How to check the incoming and outgoing temperatures during optical fiber splicing

Incoming and outgoing temperatures during optical fiber splicing can be monitored using fusion splicer control systems, Raman-based fiber optic temperature sensing, or Brillouin OTDR distributed sensing.

Fusion Splicer Temperature Control

During fusion splicing, the fiber ends are heated by an electric arc to fuse them together. Modern fusion splicers can measure and control the temperature of the splice region by observing the behavior of the fiber ends under heat. Specifically, the surface tension effect causes the fiber ends to gradually align as they soften. By measuring the offset of the fiber ends over time, the splicer can calculate the temperature of the heated fiber portions and compare it to a predetermined set value to ensure proper fusion without overheating or underheating (incoming temperature control) and to maintain consistent splice quality (outgoing temperature control) during the process .

Distributed Temperature Sensing Along the Fiber

For monitoring temperature along the fiber after splicing, Raman-based fiber optic temperature measurement can be used. A short laser pulse is sent through the fiber, and the backscattered light is analyzed. The ratio of Stokes to anti-Stokes intensities provides the temperature at specific points along the fiber. This method allows for high spatial resolution (≈0.7 m) and accuracy better than 0.1°C over distances up to 10 km, enabling technicians to detect temperature variations that could affect splice performance or fiber integrity .

Brillouin OTDR for Strain and Temperature

Another approach is using Brillouin Optical Time Domain Reflectometry (B-OTDR), which allows the fiber itself to act as a distributed sensor. By measuring the Brillouin frequency shift along the fiber, technicians can detect temperature changes and strain at splice points or along the cable route. This method is particularly useful for identifying hot spots, abnormal splice events, or areas at risk of thermal damage, providing both incoming and outgoing temperature information indirectly through the fiber's response .

Practical Considerations

• Ensure the fusion splicer is calibrated and the electrodes are in good condition.
• Maintain balanced tension on the fibers to avoid microbends that can affect temperature readings and splice quality .
• For long-term monitoring, integrate distributed temperature sensing to detect environmental or operational temperature changes that could impact the splice.
• Use dual-wavelength OTDR measurements to cross-check for bends or anomalies that may influence local heating or cooling along the fiber . By combining real-time splicer temperature control with distributed sensing techniques, technicians can effectively monitor both the incoming heat applied during splicing and the outgoing temperature along the fiber, ensuring high-quality, low-loss splices and long-term fiber reliability.