Tim J. Ellingham

Quasi-lossless optical links for broad-band transmission and data processing

We present the first experimental implementation of a recently designed quasi-lossless fiber span with strongly reduced signal power excursion. The resulting fiber waveguide medium can be advantageously used both in lightwave communications and in all-optical nonlinear data processing.

Dual-pump Raman amplification with increased flatness using modulation instability

The application of modulation instability-initiated nonlinear broadening of two CW pumps at different wavelengths, in order to achieve superior gain ripple performance in broadband Raman amplifiers, is demonstrated for the first time experimentally. A particular example using Truewave and LEAF fibers is offered, in which the 0.1 dB gain ripple band is extended from 5 nm to 19 nm. Experimental results are in a good agreement with numerical modeling. Guidelines for optimal broadening are discussed.

Spectral modification of type IA fibre Bragg gratings by high-power near-infrared lasers

We report the first experimental measurements on the spectral modification of type IA fibre Bragg gratings, incorporated in an optical network, which result from the use of high-power, near-infrared lasers. The fibre grating properties are modified in a controlled manner by exploiting the characteristics of the inherent 1400 nm absorption band of the optical fibre, which grows in strength during the type IA grating inscription. If the fibre network is illuminated with a high-power laser, having an emission wavelength coincident with the absorption band, the type IA centre wavelength and chirp can be modified. Furthermore, partial grating erasure is demonstrated. This has serious implications when using type IA gratings in an optical network, as their spectrum can be modified using purely optical methods (no external heating source acts on the fibre), and to their long-term stability as the grating is shown to decay. Conversely, suitably stabilized gratings can be spectrally tailored, for tuning fibre lasers or edge filter modification in sensing applications, by purely optical means.

Spectral modification of type IA fibre Bragg gratings by high power near infra-red lasers

We report the first experimental measurements on the spectral modification of Type IA fibre Bragg gratings, incorporated in an optical network, which result from the use of high-power, near infrared lasers. The fibre grating properties are modified in a controlled manner by exploiting the characteristics of the inherent 1400nm absorption band of the optical fibre, which grows in strength during the Type IA grating inscription. If the fibre network is illuminated with a high power laser, having an emission wavelength coincident with the absorption band, the Type IA centre wavelength and chirp can be modified. Furthermore, partial grating erasure is demonstrated. This has serious implications when using Type IA gratings in an optical network, as their spectrum can be modified using purely optical methods (no external heating source acts on the fibre), and to their long-term stability as the grating is shown to decay. Conversely, suitably stabilised gratings can be spectrally tailored, for tuning fibre lasers or edge filter modification in sensing applications, by purely optical means.

Dual-pump Raman amplification with enhanced flatness using modulation instability

In this work, we utilize modulation instability to the broadening of the two CW-pumps of a wideband Raman amplifier. Applying nonlinear fiber process, we demonstrate a feasibility of a certain control over the broadening process, leading to clear improvements in the flatness of the amplifier gain over its operational bandwidth.

Design of a fiber scheme for nonlinear Raman pump broadening through modulation instability

In this work we explore numerically an experimentally the dependence of the broadened spectra on the choice of fibers and we analyze a series of basic rules to be taken into account when using nonlinear broadening to reduce the gain ripple of broadband Raman amplifiers

Wavelength tuning, chirping and thermally induced decay of type IA FBGs using purely optical methods

We report experimental measurements of reversible wavelength tuning, chirping and permanent thermally induced decay of type1A fibre Bragg gratings using purely optical means. The grating properties are modified in a controlled manner by utilising the characteristics of the intrinsic 1400nm absorption band of the optical fibre and two tuneable lasers coincident with that band. It is shown that the type 1A grating can be selectively tuned in a grating network and that selective tuning can be attained in a common section of suitably prepared optical fibre. Applications of this approach for tuning fibre lasers or edge filter modification in sensing applications are discussed.

CW Raman pump broadening using modulational instability

We examine theoretically and experimentally how the application of the modulation instability effect can be used to broaden CW Raman pump in order to achieve superior gain ripple performance in WDM transmission systems.