Interferometric Fiber Optic Sensors
23 Feb 2012-Sensors (Multidisciplinary Digital Publishing Institute (MDPI))-Vol. 12, Iss: 3, pp 2467-2486
TL;DR: Each type of interferometric sensor is reviewed in terms of operating principles, fabrication methods, and application fields and some specific examples of recently reported interferometeric sensor technologies are presented in detail to show their large potential in practical applications.
Abstract: Fiber optic interferometers to sense various physical parameters including temperature, strain, pressure, and refractive index have been widely investigated. They can be categorized into four types: Fabry-Perot, Mach-Zehnder, Michelson, and Sagnac. In this paper, each type of interferometric sensor is reviewed in terms of operating principles, fabrication methods, and application fields. Some specific examples of recently reported interferometeric sensor technologies are presented in detail to show their large potential in practical applications. Some of the simple to fabricate but exceedingly effective Fabry-Perot interferometers, implemented in both extrinsic and intrinsic structures, are discussed. Also, a wide variety of Mach-Zehnder and Michelson interferometric sensors based on photonic crystal fibers are introduced along with their remarkable sensing performances. Finally, the simultaneous multi-parameter sensing capability of a pair of long period fiber grating (LPG) is presented in two types of structures; one is the Mach-Zehnder interferometer formed in a double cladding fiber and the other is the highly sensitive Sagnac interferometer cascaded with an LPG pair.
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TL;DR: Recent research and applications in structural health monitoring of composite aircraft structures using FOS have been critically reviewed, considering both the multi-point and distributed sensing techniques.
Abstract: In-service structural health monitoring of composite aircraft structures plays a key role in the assessment of their performance and integrity. In recent years, Fibre Optic Sensors (FOS) have proved to be a potentially excellent technique for real-time in-situ monitoring of these structures due to their numerous advantages, such as immunity to electromagnetic interference, small size, light weight, durability, and high bandwidth, which allows a great number of sensors to operate in the same system, and the possibility to be integrated within the material. However, more effort is still needed to bring the technology to a fully mature readiness level. In this paper, recent research and applications in structural health monitoring of composite aircraft structures using FOS have been critically reviewed, considering both the multi-point and distributed sensing techniques.
461 citations
Cites background or methods from "Interferometric Fiber Optic Sensors..."
...Sensors based on the Mach-Zender, and Michelson interferometers, also using long period gratings (LPGs) and photonic crystal fibres (PCFs) [14,15], have been used preferably for refractive index [16], temperature [17] or velocity measurement [18], while the Sagnac interferometer has been applied mainly to rotation measurements [19]....
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...The operation of interferometric sensors [14] is based on the change of the optical phase difference between two light waves with the same frequency, caused by the variation of a physical quantity....
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TL;DR: A wide variety of FPI sensors are reviewed in terms of fabrication methods, principle of operation and their sensing applications in a study on interferometric optical fiber sensors.
Abstract: Optical fibers have been involved in the area of sensing applications for more than four decades. Moreover, interferometric optical fiber sensors have attracted broad interest for their prospective applications in sensing temperature, refractive index, strain measurement, pressure, acoustic wave, vibration, magnetic field, and voltage. During this time, numerous types of interferometers have been developed such as Fabry-Perot, Michelson, Mach-Zehnder, Sagnac Fiber, and Common-path interferometers. Fabry-Perot interferometer (FPI) fiber-optic sensors have been extensively investigated for their exceedingly effective, simple fabrication as well as low cost aspects. In this study, a wide variety of FPI sensors are reviewed in terms of fabrication methods, principle of operation and their sensing applications. The chronology of the development of FPI sensors and their implementation in various applications are discussed.
291 citations
Cites background from "Interferometric Fiber Optic Sensors..."
...To the extent of the authors‘ knowledge, there are a few review articles that have partly talked about the common fabrication, sensing technologies and measurands of Fabry-Perot Interferometric fiber-optic sensors, including [44], which only covers microcavities that play a significant role in forming FPI, vibration sensing in [45], strain measurement in [46], acousto-ultrasonic sensing in [47], and also includes a number of recent reviews given in [48] where the recent trends of FPI fabrication, methods and application are presented....
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TL;DR: In this paper, the authors focus on optical refractive index (RI) sensors with no fluorescent labeling required, and utilize two parameters to characterize and compare the performance of optical RI sensors: sensitivity to RI change (denoted by symbol SRI) and figure of merit (in short, FoM).
