All-fibre Bragg grating filters and lasers for future optical networks

Abstract

Bragg gratings in optical fibre waveguides have now been around for 25 years and they were soon after being realised, identified as one of the most significant fibre-optic inventions with potentials in a wide variety of areas among telecommunications equivalent to that of the erbium doped fibre amplifier. Following their creation a plurality of in-fibre functions were thought possible with low or no insertion-loss. Although fabrication and control of vital grating parameters was limited in the early stages of their life, initially a number of filtering functions were identified for obvious demonstrations. It soon became apparent though that not just standard filtering manipulation was possible. Identifying the true potential of the devices has let to considerable effort being concentrated on their full exploitation implying building an infrastructure supported by theoretical design and manufacturing techniques around them. These techniques combined have let to a scenario where currently it is the imagination more than the actual design and manufacturing capabilities that imposes a limitation to what is being demonstrated and now they find applications in most of the modern telecommunications network.
Cladding-pumped fibre technology has revolutionised fibre lasers over the last decade, increasing output power from less than 1 W with traditional core-pumping to well over 100 W. Even 1 kW of power has been reached in multi-mode designs, when several devices have been arranged in series or in parallel. For output powers below 100W, a few diode bars or multi-emitter laser diode assemblies are adequate pump sources. However, for powers beyond the 100 W level, diode stacks seem to be a better choice. The increasing availability of suitable diode stacks and the possibility of efficient fibre launch make them very attractive for pumping of high-power fibre-lasers. At the same time, while fibres proved very reliable at powers up to ~100 W, it is clear that further power-scaling to the kW level with diode stack pumping requires significant fibre optimisation in terms of fibre composition, pump coupling, and/or overall device layout. This is especially true when a single-mode output is required. We will in this presentation discuss and highlight some of the most recent advances in Bragg grating devices and applications in advanced components together with the most recent advances in the area of high power fibre lasers. In particular we will show examples of the latest in Bragg gratings for dispersion-control, short pulse-manipulation, advanced filtering applications together with some of our 1kW and speculate into what the future holds for Bragg gratings and high-power lasers and amplifiers.

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Identifiers

ORCID for J. Nilsson: orcid.org/0000-0003-1691-7959

ORCID for J.K. Sahu: orcid.org/0000-0003-3560-6152

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