Limits...
Interferometric fiber optic sensors.

Lee BH, Kim YH, Park KS, Eom JB, Kim MJ, Rho BS, Choi HY - Sensors (Basel) (2012)

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: School of Information and Communications, Gwangju Institute of Science and Technology, Buk-gu, Gwangju, Korea. leebh@gist.ac.kr

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.

No MeSH data available.


Related in: MedlinePlus

(a) Extrinsic FPI sensor made by forming an external air cavity, and (b) intrinsic FPI sensor formed by two reflecting components, R1 and R2, along a fiber.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3376629&req=5

f1-sensors-12-02467: (a) Extrinsic FPI sensor made by forming an external air cavity, and (b) intrinsic FPI sensor formed by two reflecting components, R1 and R2, along a fiber.

Mentions: A Fabry-Perot interferometer (FPI) is generally composed of two parallel reflecting surfaces separated by a certain distance [18]. Sometimes it is called an etalon [19]. Interference occurs due to the multiple superpositions of both reflected and transmitted beams at two parallel surfaces [20]. For the fiber optic cases, the FPI can be simply formed by intentionally building up reflectors inside or outside of fibers. FPI sensors can be largely classified into two categories: one is extrinsic and the other is intrinsic [21,22]. The extrinsic FPI sensor uses the reflections from an external cavity formed out of the interesting fiber [17]. Figure 1(a) shows an extrinsic FPI sensor, in which the air cavity is formed by a supporting structure. Since it can utilize high reflecting mirrors, the extrinsic structure is useful to obtain a high finesse interference signal [23]. Furthermore, the fabrication is relatively simple and does not need any high cost equipment. However, the extrinsic FPI sensors have disadvantages of low coupling efficiency, careful alignment, and packaging problem [19]. On the other hands, the intrinsic FPI fiber sensors have reflecting components within the fiber itself. For example, when the reflectors are formed within a fiber by any means, as in Figure 1(b), we can have the intrinsic FP interference. 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]. However, they still have a problem of using high cost fabrication equipment for the cavity formation. In other sense, when the cavity material is not the fiber itself, it is called extrinsic. However, the definition becomes vague due to the advent of specialty fibers and fiber devices.


Interferometric fiber optic sensors.

Lee BH, Kim YH, Park KS, Eom JB, Kim MJ, Rho BS, Choi HY - Sensors (Basel) (2012)

(a) Extrinsic FPI sensor made by forming an external air cavity, and (b) intrinsic FPI sensor formed by two reflecting components, R1 and R2, along a fiber.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3376629&req=5

f1-sensors-12-02467: (a) Extrinsic FPI sensor made by forming an external air cavity, and (b) intrinsic FPI sensor formed by two reflecting components, R1 and R2, along a fiber.
Mentions: A Fabry-Perot interferometer (FPI) is generally composed of two parallel reflecting surfaces separated by a certain distance [18]. Sometimes it is called an etalon [19]. Interference occurs due to the multiple superpositions of both reflected and transmitted beams at two parallel surfaces [20]. For the fiber optic cases, the FPI can be simply formed by intentionally building up reflectors inside or outside of fibers. FPI sensors can be largely classified into two categories: one is extrinsic and the other is intrinsic [21,22]. The extrinsic FPI sensor uses the reflections from an external cavity formed out of the interesting fiber [17]. Figure 1(a) shows an extrinsic FPI sensor, in which the air cavity is formed by a supporting structure. Since it can utilize high reflecting mirrors, the extrinsic structure is useful to obtain a high finesse interference signal [23]. Furthermore, the fabrication is relatively simple and does not need any high cost equipment. However, the extrinsic FPI sensors have disadvantages of low coupling efficiency, careful alignment, and packaging problem [19]. On the other hands, the intrinsic FPI fiber sensors have reflecting components within the fiber itself. For example, when the reflectors are formed within a fiber by any means, as in Figure 1(b), we can have the intrinsic FP interference. 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]. However, they still have a problem of using high cost fabrication equipment for the cavity formation. In other sense, when the cavity material is not the fiber itself, it is called extrinsic. However, the definition becomes vague due to the advent of specialty fibers and fiber devices.

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: School of Information and Communications, Gwangju Institute of Science and Technology, Buk-gu, Gwangju, Korea. leebh@gist.ac.kr

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.

No MeSH data available.


Related in: MedlinePlus