The authors report a wavelength tunable laser consisting of an in-line Fabry-Perot laser and lateral-grating assisted vertical codirectional coupled filter. The device can be tuned over 12 discrete 4 nm spaced longitudinal modes giving a total tuning range of 44 nm.

Eight/spl times/10 Gb/s WDM dispersion compensation is demonstrated using a single 1.3 metre long super step-chirped fibre grating with a continuous delay of 13.5 ns and bandwidth of 10 nm.

E-beam field writing strategies have been developed to reduce field stitching errors to nigligible levels. Applying these strategies, 40mm × 4mm grating structures have been written onto phase masks which have in turn been used to print gratings into photo-sensitive fibres. Transmission measurements from constant pitch gratings with uniform phase and single phase shifts as well as chirped gratings are reported.

For the first time, a simple technique is reported for apodising chirped or unchirped gratings of arbitrary length. Also reported for the first time is the fabrication and measurement of unapodised and apodised 100 mm long, step-chirped fibre gratings with a dispersion parameter of similar to 1.6ns-nm(-1) and a bandwidth of up to 0.75 nm. It is shown that long chirped gratings may be fabricated at predetermined wavelengths in standard telecommunications fibre for dispersion compensation.

Concatenation of apodised gratings to form a super-step-chirped fibre Bragg grating structure is demonstrated for the first time. Using this scheme, gratings of arbitrary lengths may be constructed for a predetermined wavelength span.

Simultaneous dispersion compensation for 4 wavelengths, each at 10 Gbs/sup -1/, is demonstrated over 125 km of optical fibre in the 1550 nm window using four 100 mm long step-chirped fibre gratings, apodised by a simple novel technique.

In this paper we show that a variety of band-pass filters may be fabricated with ease using simple replication of phase-shifted phase-masks, in germania and rare-earth doped fibres. it is shown that the band-pass may be located anywhere within the band-stop of the grating by adjusting the phase-mask prior to writing. Phase-steps have also been introduced by “trimming” with UV radiation, one half of the length of the grating. Preliminary experiments shown that higher reflectivity gratings should allow lasing in rare earth doped fibres

Fibre grating reflection filters with fully resolved extinctions greater than 64 dB and edge widths less than 1 nm have been fabricated in photosensitive optical fibres. Filters have been cascaded to give >74 dB of rejection.

There is currently worldwide interest in the theory and transmission of dark solitons for application in communications. Theoretical techniques have been proposed[1-3] for the generation of CW dark soliton pulse trains. One of them has been recently demonstrated recently [4]. The techniques rely on spectral filtering of a train of mode-locked pulses using both conventional phase and amplitude masks[l,5], or on the adiabatic transformation of a beat frequency from two lasers[3,4], A third approach[2] is based on the direct modulation of a CW signal from a DFB laser. In another technique, a chirped fibre grating was used to provide the correct sign of dispersion in a Pr:ZBLAN fibre laser to generate dark pulses[6]. In the spectral filtration technique, the frequency content of mode-locked pulses is first spatially dispersed and this allows for the alteration of the amplitude and phases of the spectral components in the Fourier plane[1]. The Fourier transform of the filtered spectrum generates the dark pulse train. These techniques are generally more suitable for the generation of ultra high repetition rate dark pulse train since it is easier to filter larger bandwidths.

Reflection grating structures have been replicated in photosensitive optical fibres using phase shifted phase masks for the first time. The sensitivity of the narrow bandpass peak to alignment and position of the phase shift are reported.<>