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DTG & FSG Technology

DTG® & FSG Technology is one of Europe‘s largest energy research organizations, focussed on sustainable energy generation to develop safe, efficient, reliable and environmentally friendly energy systems. It has a strong international position in the fields of biomass, solar energy, wind energy, energy efficiency and policy studies

Draw Tower Gratings (DTG®)

Draw Tower Gratings (DTG®s) are produced using a process that combines the drawing of the optical fiber with the writing of the grating.

The figure below shows the set-up of this production process. The input of the process is a glass pre-form. After heating the pre-form, the pulling and formation of the fiber will be initiated.

WHY USING DTG® OR FSG®?

DTG®s and FSG®s offer 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.

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 FBG 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.

Finally the location of the FBG 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.

BU/Link_ Fiber Optic load monitoring of wind turbine blades

 

FemtoSecond Gratings (FSG®)

FBGS’s FemtoSecond Grating (FSG®) technology complements the existing DTG® technology by adding new manufacturing capabilities due to special demands for Fiber Bragg Gratings (FBGs).

The fabrication processes of both techniques maintain the pristine high mechanical- strength of the optical fiber. In addition, FSG®s can provide sensor configurations and features needed for special applications.

FSG® exploits the through-coating FBG inscription process, which utilizes ultrafast laser pulses launched via special optics to the fiber core without damaging the fiber coating. See below the schematic for FSG® inscription.

BU/Link_ Fiber Optic load monitoring of
wind turbine blades

The focused high-power laser pulses change the index of refraction of the glass material in the core of the optical fiber due to nonlinear absorption processes. These effects are nearly independent of the doping level of the optical fiber or the type of glass, which uniquely sets this process to offer an advantage in its ability to modify any type of optical fiber.
The laser pulses are guided via special optics to form a unique interference pattern, which is geometrically co-aligned with the longitudinal axis of a stationary standard optical fiber. The impinging pattern creates the desired modulated index of refraction onto a selected local length along the core of the optical fiber.

This inscription defines the required reflected Bragg wavelength. In addition, an array of desired FBGs can be inscribed by translating the optical fiber along its longitudinal axis.

Advantages of FSG®

  • Temperature measurements using FBGs is an absolute measurement. There is always a unique relationship between wavelength and temperature.
  • FBGs have due to their small size and volume a fast temperature response time which is needed for the measurement of fast temperature changes.
  • FBG based temperature sensors can become read out over large distances, without the need of amplification means under way (>20km).
  • Due to the nature of the glass, FBG based temperature sensors show a good corrosion resistance.

 

Advantages of DTG® & FSG®

1 Extremely high medical strength

The focused high-power laser pulses change the index of refraction of the glass material in the core of the optical fiber due to nonlinear absorption processes. These effects are nearly independent of the doping level of the optical fiber or the type of glass, which uniquely sets this process to offer an advantage in its ability to modify any type of optical fiber.
The laser pulses are guided via special optics to form a unique interference pattern, which is geometrically co-aligned with the longitudinal axis of a stationary standard optical fiber. The impinging pattern creates the desired modulated index of refraction onto a selected local length along the core of the optical fiber.

This inscription defines the required reflected Bragg wavelength. In addition, an array of desired FBGs can be inscribed by translating the optical fiber along its longitudinal axis. This inscription defines the required reflected Bragg wavelength.

2 XXXX

The focused high-power laser pulses change the index of refraction of the glass material in the core of the optical fiber due to nonlinear absorption processes. These effects are nearly independent of the doping level of the optical fiber or the type of glass, which uniquely sets this process to offer an advantage in its ability to modify any type of optical fiber.
The laser pulses are guided via special optics to form a unique interference pattern, which is geometrically co-aligned with the longitudinal axis of a stationary standard optical fiber. The impinging pattern creates the desired modulated index of refraction onto a selected local length along the core of the optical fiber.

This inscription defines the required reflected Bragg wavelength. In addition, an array of desired FBGs can be inscribed by translating the optical fiber along its longitudinal axis. This inscription defines the required reflected Bragg wavelength.

3 Abc

This inscription defines the required reflected Bragg wavelength. In addition, an array of desired FBGs can be inscribed by translating the optical fiber along its longitudinal axis. This inscription defines the required reflected Bragg wavelength.

Comparison of DTG® & FSG® Technology

Customized FSG® FSG®-A01 DTG®-AXXX
High strength yes yes yes
Uniform coating coverage yes yes yes
Ge doping level any (incl. pure silica) low high
Fiber diameter 80 μm
125 μm
125 μm 80 μm
125 μm
Number of gratings in an array high medium unlimited
Coating type any (transparent) polyimide Ormocer®
Ormocer®-T
acrylate
Standard wavelength range any (on request) 1510 – 1590 nm 1460 – 1620 nm
Reflectivity any (on request) medium to high low to medium
Bend insensitivity any (on request) medium high
Fiber attenuation any (on request) low medium
Temperature stability high high medium
Most cost effective for low density grating low density grating high density grating

 

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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