Zero total dispersion in graded-index single-mode fibres

The combined effects of composite material dispersion, profile and waveguide dispersion can be made zero at a wavelength which depends on core diameter, refractive-index profile and composition. Wide bandwidths over large repeater spacings are therefore possible although close fabrication tolerances may be required.     

Phase-shifted Moire grating fibre resonators

A novel technique for fabricating fibre grating resonators is reported. Using this technique, a resonant filter response with a bandwidth of 0.04 nm ( approximately 5 GHz) centred at 1535.1 nm and with a finesse of 20 has been obtained.<>     

Birefringence in optical fibres with elliptical cross-section

A comparison is made between various approximations for the phase delay between orthogonally polarised modes in elliptical optical fibres. A more accurate analysis is presented which gives a lower value for the birefringence produced by a given ellipticity. The effect on fibre bandwidth is shown to be small compared with that resulting from stress birefringence.     

Zero-mode dispersion in single-mode fibres

Near cutoff the loss of the LP11-mode in cladded optical fibres becomes very high in the presence of even slight bends. Singlemode operation can thus be achieved with zero-mode dispersion as well as zero material dispersion, thus promising enormously large bandwidths.     

Integrated laser and add-drop optical multiplexer for narrowband wavelength division multiplexing

The fabrication and characterisation of a monolithically integrated narrowband add-drop multiplexer and DBR laser are reported. Multiplexer bandwidth of 2-3.5 nm have been measured with a Bragg extinction ratio >23 dB.<>     

Integrated three channel laser and optical multiplexer fornarrowband wavelength division multiplexing

The fabrication and characterisation of a monolithically integrated three channel narrowband wavelength multiplexer and DBR laser are reported. The multiplexers include Bragg gratings with an extinction ratio of >20 dB and a bandwidth of ~1 nm to give channel spacings of <10 nm     

Narrowband fiber grating filters

Two techniques for the fabrication of fiber gratings with a narrowband filter response are reported. In the first technique, the reflection bandwidth is reduced by increasing the grating length. Fiber gratings 10 mm long have been made with a bandwidth of ~0.3 nm. In the second technique, a phase shift is incorporated into the grating to form a resonant structure. Fiber resonators with resonant dips in reflection and peaks in transmission having full-width half-maximum (FWHM) bandwidths of ~0.08 nm have been fabricated. A corresponding narrowband transmission peak was also measured     

Field deformation in a curved single-mode fibre

Simple formulae are given for the field displacement caused by bending, the change in mode volume and for the mode coupling loss which arises at transitions between straight and curved sections of single-mode optical fibre. These formulae are in good agreement with other, more exact, theories.