Long-range Raman distributed temperature sensor with high spatial and temperature resolution using graded-index...

Area of Science:

• Optical Fiber Technology
• Sensing and Measurement

Background:

• Raman distributed temperature sensing (RDTS) systems require advanced optical fibers for high-resolution, long-distance measurements.
• Standard single-mode fibers (SMF) and multi-mode fibers (MMF) have limitations in achieving both high spatial and temperature resolution simultaneously over extended ranges.

Purpose of the Study:

• To design and fabricate a graded-index few-mode fiber (GI-FMF) optimized for RDTS.
• To evaluate the performance of the GI-FMF in terms of spatial and temperature resolution for long-distance sensing applications.

Main Methods:

• Fabrication of a GI-FMF with a large effective mode area and low intermodal dispersion.
• Experimental measurement of spatial and temperature resolution using a commercial RDTS system with GI-FMF, standard MMF, and standard SMF.
• Testing under different launch conditions, including overfilled launch and quasi-single mode operation.

Main Results:

• GI-FMF under overfilled launch achieved 1°C temperature resolution and 1.13m spatial resolution at 25 km.
• Standard MMF showed degraded spatial resolution (2.58m) with slightly higher temperature resolution.
• GI-FMF under quasi-single mode operation offered a 4.7°C temperature resolution with no spatial resolution degradation compared to SMF.

Conclusions:

• The developed GI-FMF significantly improves RDTS performance, offering superior temperature and spatial resolution over long distances.
• GI-FMF in few-mode operation provides comparable temperature resolution to MMF with minimal impact on spatial resolution.
• GI-FMF in quasi-single mode operation enhances temperature resolution compared to SMF without compromising spatial resolution.