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: This work fabricated an elliptical hollow-core photonic bandgap fiber by controlling lateral tension in the hollow core region during the fiber drawing process and experimentally measured the strain and temperature sensitivities of the fabricated EC-PBGF-based Sagnac loop interferometer.
Abstract: We fabricated an elliptical hollow-core photonic bandgap fiber (EC-PBGF) by controlling lateral tension in the hollow core region during the fiber drawing process. The absolute value of group modal birefringence becomes relatively high near the bandgap boundaries. We also experimentally measured the strain and temperature sensitivities of the fabricated EC-PBGF-based Sagnac loop interferometer. The strain and temperature sensitivities were very much dependent upon the wavelength. Moreover this PBGF-based interferometer can be a good sensor of physical parameters such as strain and temperature.
74 citations
TL;DR: In this paper, a fiber-optic flow velocity sensor based on a twin-core fiber Michelson interferometer has been proposed and demonstrated, which is a segment of twin core fiber acting as cylinder cantilever beam.
Abstract: A novel fiber-optic flow velocity sensor based on a twin-core fiber Michelson interferometer has been proposed and demonstrated. The sensor only is a segment of twin-core fiber acting as cylinder cantilever beam. The force exerted on the cylinder by the slow flow speeds of order mm/s of the fluid with unknown velocity bends the fiber, which corresponds to the shift of the phase of the twin-core in-fiber integrated Michelson interferometer.
72 citations
"Interferometric Fiber Optic Sensors..." refers methods in this paper
...There has been another MI application for measuring flow velocity [68]....
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TL;DR: In this article, an in-fiber Mach-Zehnder interferometer (MZI) was fabricated and characterized for solution refractive index (RI) sensors, which consists of two cascade double cladding fibers in a standard single mode fiber (SMF).
Abstract: An in-fiber Mach-Zehnder interferometer (MZI) was fabricated and characterized for solution refractive index (RI) sensors. The MZI consists of two cascade double cladding fibers (DCFs) in a standard single mode fiber (SMF). The DCFs serve as the in-fiber couplers which split and combine light propagating in the core and the outer cladding region. Since the cladding mode is excited, the interference spectrum is sensitive to the ambient RI variation. Within the RI range from 1.3333 to 1.4535, the sensor characteristics were characterized. The sensitivity of 31 nm/RIU and 823 nm/RIU were obtained for the lower RI (1.34) and the higher RI (1.44), respectively. With the mass-producing of DCF and the easy fabrication process of the sensor head, the proposed in-fiber MZI is a potential alternative for the RI sensor application.
71 citations
"Interferometric Fiber Optic Sensors..." refers methods in this paper
...Beside theses, there have been MZIs using a double cladding fiber [57], micro-cavities [58], and a twin-core fiber [59]....
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TL;DR: In this paper, a fiber-optic Fabry-Perot sensing structure based on the utilization of a suspended-core fiber is presented, which is formed when a small length of the suspended core fiber is spliced to the end of a standard single-mode fiber.
Abstract: A fiber-optic Fabry-Perot sensing structure based on the utilization of a suspended-core fiber is presented. The interferometric structure is formed when a small length of the suspended-core fiber is spliced to the end of a standard single-mode fiber. The interfering waves are generated by the refractive-index mismatches between the two fibers in the splice region and at the end of the suspended-core fiber. Thermal and strain responses of two different sensing heads associated with suspended-core fibers with three and four holes are characterized.
67 citations
TL;DR: An all-fiber interferometer fabricated with a single piece of an endless single-mode photonic crystal fiber by an electric arc discharge is presented and strain sensing is experimentally demonstrated.
Abstract: We present an all-fiber interferometer fabricated with a single piece of an endless single-mode photonic crystal fiber (PCF) by an electric arc discharge. By forming a long period grating (LPG) at a point and collapsing the air holes at another point along the PCF, the simple but effective interferometer could be implemented. The LPG made a strong wavelength selective mode coupling between the core and cladding modes in the interesting wavelength range, while the air-hole collapse induced wavelength independent mode couplings. By cascading them, we could implement the all-fiber interferometer. As a potential application of the proposed all PCF interferometer, strain sensing is experimentally demonstrated.
63 citations
"Interferometric Fiber Optic Sensors..." refers methods in this paper
...By combining the LPG method and the collapsing method, the insertion loss could be reduced by ~3 dB [52]....
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