Distributed Temperature Measurement Optical Cable Splicing

Optical fiber splicing in DTS systems is typically performed using fusion splicing to ensure minimal signal loss and high measurement accuracy along the fiber.

Overview of DTS Optical Fiber Splicing

In Distributed Temperature Sensing (DTS) systems, the optical fiber acts as a continuous sensor along its entire length, detecting temperature changes via Raman or Brillouin scattering . Any discontinuity or high-loss connection can degrade the backscattered signal, reducing spatial resolution and accuracy. Therefore, proper splicing is critical for maintaining system performance.

Splicing Methods

1. Fusion Splicing
   • Process: Fusion splicing involves aligning the fiber cores precisely and using an electric arc to melt and fuse the fibers together.
   • Advantages: Provides the lowest insertion loss (typically 0.02–0.05 dB per splice) and minimal back reflection, which is essential for long-distance DTS measurements .
   • Applications: Preferred for permanent installations in power cables, pipelines, or tunnels where the fiber may span tens of kilometers .
   • Considerations: Requires a fusion splicer, careful fiber preparation (stripping, cleaning, cleaving), and protective sleeves to prevent mechanical damage.
2. Mechanical Splicing
   • Process: Fibers are aligned within a precision mechanical fixture and held together with index-matching gel or adhesive.
   • Advantages: Quick and does not require expensive fusion equipment.
   • Disadvantages: Higher insertion loss (0.1–0.3 dB per splice) and potential for signal degradation over time, making it less suitable for high-accuracy DTS applications .
   • Applications: Temporary connections or field repairs where fusion splicing is not feasible.

Protective Measures

• Splice Protection Sleeves: After splicing, fibers are enclosed in heat-shrink or mechanical sleeves to protect against environmental stress, vibration, and temperature extremes .
• Cable Routing: Splices should be located in accessible, low-stress areas, avoiding sharp bends or mechanical strain that could affect the DTS signal.
• Testing: Each splice should be tested using an Optical Time Domain Reflectometer (OTDR) to verify low loss and proper alignment before final installation .

Best Practices

• Minimize the number of splices along the fiber to reduce cumulative loss.
• Use high-quality cleaving tools to ensure smooth fiber ends.
• Maintain a clean environment during splicing to prevent contamination.
• Document splice locations and loss values for future maintenance and troubleshooting.

Summary

For DTS systems, fusion splicing is the recommended method due to its low loss, high reliability, and minimal impact on temperature measurement accuracy. Mechanical splicing can be used for temporary or emergency repairs but is generally avoided in permanent installations. Proper protection, testing, and careful handling of splices are essential to ensure the long-term performance of distributed temperature measurement systems .