breaking the limits of the conventional Vernier effect as used today. In addition, this novel concept opens also new ways of dimensioning the sensing structures, together with improved fabrication tolerances.

Section: Experimental Demonstrationsupporting

confidence: 87%

Section: Fundamental Optical Vernier Effectmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Optical Harmonic Vernier Effect: A New Tool for High Performance Interferometric Fiber Sensors

Ferreira

Bierlich

et al. 2019

Sensors

113

“…1 a), the Vernier effect is generated in a parallel configuration, by means of a 3 dB fibre coupler 4 . It can be seen as a specific Michelson interferometer, however since the connecting parts are approximately invariant this approach for analysis of the parallel Vernier structure has not been used in literature 3 , 4 , 9 , 11 – 14 . The structure is illuminated with a supercontinuum source, and the reflected spectral response is measured with an optical spectrum analyser.…”

Section: Resultsmentioning

confidence: 99%

“…Recently, the use of the Vernier effect has found great interest in interferometric sensing concepts, and especially in fibre Fabry-Perot elements, as a tool to considerably increase their sensitivity [1][2][3][4] . This concept is based on the beating signal of two slightly detuned interferometers (one sensing interferometer and one reference interferometer) [5][6][7] .…”

Section: Giant Refractometric Sensitivity By Combining Extreme Opticamentioning

confidence: 99%

Giant refractometric sensitivity by combining extreme optical Vernier effect and modal interference

Kobelke

Bierlich

et al. 2020

Sci Rep

The optical Vernier effect consists of overlapping responses of a sensing and a reference interferometer with slightly shifted interferometric frequencies. The beating modulation thus generated presents high magnified sensitivity and resolution compared to the sensing interferometer, if the two interferometers are slightly out of tune with each other. However, the outcome of such a condition is a large beating modulation, immeasurable by conventional detection systems due to practical limitations of the usable spectral range. We propose a method to surpass this limitation by using a few-mode sensing interferometer instead of a single-mode one. The overlap response of the different modes produces a measurable envelope, whilst preserving an extremely high magnification factor, an order of magnification higher than current state-of-the-art performances. Furthermore, we demonstrate the application of that method in the development of a giant sensitivity fibre refractometer with a sensitivity of around 500 µm/RIU (refractive index unit) and with a magnification factor over 850.

Optical Vernier Effect: Recent Advances and Developments

Laser & Photonics Reviews

Bartelt

Frazão

2021

168

The optical analog of the Vernier effect applied to fiber interferometers is a recent tool to enhance the sensitivity and resolution of optical fiber sensors. This effect relies on the overlap between the signals of two interferometers with slightly detuned interference frequencies. The Vernier envelope modulation generated at the output spectrum presents magnified sensing capabilities (i.e., magnified wavelength shift) compared to that of the individual sensing interferometers that constitute the system, leading to a new generation of highly sensitive fiber sensing devices. This review analyses the recent advances and developments of the optical Vernier effect from a fiber sensing point-of-view. Initially, the fundamentals of the effect are introduced, followed by an extensive review on the state-of-the-art, presenting all the different configurations and types of fiber sensing interferometers used to introduce the optical Vernier effect. This paper also includes an overview of the complex case of enhanced Vernier effect and the introduction of harmonics to the effect.