Draw Tower Gratings – The Advantages

In the field of Fiber Bragg Grating sensing, Draw Tower Gratings have certain unique properties that makes them the chosen product for a number of FBG applications.

A demonstration of these advantages can be found in the following video.


Extremely High Mechanical Strength

Draw Tower Gratings display very high mechanical strength compared to conventional produced gratings as illustrated in Figure 1. The mechanical strength of DTG®s and regular recoated FBGs is analyzed by applying increasing tensile stress to the samples until the fiber breaks. The test has been done using a commercial material testing machine in compliance with IEC 793-1 and consists of a fatigue test with three different elongation speeds of 3, 30, 300 mm/minute. 15 samples per speed were analyzed. The breaking force is captured and plotted in a diagram of relative breaking probability (Weibull plots).

As can be seen in Figure 1, the mechanical strength of the DTG®s is approximately five times higher compared to classical recoated FBGs.

Relative breaking probability of Draw Tower Gratings and standard telecom fiber

Figure 1. Relative breaking probability of Draw Tower Gratings and standard telecom fiber.

Spliceless Arrays

The Draw Tower Grating technology allows for the production of spliceless grating chains with a great number of sensor elements. Figure 2 illustrates the spectrum of an array of 80 DTGs on a single fiber, all with a different wavelength.

Spectrum of a DTG array containing 80 different wavelengths

Figure 2. Spectrum of a DTG array containing 80 different wavelengths.

Direct Fixation

The coating that is applied on the DTGs is an Organic Modified Ceramic (ORMOCER®1). This coating exhibits superior adhesion properties to the fiber glass, which makes DTG®s directly applicable for fixation on structures without coating removal. This not only facilitates the installation process, but also boosts the reliability.

Uniform Coating Coverage

The coating is applied after the writing of the DTG. Therefore, no stripping and recoating process is necessary anymore. DTGs have thus the unique property that the coating is uniform over the total length of the fiber, even on the position of the DTGs itself.

High Operating Temperature Range

The coating of the DTG®s is the factor that restricts the temperature operating range. DTG®s are coated with ORMOCER®1 material and thus temperatures between -180 and +200 °C can be applied.

Low Bending Loss

Because of the used glass composition, the standard DTG® fiber has very low bending losses which allow the operation of the fibers in configurations with low bending radii without having major attenuation effects.

High Repeatability

DTG®s are made using an automated production procedure. This procedure controls the production parameters very accurately and assures high quality and repeatability.

Relatively Low Cost

Due to the fact that the DTG®s are produced using a complete automatic production process, they can be created at a slightly low cost, particularly for high and medium volume orders.


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

This information has been sourced, reviewed and adapted from materials provided by FBGS Technologies GmbH.

For more information on this source, please visit FBGS Technologies GmbH.


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