Advantages of Draw Tower Fiber over Traditional Fiber

Table of Contents

Introduction
ORMOCER® Coatings
     Standard ORMOCER® for Strain Measurements
     ORMOCER®-T for Temperature Measurements
Conclusion

Introduction

FBGS is regularly asked, "What makes your draw tower fiber better than traditional fiber?"

The answer is not a simple one as there are numerous factors that contribute to this. However, one of the most important is the coating material that FBGS has selected to use, as ORMOCER® provides them with unparalleled performance.

ORMOCER® short for Organic Modified Ceramics describes a family of hybrid polymer materials which offer certain unique properties applicable to various applications. They are made up of inorganic oxidic structures that are substituted or cross-linked by organic groups. A complex synthesis process means that the properties of the ORMOCER® are changeable to suit the application required.

General scheme showing the structure of Ormocer® coatings

Figure 1. General scheme showing the structure of Ormocer® coatings.

ORMOCER® is typically UV cured and is well adjusted to the production process of an optical fiber. Some of the key advantages of FBGS draw tower grating fiber are achieved as a result of the ORMOCER® coating.

ORMOCER® Coatings

FBGS offers two types of ORMOCER® coatings:

Standard ORMOCER® for Strain Measurements

The regular ORMOCER® coating is primarily designed for strain measurement applications and has the following features:

  • High adhesion to the fiber glass allowing direct fixation of the DTG’s without having to remove the coating
  • High E-modules to create a good strain transfer between fiber and the glue
  • Easy fiber manipulation allowing to remove the ORMOCER® coating for splicing without the application of chemical acids
  • Temperature operating range outperforming standard optical fiber coatings to support applications between -180 and +200 °C

Keep in mind that the standard Ormocer® coating is less suited for temperature measurements using a strain-free optical fiber configuration (free-hanging optical fiber). FBGS suggests the use of Ormocer®-T coating in this case.

ORMOCER®-T for Temperature Measurements

ORMOCER®-T is primarily designed for temperature measurement applications where a strain-free DTG fiber is employed.

The hygroscopicity of optical fiber coatings usually restricts the accuracy of FBG-based temperature sensors as the coating can induce undesirable strain effects when absorbing humidity. To handle this challenge, it is recommended to use Ormocer®-T as DTG coating. By using this coating, undesirable strain effects linked with changes in the relative humidity are not conveyed to the optical fiber. Thus, the precision of the temperature measurements is considerably enhanced.

Like the Ormocer® coating, the Ormocer®-T coated fibers have an excellent mechanical strength, can be used within a wide temperature range (-180 °C to 200 °C) and are easy to handle. Furthermore, the ORMOCER®-T coating enables stable temperature measurements up to 200 °C and beyond based on the sensor configuration and highest temperature exposure duration.

Keep in mind that the Ormocer®-T coating is less suited for strain measurements at higher temperatures because of the lower elastic modulus. The coating becomes too soft to properly transfer strain to the optical fiber. Standard Ormocer® coating is the ideal option in this case.

Conclusion

To conclude, the standard Ormocer® coating is most suited for strain measurements (using bonded fibers), while the Ormocer®-T coating is the chosen coating for temperature measurements (unbonded free fibers).

Note: ORMOCER® is a Trademark of Fraunhofer-Gesellschaft zur Forderung 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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