J.A. Tucknott

Strong photosensitive gratings in tin-doped phosphosilicate optical fibers

Strong photosensitive gratings of both type I and II have been demonstrated in germanium-free tin-doped phosphosilicate fibers. An index change of ~1.2 x 10(-3) has been achieved in 40 s of exposure. The fibers have strong absorption (~0.8 dB/microm) at the writing wavelength of ~248 nm because of tin doping. This is the f irst time to our knowledge that such strong gratings have been written in a phosphorous-containing silica fiber without low-temperature hydrogenation and that type II gratings have been written in a germanium-free fiber. The tin-doping technique can be used to write gratings in rare-earth-doped phosphosilicate fibers and to produce low-N.A. fibers for mass production of strong single-pulse type II gratings during fiber pulling.

High nonlinearity extruded single-mode holey optical fibers

We report the fabrication of the first microstructured single-mode non-silica glass fiber from an extruded preform. The measured effective nonlinearity (/spl gamma/) is 550 W/sup -1/ km/sup -1/, more than 500 times larger than standard silica fiber.

A dispersion tunable grating in a 10-Gb/s 100-220-km-step index fiber link

A dispersion tunable 40 mm fiber grating has been employed in a 10 Gb/s, step-index fiber link. Dispersion is effectively compensated for span lengths in the range 103-217 km. However, at the longer spans the increased dispersion of the grating results in a reduced bandwidth and therefore its center wavelength is found to be critical (/spl plusmn/0.005 nm).

Nanomechanical optical fiber.

Optical fibers are an excellent transmission medium for light and underpin the infrastructure of the Internet, but generally after fabrication their optical properties cannot be easily modified. Here, we explore the concept of nanomechanical optical fibers where, in addition to the fiber transmission capability, the internal core structure of the fiber can also be controlled through sub-micron mechanical movements. The nanomechanical functionality of such fibers is demonstrated in the form of dual core optical fibers, in which the cores are independently suspended within the fiber. The movement-based optical change is large compared with traditional electro-optical effects and we show that optical switching of light from one core to the other is achieved through moving one core by just 8 nm.

Holey fibers for nonlinear fiber devices

The wavelength-scale features in holey fibers lead to novel properties including endlessly single-mode guidance, high optical nonlinearity per unit length, and anomalous dispersion below 1.3µm. Such properties are useful for a wide range of nonlinear fiber devices.

Optical amplifiers and lasers in infrared fibres

We are currently investigating two infrared glasses for active applications. Gallium lanthanum sulphide (GLS) glass is investigated as a potential host material for rare-earth doped mid-infrared fiber lasers. We have fabricated gallium lanthanum sulphide glass by melt quenching and drawn it into fibers using the rod-in-tube technique. Fluoroaluminate glasses (ALF) are being prepared in planar form by spin coating and clad waveguides have been achieved. The quality of waveguides from both these materials is gradually being improved as methods to eliminate transition metals and other impurities, understand crystallization and reduce the imperfections at the core/clad interface are developed. Although initially motivated by the demand for a practical 1310 nm amplifier, interest has now extended further into the infrared. We describe recent progress in these glasses, their properties and applications.