OFDR-based shape sensor using a plane-by-plane-inscribed weak FBG array in multicore fiber

Area of Science:

• Fiber optic sensing
• Optical instrumentation
• Materials science

Background:

• Fiber Bragg gratings (FBGs) are widely used for sensing applications.
• Multicore fiber (MCF) offers increased sensing capacity and multiplexing capabilities.
• Existing FBG inscription techniques can be complex and time-consuming.

Purpose of the Study:

• To demonstrate an Optical Frequency Domain Reflectometry (OFDR)-based shape sensor.
• To develop a novel method for inscribing weak fiber Bragg gratings (WFBGs) in MCF.
• To achieve accurate 2D and 3D shape sensing using the fabricated WFBG array.

Main Methods:

• Fabrication of a WFBG array in MCF using a femtosecond-laser plane-by-plane technique.
• Introduction of an integrated modulation plane for simultaneous multi-core modulation.
• Optimization of inscription parameters (energy, grating order, modulation planes).
• Interrogation of the WFBG array using OFDR.

Main Results:

• Demonstration of a 60-cm-long WFBG array with 60 gratings.
• Achieved a fabrication speed of 35 seconds per WFBG with 10 modulation planes.
• Reported relative reconstruction errors of 1.41% in 2D and 1.95% in 3D shape sensing.

Conclusions:

• The developed WFBG array in MCF is suitable for high-accuracy shape sensing.
• The femtosecond-laser plane-by-plane technique offers an efficient method for WFBG fabrication.
• The integrated modulation plane simplifies the alignment process for multi-core inscription.