Limits...
Compact Optical Fiber 3D Shape Sensor Based on a Pair of Orthogonal Tilted Fiber Bragg Gratings.

Feng D, Zhou W, Qiao X, Albert J - Sci Rep (2015)

Bottom Line: In this work, a compact fiber-optic 3D shape sensor consisting of two serially connected 2° tilted fiber Bragg gratings (TFBGs) is proposed, where the orientations of the grating planes of the two TFBGs are orthogonal.The measurement of the reflective transmission spectrum from the pair of TFBGs was implemented by Fresnel reflection of the cleaved fiber end.In the third (axial) direction, the strain is obtained directly by the shift of the TFBG Bragg wavelengths with a sensitivity of 1.06 pm/με.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, Northwest University, Xi'an, 710069, China.

ABSTRACT
In this work, a compact fiber-optic 3D shape sensor consisting of two serially connected 2° tilted fiber Bragg gratings (TFBGs) is proposed, where the orientations of the grating planes of the two TFBGs are orthogonal. The measurement of the reflective transmission spectrum from the pair of TFBGs was implemented by Fresnel reflection of the cleaved fiber end. The two groups of cladding mode resonances in the reflection spectrum respond differentially to bending, which allows for the unique determination of the magnitude and orientation of the bend plane (i.e. with a ± 180 degree uncertainty). Bending responses ranging from -0.33 to + 0.21 dB/m(-1) (depending on orientation) are experimentally demonstrated with bending from 0 to 3.03 m(-1). In the third (axial) direction, the strain is obtained directly by the shift of the TFBG Bragg wavelengths with a sensitivity of 1.06 pm/με.

No MeSH data available.


Related in: MedlinePlus

Transmission spectra of the dual orthogonal TFBGs for various curvatures.Insets show the bending-induced spectral responses of the cladding mode resonances around 1565.8 nm (TFBG1) and 1585.2 nm (TFBG2), respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4663507&req=5

f2: Transmission spectra of the dual orthogonal TFBGs for various curvatures.Insets show the bending-induced spectral responses of the cladding mode resonances around 1565.8 nm (TFBG1) and 1585.2 nm (TFBG2), respectively.

Mentions: The proposed sensing system is shown in Fig. 1. Here we used two TFBGs with a tilt angle φ of 2 degree connected in series with their tilt orientation at ~90 degrees from each other, a followed by a cleaved end face acting as a mirror. The 2D bending in the plane perpendicular to the fiber axis is first described. A tilt direction ξ relative to the horizontal axis of the transverse coordinate system and a spatial bending direction δ are defined respectively for orienting the device in three dimensional space, as shown in Fig. 1(b). Each grating has a length of 10 mm. The distance between TFBG1and TFBG2 is 3 mm. The reflected spectrum of the fabricated sensing structure is shown in Fig. 2 for several curvature values from 0 to 3.03 m−1. The large positive peaks correspond to the core mode coupling (Bragg peak) from the two wavelength-offset gratings and they remain unaffected by bending, as expected. Narrowband dips in the spectrum correspond to light extracted from the core and coupled to individual cladding modes. For each of the gratings a zoomed inset shows a spectral region located approximately 3 nm away from the Bragg peak where clear measurable changes can be observed upon bending. For each of the gratings a zoomed inset shows a spectral region located approximately 3 nm away from the Bragg peak where clear measurable changes can be observed upon bending. In particular, there is a resonance located exactly 3.2 nm away from each Bragg peak that is seen to increase in amplitude (near 1565.8 nm) for one grating TFBG1 and to decrease (near 1585.2 nm) for the other grating TFBG2. The difference is due to the angle between the direction of bending and the tilt plane of the gratings. It is important to point out that the most directionally sensitive resonance in each spectrum (i.e. in each TFBG) is unambiguously identifiable by its wavelength relative to the Bragg peak wavelength. The phase matching condition between the core mode and each cladding mode imposes a one to one relationship between the resonance position and the cladding mode to which the grating couples the incident core mode guided light. For a TFBG with a tilt angle φ, the standard phase matching condition can be expressed by the wavelength (λi) where the resonance is observed as follows18:


Compact Optical Fiber 3D Shape Sensor Based on a Pair of Orthogonal Tilted Fiber Bragg Gratings.