Abstract: DOI: 10.1002/adom.201801433 Scientific American selects plasmonic sensing as the top 10 emerging technologies of 2018.[15] Almost every single new plasmonic or photonic structure would be explored to test its sensing ability.[16–29] These works tend to report the sensing performance of their own structure. Some declare that their sensitivity breaks the world record. However, there is still a missing literature on what the world record really is, the gap between the experiments and the theoretical limit, as well as the differences between metal-based plasmonic sensors and dielectric-based photonic sensors. To push plasmonic and photonic sensors into industrial applications, an optical sensing technology map is absolutely necessary. This review aims to cover a wide range of most representative plasmonic and photonic sensors, and place them into a single map. The sensor performances of different structures will be distinctly illustrated. Future researchers could plot the sensing ability of their new sensors into this technology map and gauge their performances in this field. In this review, we focus on optical refractive index (RI) sensors with no fluorescent labeling required. We will utilize two parameters to characterize and compare the performance of optical RI sensors: sensitivity to RI change (denoted by symbol SRI) and figure of merit (in short, FoM). For simplicity, we restrict our discussions to bulk RI change, where the change in RI occurs within the whole sample. There is another case where the RI variation occurs only within a very small volume close to the sensor surface. This surface RI sensitivity is proportional to the bulk RI sensitivity, the ratio of the thickness of the layer within which the surface RI variation occurs, and the penetration depth of the optical mode.[6] The bulk RI sensitivity defines the ratio of the change in sensor output (e.g., resonance angle, intensity, or resonant wavelength) to the bulk RI variations. Here, we limit our discussions to the spectral interrogations and the bulk RI sensitivity SRI is given by[3,5–7,30]
259 citations
TL;DR: An overview of the different types of FOS used for strain/temperature sensing in composite materials and their compatibility with and suitability for embedding inside a composite material is presented.
Abstract: This paper provides an overview of the different types of fiber optic sensors (FOS) that can be used with composite materials and also their compatibility with and suitability for embedding inside a composite material. An overview of the different types of FOS used for strain/temperature sensing in composite materials is presented. Recent trends, and future challenges for FOS technology for condition monitoring in smart composite materials are also discussed. This comprehensive review provides essential information for the smart materials industry in selecting of appropriate types of FOS in accordance with end-user requirements.
252 citations
Cites background from "Interferometric Fiber Optic Sensors..."
...A Fabry-Perot interferometer (FPI) generally comprises of two parallel reflecting surfaces separated by a certain distance [66]....
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...It is possible to tune the intensity of the interferometric modes of an EFPI sensor by varying the gap between the two reflecting surfaces [66]....
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...Interferometric fiber sensors [66] can also be employed for strain/temperature measurements in composite materials and this is discussed in detail in this section....
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...The reflection or transmission spectrum of an FPI is a wavelength dependent intensity modulation of the input light spectrum, resulting from the optical phase difference between the reflected and transmitted beams [66,67]....
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...The optical phase difference between reflected or transmitted beams at a particular wavelength of the FPI is basically specified as [66]:...
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TL;DR: In this article, the optical fiber sensors employed in environmental monitoring are summarized for understanding of their sensing principles and fabrication processes, followed by discussion on the potentials of OFS in manufacturing.
Abstract: Environmental monitoring has become essential in order to deal with environmental resources efficiently and safely in the realm of green technology. Environmental monitoring sensors are required for detection of environmental changes in industrial facilities under harsh conditions, (e.g. underground or subsea pipelines) in both the temporal and spatial domains. The utilization of optical fiber sensors is a promising scheme for environmental monitoring of this kind, owing to advantages including resistance to electromagnetic interference, durability under extreme temperatures and pressures, high transmission rate, light weight, small size, and flexibility. In this paper, the optical fiber sensors employed in environmental monitoring are summarized for understanding of their sensing principles and fabrication processes. Numerous specific applications in petroleum engineering, civil engineering, and agricultural engineering are explored, followed by discussion on the potentials of OFS in manufacturing.
236 citations
References
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TL;DR: The all-PCF Mach-Zehnder interferometer was formed by mechanically inducing two identical long-period fiber gratings (LPGs) in the PCF by mechanically induced two identicalLong-period Fiber gratings in thePCF to investigate the spectral properties of a LPG and a LGas pair.
Abstract: We demonstrate implementation of an all-fiber Mach–Zehnder interferometer formed in a photonic crystal fiber (PCF). We formed the all-PCF Mach–Zehnder interferometer by mechanically inducing two identical long-period fiber gratings (LPGs) in the PCF. The spectral properties of a LPG and a LPG pair were investigated. The interference fringe formed within the stop band of the LPG pair varied with the period and the strength of the gratings, and the fringe spacing was decreased with increasing grating separation. From the fringe spacing measurement the differential effective group index of the PCF was calculated to be Δm≈2.8×10-3.
