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Draw Tower Gratings (DTG®)

We offer three types of DTG® with unique characteristics compared to classically produced FBGs, such as extremely high breaking-strength, spliceless array configuration and uniform coating coverage. FBG parameters and coating material can be selected based on customer needs.

DTG®s in low bend loss fiber

1550-125

Draw Tower Gratings (DTG®s) written in Low Bend Loss fiber LBL-1550-125 which has a cladding diameter of 125µm and is optimized for operation in the 1550nm wavelength window. The glass composition has been tuned such that the fiber maintains a good signal transmission under small bending diameters.

830-125

Draw Tower Gratings (DTG®s) written in Low Bend Loss fiber LBL-830-125 which has a cladding diameter of 125µm and is optimized for operation in the 830nm wavelength window. The glass composition has been tuned such that the fiber maintains a good signal transmission under small bending diameters.

 

DTG®s in reduced cladding fibers

Draw Tower Gratings (DTG®s) written into Low Bend Loss fiber LBL-1550-80 which has a cladding diameter of 80μm and is optimized for operation in the 1550nm wavelength window. The reduced cladding diameter offers several major advantages compared to standard 125µm fibers:

  1. Unobtrusiveness – particularly interesting for embedding applications including carbon composite structures and medical catheters.
  2. Increased sensitivity – less force is required to strain the fiber enhancing the performance of sensors based on force or acoustic sensing.
  3. Reduced bending radii – lower surface strain levels enabling more compact sensor designs.

Overview

Parameter Low Bend Loss Fiber 1550-125 Low bend loss fiber 830-125 Reduced cladding fibers
Reflectivity (for grating length of 8mm) > 15%
FWHM (for grating length of 8mm) 100 pm 30 pm 100 pm
Centre wavelength (extended range upon request) 1510–159 0 nm 1460–1620 nm 810–860 nm 1510–159 0 nm 1460–1620 nm
Absolute wavelength accuracy¹ ≤ 0.5 nm ≤ 0.8 nm ≤ 0.5 nm ≤ 0.5 nm ≤ 0.8 nm
Relative wavelength accuracy ≤ 0.3 nm ≤ 0.5 nm ≤ 0.3 nm ≤ 0.3 nm ≤ 0.5 nm
Side Lobe Suppression (SLS) ≥ 10 dB (typical)
DTG® length 1–10 mm / 8 mm (typical)
Attenuation < 8.6 dB/km < 18.4 dB / km < 8.6 dB/km
Mode Field Diameter (MFD) @ 1550 nm 6 μm (typical) 5 μm (typical) 6 μm (typical)
Numerical Aperture (NA) 0.26 (typical)
Cladding diameter 125 μm ± 1 μm 80 μm ± 1 μm
Coating type² ORMOCER®/ORMOCER®-T / One layer Acrylate
Coated fiber diameter 195 μm (typical) 120 μm (typical)
Tensile load at break³ > 50 N (corresponds to >5% strain) > 20 N (corresponds to >5% strain)
Temperature sensitivity⁴ (formula: Δλ/(λ ⋅ ΔT) ) 6.5 K-1 ⋅ 10-6 (typical)
Strain sensitivity¹ (formula: Δλ/(λ ⋅ Δε) ) 7.8 με-1 ⋅ 10-7 (typical)
Operational temperature range -200–200°C for ORMOCER®
-20–200°C for ORMOCER®-T
-20–90°C for One layer Acrylate

1 measured at room temperature
2 ORMOCER® is mainly applied for strain measurements while ORMOCER®-T is recommended for temperature measurements.
3 according to IEC-60793-1-31 using a constant displacement of 30 mm/minute
4 measured between 0°C and 70°C
5 Temperature range is dependent on exposure time.

ORMOCER®: trademark of Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V.

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Draw Tower Gratings (DTGs) are produced using a process that combines the drawing of the optical fiber with the writing of the grating. The input of the process is a glass preform. After heating the preform, the pulling and formation of the fibre will be initiated. Further in the production process, the fiber crosses the optical axis of a laser and the interferometer that create a periodical UV-light interference pattern in order to write the grating.  Using a pulse selector and taking into account the draw speed, FBGs can be accurately positioned in the fiber. When the grating has been written the fiber is coated by entering a coating reservoir, followed by a curing step of the coating. Finally the location of the DTG is marked automatically and the fiber is reeled onto a drum. This process of simultaneously drawing the fiber, writing the grating and coating the fiber directly after the grating inscription, results in high strength grating chains. As such the commonly used stripping and recoating process of standard FBGs is not necessary and the pristine fiber strength is maintained during the DTG manufacturing process.

Cases for Draw Tower Gratings (DTG®)

Spatial Strain Sensing Using Embedded Fiber Optics

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We are committed to respecting your privacy and protecting your personal information and will always treat it with the upmost care. You can find out how we handle your data and all the ways we use it to provide you with a better service in our Privacy Statement.

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Germany

FBGS Technologies GmbH
Winzerlaer Straße 2
D-07745 Jena

Belgium

FBGS International NV
Bell Telephonelaan 2H

B-2440 Geel

China

X2 Suzhou Electronic Technology
Room 103, No. 388
Xinping Str. SIP, Suzhou