Limits...
Fiber-Optic Sensors for Measurements of Torsion, Twist and Rotation: A Review †

View Article: PubMed Central - PubMed

ABSTRACT

Optical measurement of mechanical parameters is gaining significant commercial interest in different industry sectors. Torsion, twist and rotation are among the very frequently measured mechanical parameters. Recently, twist/torsion/rotation sensors have become a topic of intense fiber-optic sensor research. Various sensing concepts have been reported. Many of those have different properties and performances, and many of them still need to be proven in out-of-the laboratory use. This paper provides an overview of basic approaches and a review of current state-of-the-art in fiber optic sensors for measurements of torsion, twist and/or rotation.

No MeSH data available.


Feasible arrangements for forward and backward coupling of cladding modes in TFBGs. (a) Back cladding modes coupling; (b) Forward cladding modes coupling; (c) Radiation modes coupling.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC5375729&req=5

sensors-17-00443-f020: Feasible arrangements for forward and backward coupling of cladding modes in TFBGs. (a) Back cladding modes coupling; (b) Forward cladding modes coupling; (c) Radiation modes coupling.

Mentions: In general, this type of grating can couple light from the fundamental core mode to the cladding modes of the fiber effectively. A detailed theatrical background on the coupling process and conditions in TFBGs is, for example, presented in [92]. This coupling occurs in a resonant way, i.e., when phase matching conditions between the guided core and the cladding modes are met [93,94]:(4)λFM−CLM=Λcosθ(neff_FM±neff_CLM)where neff_FM is the effective index of the fundamental core mode, neff_CLM the effective index of the m-th cladding mode, θ is the grating tilt (measured as the angle between the grating tilt plane and plane normal to the fiber axis), and λFM-CLM represents the resonance wavelength at which mode coupling occurs. Depending on the grating tilt θ, the mode coupling may be divided into three regimes [92] as shown in Figure 20: if the grating tilt is less than 45°, the forward propagating mode will be coupled to the backward propagating cladding (or radiation) modes (Figure 20a). If the grating tilt is more than 45°, the forward propagating mode will be coupled to the forward propagating cladding (or radiation) modes (Figure 20b). If the tilt corresponds θ = 45°, then the light can be coupled out of the fiber and this condition can be used to build fiber polarizers (Figure 20c) [95]. Forward-propagating configurations (grating tilt is more than 45°) are, perhaps, used most frequently in twist/rotation sensing, as shown further below, due to the very distinctive polarization response.


Fiber-Optic Sensors for Measurements of Torsion, Twist and Rotation: A Review †
Feasible arrangements for forward and backward coupling of cladding modes in TFBGs. (a) Back cladding modes coupling; (b) Forward cladding modes coupling; (c) Radiation modes coupling.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5375729&req=5

sensors-17-00443-f020: Feasible arrangements for forward and backward coupling of cladding modes in TFBGs. (a) Back cladding modes coupling; (b) Forward cladding modes coupling; (c) Radiation modes coupling.
Mentions: In general, this type of grating can couple light from the fundamental core mode to the cladding modes of the fiber effectively. A detailed theatrical background on the coupling process and conditions in TFBGs is, for example, presented in [92]. This coupling occurs in a resonant way, i.e., when phase matching conditions between the guided core and the cladding modes are met [93,94]:(4)λFM−CLM=Λcosθ(neff_FM±neff_CLM)where neff_FM is the effective index of the fundamental core mode, neff_CLM the effective index of the m-th cladding mode, θ is the grating tilt (measured as the angle between the grating tilt plane and plane normal to the fiber axis), and λFM-CLM represents the resonance wavelength at which mode coupling occurs. Depending on the grating tilt θ, the mode coupling may be divided into three regimes [92] as shown in Figure 20: if the grating tilt is less than 45°, the forward propagating mode will be coupled to the backward propagating cladding (or radiation) modes (Figure 20a). If the grating tilt is more than 45°, the forward propagating mode will be coupled to the forward propagating cladding (or radiation) modes (Figure 20b). If the tilt corresponds θ = 45°, then the light can be coupled out of the fiber and this condition can be used to build fiber polarizers (Figure 20c) [95]. Forward-propagating configurations (grating tilt is more than 45°) are, perhaps, used most frequently in twist/rotation sensing, as shown further below, due to the very distinctive polarization response.

View Article: PubMed Central - PubMed

ABSTRACT

Optical measurement of mechanical parameters is gaining significant commercial interest in different industry sectors. Torsion, twist and rotation are among the very frequently measured mechanical parameters. Recently, twist/torsion/rotation sensors have become a topic of intense fiber-optic sensor research. Various sensing concepts have been reported. Many of those have different properties and performances, and many of them still need to be proven in out-of-the laboratory use. This paper provides an overview of basic approaches and a review of current state-of-the-art in fiber optic sensors for measurements of torsion, twist and/or rotation.

No MeSH data available.