170 citations
"Interferometric Fiber Optic Sensors..." refers background in this paper
...Even with the photonic crystal fiber (PCFs) made of a single material, pure silica, a pair of LPGs could be made by applying periodic pressure along the PCF [44]....
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TL;DR: A cross-talk free simultaneous measurement system for temperature and external refractive index (ERI) implemented by dual-cavity Fabry-Perot (FP) fiber interferometer demonstrated, which showed that temperature could be determined independently from the spatial frequency shift without being affected by the ERI.
Abstract: We propose and demonstrate a cross-talk free simultaneous measurement system for temperature and external refractive index (ERI) implemented by dual-cavity Fabry-Perot (FP) fiber interferometer. The sensing probe consists of two cascaded FP cavities formed with a short piece of multimode fiber (MMF) and a micro-air-gap made of hollow core fiber (HOF). The fabricated sensor head was ultra-compact; the total length of the sensing part was less than 600 mum. Since the reflection spectrum of the composite FP structures is given by the superposition of each cavity spectrum, the spectrum measured in the wavelength domain was analyzed in the Fourier or spatial frequency domain. The experimental results showed that temperature could be determined independently from the spatial frequency shift without being affected by the ERI, while the ERI could be also measured solely by monitoring the intensity variation in the spatial frequency spectrum. The ERI and the temperature sensitivities were approximately 16 dB/RIU for the 1.33-1.45 index range, and 8.9 nm/ degrees C at low temperature and 14.6 nm/ degrees C at high temperature, respectively. In addition, it is also demonstrated that the proposed dual-cavity FP sensor has potential for compensating any power fluctuation that might happen in the input light source.
167 citations
"Interferometric Fiber Optic Sensors..." refers background or methods in this paper
...The RI of the liquid solution calculated from the intensity variation of the Fourier peak is plotted in Figure 5(b) [38]....
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...Figure 7(d) shows one method in which a short piece of MMF is fusion spliced into a SMF at two points along the SMF....
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...The reflection spectrum of the double cavity FPI sensor, implemented with a piece of HOF of a length of ~70 μm and a MMF of ~360 μm, is shown in Figure 4(b)....
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...Since the HOF cavity and the MMF cavity have different thermo-optic coefficients, the temperature-induced movement of the first peak is different from the movements of the other peaks [37]....
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...By adjusting the lengths of multiple MMF cavities, multiplexing several sensors is also possible....
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TL;DR: In this article, an all-fiber high-resolution refractive index sensor based on a microstructured fiber Bragg grating is presented, which relies on a partial and localized etching of the cladding layer along a standard grating.
Abstract: In this work, an all-fiber high-resolution refractive index sensor based on a microstructured fiber Bragg grating is presented. The proposed structure relies on a partial and localized etching of the cladding layer along a standard grating. The main spectral changes of the structured grating are the increasing of the stopband and the formation of a narrow allowed band strongly dependent on the etching features and the surrounding refractive index. A sensor prototype has been fabricated by using wet etching and a proper masking procedure; experimental results reveal the possibility to carry out low-cost refractive index measurements with a resolution of 4/spl middot/10/sup -5/.
126 citations
TL;DR: In this paper, an anisotropic microstructure was introduced into the cross section of a photonic crystal fiber (HB-PCF) by enlarging the size of air holes of one row.
Abstract: We report on enhanced torsion sensitivity by using a highly birefringent photonic crystal fiber (HB-PCF)-based Sagnac interferometer. In order to increase the torsion sensitivity, we introduced an anisotropic microstructure into the cross section of an HB-PCF by enlarging the size of air holes of one row. This can result in a high birefringence of the order of 10-3 and low sensitivities to bending and temperature. The torsion sensitivity was measured to be high with ~0.06 nm/°.
120 citations
TL;DR: In this article, the sensing head is formed by a long-period fiber grating combined with a high-birefringence fiber loop mirror, resulting in a configuration capable of temperature and strain discrimination.
Abstract: This work presents an alternative solution for simultaneous measurement of strain and temperature. The sensing head is formed by a long-period fiber grating combined with a high-birefringence fiber loop mirror resulting in a configuration capable of temperature and strain discrimination. These optical devices have opposite sensitivity responses when a variation of temperature and/or strain is applied. Maximum errors of plusmn0.8degC and plusmn21muepsiv are reported over 60 degC and 700-muepsiv measurement ranges, respectively
117 citations