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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) Transmission spectra of an LPG pair under temperature variations; the spectrum was shifted with the same phase; (b) The amount of the spectrum shift with temperature; it was shifted toward longer wavelength with the sensitivity of ∼39 pm/°C; (c) The spectra under strain variations; only the phase was changed without affecting the envelop curve; (d) The amount of the phase shift measured with strain [48].
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f8-sensors-12-02467: (a) Transmission spectra of an LPG pair under temperature variations; the spectrum was shifted with the same phase; (b) The amount of the spectrum shift with temperature; it was shifted toward longer wavelength with the sensitivity of ∼39 pm/°C; (c) The spectra under strain variations; only the phase was changed without affecting the envelop curve; (d) The amount of the phase shift measured with strain [48].

Mentions: Simultaneous measurements of several measurands are possible with the in-line MZI. By using the LPG pair made in double cladding fiber (DCF), we can simultaneously measure strain and temperature with minimizing the cross talk between them [48]. An LPG couples the core mode to several cladding modes of a fiber and this cladding modes are normally guided by the total internal reflection (TIR) at the cladding surface. In a conventional SMF, the fiber is jacketed with a resin material having a RI higher than the RI of the cladding material. Therefore, cladding modes are absorbed there, which prohibits the formation of an MZI with the coated jacket. However, for the DCF case, the cladding mode is guided by the inner cladding boundary, so that it can propagate regardless of the existence of any jacket material. Because of this property of the DCF, the grating-free region between two gratings of an LPG pair can be insensitive to physical contacts; moreover, it is possible to hold the grating-free region to isolate strain from thermal effect. Based on this, the simultaneous sensor could be made by applying strain only at the grating-free region of an LPG pair, while temperature was applied to the whole region of the LPG pair. With this configuration, the phase and the envelope of the MZI interference fringes were thermally shifted with the same rate, but the strain shifted only the phase as shown with Figure 8. Therefore, we were able to measure temperature and strain simultaneously.


Interferometric fiber optic sensors.

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

(a) Transmission spectra of an LPG pair under temperature variations; the spectrum was shifted with the same phase; (b) The amount of the spectrum shift with temperature; it was shifted toward longer wavelength with the sensitivity of ∼39 pm/°C; (c) The spectra under strain variations; only the phase was changed without affecting the envelop curve; (d) The amount of the phase shift measured with strain [48].
© Copyright Policy
Related In: Results  -  Collection

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

f8-sensors-12-02467: (a) Transmission spectra of an LPG pair under temperature variations; the spectrum was shifted with the same phase; (b) The amount of the spectrum shift with temperature; it was shifted toward longer wavelength with the sensitivity of ∼39 pm/°C; (c) The spectra under strain variations; only the phase was changed without affecting the envelop curve; (d) The amount of the phase shift measured with strain [48].
Mentions: Simultaneous measurements of several measurands are possible with the in-line MZI. By using the LPG pair made in double cladding fiber (DCF), we can simultaneously measure strain and temperature with minimizing the cross talk between them [48]. An LPG couples the core mode to several cladding modes of a fiber and this cladding modes are normally guided by the total internal reflection (TIR) at the cladding surface. In a conventional SMF, the fiber is jacketed with a resin material having a RI higher than the RI of the cladding material. Therefore, cladding modes are absorbed there, which prohibits the formation of an MZI with the coated jacket. However, for the DCF case, the cladding mode is guided by the inner cladding boundary, so that it can propagate regardless of the existence of any jacket material. Because of this property of the DCF, the grating-free region between two gratings of an LPG pair can be insensitive to physical contacts; moreover, it is possible to hold the grating-free region to isolate strain from thermal effect. Based on this, the simultaneous sensor could be made by applying strain only at the grating-free region of an LPG pair, while temperature was applied to the whole region of the LPG pair. With this configuration, the phase and the envelope of the MZI interference fringes were thermally shifted with the same rate, but the strain shifted only the phase as shown with Figure 8. Therefore, we were able to measure temperature and strain simultaneously.

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