Hydrogen-loaded fibers were exposed to solar radiation for 20 days, in which time the hydrogen was allowed to out-diffuse. Gratings written in these fibers show an increased photosensitivity compared with pristine fibers. Results show the solar radiation has a similar effect on both stripped and unstripped fibers. This work agrees with the fundamental process of using low fluence, long UV sources to photosensitize hydrogen-loaded, germanium-doped fibers.

Elliptically birefringent fibre has been fabricated by spinning the preform of a highly linearly birefringent photonic crystal fibre (PCF) during the drawing process. The resulting Spun Highly Birefringent (SHi-Bi) PCF offers intrinsic sensitivity to magnetic fields through the Faraday effect without the high inherent temperature sensitivities suffered by conventional spun stress birefringence fibres. The ellipticity of the birefringence has been measured and temperature independence has been demonstrated.

A double-pass photonic crystal fibre reference cell operating in reflection is demonstrated. The acetylene lines dependence with temperature (25°C to 140°C) are characterized. Coupling loss between single mode coupling fibres and the PCF is discussed.

A novel grating-writing interferometer is demonstrated. This interferometer is compact, stable, and tunable well over 1000 nm and does not suffer from the inherent path-length differences that are present in other methods. It allows for high-quality gratings to be inscribed by preventing light from unwanted orders from affecting the fringe pattern. This technique is used to introduce a novel method of apodization based on removing the Fresnel end reflections in a grating. The experimental evidence proves the concept and shows that the technique is potentially useful for Bragg-grating inscription.

A novel grating writing interferometer is demonstrated that is compact, stable, tuneable and introduces a new method of apodisation. It does not suffer from the inherent path length differences present in other techniques, making it amenable for low coherence sources and improves grating quality.

A novel grating writing interferometer is demonstrated using a phase mask to split the beam, an optical element to collimate the writing beams, and another phase mask to interfere the beams. This interferometer is compact, highly stable, tuneable and improves beam coherence making it amenable for writing with low coherence sources. It allows unwanted orders to be spatially filtered, improving the grating quality by removing the detrimental effect of allowing the zeroth order to impinge on the fibre. Results were achieved for spot gratings and long gratings that were made up of adjacent sub-gratings using a lens as the collimating element, and translated gratings using mirrors to collimate the beams. The fringe contrast evolution was examined, and a tuning range of over 50nm is demonstrated.

We show how a simple apodisation technique can be used to suppress side modes in fibre Bragg gratings. The technique recognises that these side modes arise from Fresnel reflections off the ends of the grating and can be reduced by simply tapering the dc-only component just beyond the ends of the grating. To this end the profile of the writing beams are altered using lens aberration, correspondingly smoothing the index modulation envelope and reducing reflections off the grating ends. This differs from conventional apodisation where the modulation depth of the induced refractive index is tapered appropriately.