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.
Citations
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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: Two novel schemes for refractometry based on a long-period fiber grating- (LPG-) based Michelson interferometer are presented, designed to overcome the measurement dependence of previously demonstrated LPG-basedRefractometry on the immersion depth.
Abstract: We present two novel schemes for refractometry based on a long-period fiber grating– (LPG-) based Michelson interferometer These schemes are designed to overcome the measurement dependence of previously demonstrated LPG-based refractometry on the immersion depth The first utilizes an unshielded LPG and the second, a shielded one Both schemes were tested over a certain refractive-index range, and the measurement of glucose concentration in water was experimentally demonstrated In addition, the temperature sensitivity of the two schemes is discussed
100 citations
"Interferometric Fiber Optic Sensors..." refers background in this paper
...by coating the LPG with metal, which prevented the exposure to liquid [64]....
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TL;DR: The thermo-optic coefficient of the core material of a fiber is analyzed by use of a pair of long-period fiber gratings and is calculated by repetition of the measurement at different temperatures.
Abstract: The thermo-optic coefficient of the core material of a fiber is analyzed by use of a pair of long-period fiber gratings. First the effective index difference between the core and the cladding modes is measured from the peaks of the interference fringe generated by the grating pair. The order of the cladding mode is decided by the cutoff wavelength and the numerical aperture of the fiber. The material index of the fiber core is obtained in terms of wavelength. At each wavelength the index is chosen to minimize the difference between the measured and the calculated spectra of the grating pair. Finally the thermo-optic coefficient of the fiber core is calculated by repetition of the measurement at different temperatures. With a germanosilicate-core fiber and a boron codoped germanosilicate-core fiber, the thermo-optic coefficients were 1.1x10(-5)/( degrees )C and 0.75x10(-5)/( degrees )C, respectively.
99 citations
"Interferometric Fiber Optic Sensors..." refers methods in this paper
...An MZI temperature sensor using LPGs has been presented [45], where the thermo-optic coefficient of the fiber core material was analyzed by using a pair of LPGs....
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TL;DR: In this article, a Fabry-Perot (F-P) interferometric sensor based on hollow-core photonic bandgap fiber where the strain is gauged by measuring the spectrum shift of the reflected optical signal is presented.
Abstract: We design and demonstrate a miniature all-fiber Fabry-Perot (F-P) interferometric sensor based on hollow-core photonic bandgap fiber where the strain is gauged by measuring the spectrum shift of the reflected optical signal. The F-P cavity in the order of millimeters is fabricated by simple techniques of cleaving and fusion splicing. The sensitivity of the sensor is 1.55 pm/muepsiv at the wavelength of 1550 nm and the contrast of the intensity reaches 4-6 dB. Temperature and bend insensitivity and excellent repeatability of the sensor make it convenient for a wide range of applications.
96 citations
"Interferometric Fiber Optic Sensors..." refers background in this paper
...Especially the strain sensing ability at specific external disturbing conditions could be successfully demonstrated with MOFs [41,42]....
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...The environmental stability of MOFs is better than that of conventional SMFs....
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...Intrinsic cavities have been implemented by many types of specialty optical fiber devices such as micro-structured optical fibers (MOFs) or FBGs [40–43]....
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TL;DR: In this article, a temperature-insensitive fiber optic sensor for high-resolution measure of refractive index is proposed and demonstrated, based on Fresnel reflection modulated by Fabry-Perot interference, which consists of a section of singlemode fiber (SMF) tip coated with a thin film of SU-8 at the end of the fiber tip.
Abstract: A temperature-insensitive fiber optic sensor for high-resolution measure of refractive index is proposed and demonstrated. The sensor is based on Fresnel reflection modulated by Fabry-Perot interference, which consists of a section of single-mode fiber (SMF) tip coated with a thin film of SU-8 at the end of the fiber tip. The fringe contrast of the interference spectrum reflected from the sensor head is used to determine the extern RI. The experimental results agree well with the theoretical results and show that the fringe contrast is not sensitive to temperature variation. Such a refractive index sensor can offer the refractive index resolution and accuracy of 5 × 10-6 and 5 × 10-5, respectively. By simultaneous tracking the wavelength shift of the interference pattern, the sensor also has the potential capability for the simultaneous measurement of liquid RI and temperature.
95 citations
"Interferometric Fiber Optic Sensors..." refers background in this paper
...The local cavity of the intrinsic FPI can be formed by a lot of methods such as micro machining [24–27], fiber Bragg gratings (FBGs) [28,29], chemical etching [30,31], and thin film deposition [32,33]....
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TL;DR: In this paper, a cleaved optical fiber is immersed in hydrofluoric acid and the compositional variation within the core and the cladding results in the core region being etched at a faster rate.
Abstract: When a cleaved optical fibre is immersed in hydrofluoric acid, the compositional variation within the core and the cladding results in the core-region being etched at a faster rate. This paper presents details of the experimental procedures that were used to etch SM 800 optical fibres and the characterization of the micro-cavities using a 3D surface profiler, optical and scanning electron microscopy. Two such acid-etched fibres were fusion spliced to create an intrinsic Fabry–Perot cavity. These strain sensors were surface-mounted on to fibre reinforced composite test specimens and subjected to quasi-static and cyclic loading. The intrinsic fibre Fabry–Perot sensors were interrogated using low-coherence interferometry. The output from the intrinsic Fabry–Perot sensors showed excellent correlation with surface-mounted electrical resistance strain gauges during quasi-static and cyclic loading.
89 citations
"Interferometric Fiber Optic Sensors..." refers background in this paper
...The local cavity of the intrinsic FPI can be formed by a lot of methods such as micro machining [24–27], fiber Bragg gratings (FBGs) [28,29], chemical etching [30,31], and thin film deposition [32,33]....
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