Writing Bragg Gratings in Multicore Fibers

Area of Science:

• Optics and Photonics
• Materials Science

Background:

• Fiber Bragg gratings (FBGs) are essential components for compact and robust filters in diverse applications, including astronomy.
• Achieving strong single-wavelength suppression in multicore fibers necessitates uniform transmission profiles across all cores.
• Conventional FBG inscription methods are unsuitable for multicore fibers due to cladding-induced UV laser beam distortion.

Purpose of the Study:

• To address the challenge of inscribing uniform FBGs in multicore fibers.
• To present a novel technique for improving core-to-core uniformity during FBG fabrication in multicore fibers.

Main Methods:

• A specialized optical element, a flat-sided glass capillary tube, was employed during UV laser inscription.
• The capillary tube was positioned over the multicore fiber section to maintain the UV laser beam's dimensions.
• This method ensures consistent beam exposure across all fiber cores.

Main Results:

• Significant improvements in core-to-core uniformity were demonstrated for a 7-core fiber.
• The developed technique effectively mitigated UV laser beam distortion caused by the multicore fiber's curved cladding.
• Consistent transmission profiles were achieved across the fiber cores.

Conclusions:

• The novel inscription method using a capillary tube is highly effective for producing uniform FBGs in multicore fibers.
• This technique offers a viable solution for fabricating advanced optical filters for research and commercial applications.
• The method is scalable and can be applied to larger multicore fiber structures.