We are regularly asked, "What makes your draw tower fiber better than traditional fiber?"
The answer is not a simple one as there are many factors that contribute to this. However one of the most significant is the coating material that we have chosen to use, as ORMOCER® provides us with unparalleled performance.
ORMOCER® short for Organic Modified Ceramics describes a group of hybrid polymer materials which offer some unique properties applicable to different applications. They are composed of inorganic oxidic structures, that are cross-linked or substituted by organic groups. A complex synthesis process means that the properties of the ORMOCER® are adjustable to suit the application required.
Fig. 1: General scheme showing the structure of Ormocer® coatings
ORMOCER® is mostly UV cured and is well adapted to the production process of an optical fiber. Some of the main advantages of FBGS draw tower grating fiber are achieved as a result of the ORMOCER® coating.
FBGS offers two types of ORMOCER© coatings:
1) Standard ORMOCER® for strain measurements
The standard ORMOCER® coating is mainly designed for strain measurement applications and has the following features:
Please note the standard Ormocer® coating is less suited for temperature measurements using a strain-free optical fiber configuration (free-hanging optical fiber). We recommend to use Ormocer®-T coating in this case.
2) ORMOCER®-T for temperature measurements
ORMOCER®-T is mainly designed for temperature measurement applications where a strain-free DTG fiber is used.
The hygroscopicity of optical fiber coatings typically limits the accuracy of FBG-based temperature sensors as the coating can induce unwanted strain effects when absorbing humidity. To overcome this challenge, it is recommended to use Ormocer®-T as DTG coating. By using this coating, unwanted strain effects associated with changes in the relative humidity are not transferred to the optical fiber. Therefore, the precision of the temperature measurements is significantly enhanced.
Similar to the Ormocer® coating, the Ormocer®-T coated fibers have a superior mechanical strength, are easy to handle and can be used within a wide temperature range (-180°C to 200°C). Moreover, the ORMOCER®-T coating enables stable temperature measurements up to 200°C and beyond depending on the sensor configuration and maximum temperature exposure duration.
Please note however the Ormocer®-T coating is less suited for strain measurements at elevated temperatures due to the lower elastic modulus. The coating is getting too soft to properly transfer strain to the optical fiber. Standard Ormocer® coating is the preferred option in this case.
As conclusion, the standard Ormocer® coating is best suited for strain measurements (using bonded fibers), whereas the Ormocer®-T coating is the preferred coating for temperature measurements (unbonded free fibers).
ORMOCER® is a Trademark of Fraunhofer-Gesellschaft zur Forderung der angewandten Forschung e.V.