Adhesive-Free Capillary Splicing for Fiber Bragg Grating Sensors
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Solution Overview
Problem
Existing methods for attaching a capillary to an optical fiber for temperature sensing using fiber Bragg gratings suffer from signal attenuation and potential functional failure due to adhesive use and mechanical sensitivity to external disturbances.
Innovation Solution
A fastening method involving a capillary with a lower melting temperature than the optical fiber, where the capillary is heated and spliced to the fiber without adhesives, ensuring a secure, non-invasive connection that maintains the optical path integrity and decouples the sensor area from mechanical influences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If adhesive is used to attach the capillary to the optical fiber, then the mechanical connection is achieved, but the temperature sensitivity is degraded and the adhesive may creep and clog the fiber Bragg grating
Solution Approach 1:
The adhesive is completely removed from the system. Instead of using adhesive to attach the capillary to the optical fiber, the patent employs a mechanical attachment method where the capillary is directly secured to the fiber using a clamp or holder structure, eliminating the harmful adhesive substance that causes creep and clogging while maintaining reliable mechanical connection.
Solution Approach 2:
A mechanical clamp or holder structure serves as an intermediary component between the capillary and the optical fiber. This intermediary provides a secure mechanical attachment without requiring adhesive, allowing the capillary to be firmly connected to the fiber while preventing any material from creeping into the fiber Bragg grating region.
2Reliability
If the optical path is spliced directly to a fused silica capillary, then the mechanical attachment is achieved, but significant signal attenuation occurs
Solution Approach 1:
The attachment structure is segmented into distinct functional zones: a mechanical clamping region for secure attachment, a transition region for gradual impedance matching, and an optical transmission region with minimal interference. This segmentation allows the mechanical attachment to be achieved without creating significant optical impedance mismatches that cause signal attenuation.
Solution Approach 2:
The capillary and attachment structure are designed with locally optimized properties: the attachment portion has mechanical strength for reliable connection, while the optical path portion has optimized optical properties (refractive index, diameter) to minimize signal attenuation. The transition between these zones is gradual to avoid abrupt impedance changes.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method provides a reliable, adhesive-free connection that minimizes signal attenuation and maintains the temperature sensitivity of the fiber Bragg grating sensor, preventing adhesive creep and ensuring the optical path remains unaffected.
Implementation Method 1
heating the fastening region of the capillary to a heating temperature equal to or greater than the second melting temperature
Implementation Method 2
a detector which is configured to detect a marking on the capillary
Data Source
Figure 1~2
Figure 3
AI summary
A fastening device is described, comprising: an insertion area (51) for a capillary (20) that at least partially surrounds a sensor area (11) of an optical fiber (10), the capillary (20) comprising a fastening area (21) that can be arranged spaced apart from the sensor area (11) of the optical fiber (10); a detector (52) configured to detect a mark (22) on the capillary (20) provided on the capillary (20) to indicate the fastening area (21) of the capillary (20); and a heating area (53) configured to heat the fastening area (21) of the capillary (20), preferably automatically, for a predetermined duration when the detector (52) detects the mark (22). The fastening device is usable for performing a fastening process.