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DIRECTED ENERGY PROFESSIONAL SOCIETY

Abstract: 24-Symp-201

UNCLASSIFIED, PUBLIC RELEASE

High-Efficiency Hollow Core Fiber Delivery Modules

Abstract
Directed energy (DE) systems are rapidly being realized in real-world operational environments. Reliable, robust and efficient beam delivery of individual multi-kW class lasers to remote beam directors and combiners will be a key enabler. Use of free space optics delivery limits flexibility, reduces robustness, and adds substantial cost and SWAP to directed energy systems. Fiber delivery is an ideal alternative, but conventional single mode and large mode area (LMA) fiber technology is limited by nonlinear effects when lengths are more than several meters.
Hollow Core (HC) fiber technology is an ideal solution. Industrial applications are already pushing the fiber technology. Anti-Resonant, or negative curvature, fibers (AR-HC) are capable of delivering kW level powers with low loss (30.0 dB/m) and minimal nonlinearity.
HC fibers mitigate the challenges associated with LMA fibers and will enable installation in situations where fiber bending is severe and long lengths of fibers are required. Current state of the art demonstrations have shown that these fibers are able to handle the power demands, but the missing link is sealing the fiber end face for use in field based environments. The work done by NKT Photonics uses next generation HC fibers and advanced fiber termination methods to create compact components suitable for fielded DE applications.
NKTP has developed a process to terminate HC fiber for high power applications. In order to protect the HC fiber from environment contamination and degradation, this end-capped assembly provides a hermetic seal on the ends of the fiber. This termination can be integrated into a multi-kW fiber-to-fiber coupling module for high power application and fiber delivery.
Current development at NKTP utilizes a nested anti-resonant node-less fiber (NANF) with an attenuation of 0.5 dB/km in the wavelength region of 1060 nm. Recent development efforts by NKT Photonics have achieved >92% coupling efficiency through >10 meters of terminated fiber at 1.3 kW of input power with negligible degradation to transmission and beam quality at the output of the fiber.

UNCLASSIFIED, PUBLIC RELEASE