Feng D, Zhou W, Qiao X, Albert J - Sci Rep (2015)

Transmission spectra of the dual orthogonal TFBGs for various curvatures.Insets show the bending-induced spectral responses of the cladding mode resonances around 1565.8 nm (TFBG1) and 1585.2 nm (TFBG2), respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4663507&req=5

f2: Transmission spectra of the dual orthogonal TFBGs for various curvatures.Insets show the bending-induced spectral responses of the cladding mode resonances around 1565.8 nm (TFBG1) and 1585.2 nm (TFBG2), respectively.
Mentions: The proposed sensing system is shown in Fig. 1. Here we used two TFBGs with a tilt angle φ of 2 degree connected in series with their tilt orientation at ~90 degrees from each other, a followed by a cleaved end face acting as a mirror. The 2D bending in the plane perpendicular to the fiber axis is first described. A tilt direction ξ relative to the horizontal axis of the transverse coordinate system and a spatial bending direction δ are defined respectively for orienting the device in three dimensional space, as shown in Fig. 1(b). Each grating has a length of 10 mm. The distance between TFBG1and TFBG2 is 3 mm. The reflected spectrum of the fabricated sensing structure is shown in Fig. 2 for several curvature values from 0 to 3.03 m−1. The large positive peaks correspond to the core mode coupling (Bragg peak) from the two wavelength-offset gratings and they remain unaffected by bending, as expected. Narrowband dips in the spectrum correspond to light extracted from the core and coupled to individual cladding modes. For each of the gratings a zoomed inset shows a spectral region located approximately 3 nm away from the Bragg peak where clear measurable changes can be observed upon bending. For each of the gratings a zoomed inset shows a spectral region located approximately 3 nm away from the Bragg peak where clear measurable changes can be observed upon bending. In particular, there is a resonance located exactly 3.2 nm away from each Bragg peak that is seen to increase in amplitude (near 1565.8 nm) for one grating TFBG1 and to decrease (near 1585.2 nm) for the other grating TFBG2. The difference is due to the angle between the direction of bending and the tilt plane of the gratings. It is important to point out that the most directionally sensitive resonance in each spectrum (i.e. in each TFBG) is unambiguously identifiable by its wavelength relative to the Bragg peak wavelength. The phase matching condition between the core mode and each cladding mode imposes a one to one relationship between the resonance position and the cladding mode to which the grating couples the incident core mode guided light. For a TFBG with a tilt angle φ, the standard phase matching condition can be expressed by the wavelength (λi) where the resonance is observed as follows18:

Bottom Line: In this work, a compact fiber-optic 3D shape sensor consisting of two serially connected 2° tilted fiber Bragg gratings (TFBGs) is proposed, where the orientations of the grating planes of the two TFBGs are orthogonal.The measurement of the reflective transmission spectrum from the pair of TFBGs was implemented by Fresnel reflection of the cleaved fiber end.In the third (axial) direction, the strain is obtained directly by the shift of the TFBG Bragg wavelengths with a sensitivity of 1.06 pm/με.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, Northwest University, Xi'an, 710069, China.

ABSTRACT
In this work, a compact fiber-optic 3D shape sensor consisting of two serially connected 2° tilted fiber Bragg gratings (TFBGs) is proposed, where the orientations of the grating planes of the two TFBGs are orthogonal. The measurement of the reflective transmission spectrum from the pair of TFBGs was implemented by Fresnel reflection of the cleaved fiber end. The two groups of cladding mode resonances in the reflection spectrum respond differentially to bending, which allows for the unique determination of the magnitude and orientation of the bend plane (i.e. with a ± 180 degree uncertainty). Bending responses ranging from -0.33 to + 0.21 dB/m(-1) (depending on orientation) are experimentally demonstrated with bending from 0 to 3.03 m(-1). In the third (axial) direction, the strain is obtained directly by the shift of the TFBG Bragg wavelengths with a sensitivity of 1.06 pm/με.

No MeSH data available.


Related in: MedlinePlus