Spi Lasers UK Limited

Andy Piper

David Neil Payne

Michael Kevan Durkin

Mikhail Nickolaos Zervas

Fabio Ghiringhelli

Jayanta Kumar Sahu

Stephen Roy Norman

Louise Mary Brendan Hickey

Andrew Michael Gillooly

In one embodiment, a photo-darkening resistant optical fiber includes a waveguide having a numerical aperture less than 0.15. The waveguide includes a core having a refractive index nand a pedestal having a refractive index n, and wherein the fiber includes a first cladding having a refractive index nsurrounding the pedestal, wherein nis greater than n, nis greater than n. The core includes silica, a concentration of alumina of between approximately 0.3 to 0.8 mole percent, a concentration of phosphate of substantially 15 mole percent, a concentration of ytterbium substantially in the range 20000 to 45000 ppm. The pedestal can include silica, phosphate and germania. The core can have substantially zero thulium dopant.

Apparatus for providing optical radiation

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Southampton, United Kingdom

Andy Piper