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This study accessed the performance of the four-level Manchester coding (4-MC) and four-level modified Manchester (4-MM) technique at the bit rates of 20 and 40 Gb/s for the first-order and second-order optical equalisers. The performances were evaluated with respect to bit error rate (BER), power penalty, eye diagrams, and dispersion tolerance. Based on the results by utilising the second-order optical equaliser, at 20 Gb/s, the transmission distance of 4-MC and 4-MM was extended by 25 and 27 km of standard single-mode fibre (SSMF), respectively, while at the bit rate of 40 Gb/s, the 4-MC and 4-MM transmission distance was extended by 6.5 and 7.5 km of SSMF, respectively. Hence, the second-order optical equaliser can adequately compensate for the fibre dispersion and consequently the overall BER performance. Therefore, the proposed system could serve as an alternative to the next-generation high-speed optical transmission links.

The study presents theoretical and experimental investigations on radio over fibre links concerning the effect of fibre dispersion. An approach is presented to overcome the radio-frequency suppression effect in optical links based on the joint effect of semiconductor optical amplifier chirp, chromatic dispersion and non-linearities of optical fibre. The results show that the frequency notches caused by the dispersion induced carrier suppression effect may be sharply alleviated and the performance of the transmitted signal can be improved.

Generation of 100 GHz trains of 500-700 fs pulses using dual-frequency beat conversion in a step-like dispersion profiled fibre is reported. The authors believe that this is the first time the generation and compression of soliton pulses using such a fibre has been demonstrated. The fabrication of such fibre assemblies does not require any special facilities and relies only on conventional optical fibre technology. They believe that the use of profiling the fibre dispersion by fibre segments instead of continuously dispersion-decreasing fibre is not only possible but preferable in many applications.

Digital signal processing combined with either pre-distortion at the transmitter or coherent detection at the receiver can eliminate penalties due to fibre dispersion. The nonlinearity of transmission fibre results in an optimal balance of pre-distortion and receiver equalisation.

Future optical networks will employ many component technologies including transmitters, modulators, amplifiers, wavelength converters, add-drop multiplexers and crossconnects to provide flexible data provision at low cost. Fibre dispersion and nonlinear optical crosstalk become increasingly important as the overall capacity is increased and they constrain all aspects of the transmission strategy. By addressing the emerging component technologies the author reviews the context within which future dilute nitride semiconductor devices must operate.

Microwave photonic filtering is realised using a superstructured fibre Bragg grating. The time delay of the optical taps is precisely controlled by the grating characteristics and fibre dispersion. A bandpass response with a rejection level of >45 dB is achieved.

The dispersion slope of dispersion-shifted fibre has been successfully equalised by using a bend-induced positive dispersion slope in a singlemode fibre. We realised the bent fibre dispersion slope equaliser by using a 1.3 µm zero-dispersion pure silica core fibre (PSM). This equaliser provides a dispersion slope of –12.54 ps/nm2/km in the 1.5 µm region.

Optical millimetre-wave generation at 60 GHz using dual-mode semiconductor modelocked lasers is demonstrated. Dual-mode operation is achieved by mode selectivity of the chirped gratings. Suppression of signal distortion due to fibre dispersion is confirmed for generated millimetre waves.

Using direct measurement, the effect of macro-bending on the dispersion in dispersion compensating fibres was investigated. It was shown that even a relatively large bend radius of /spl sim/10 cm can modify the fibre dispersion in the range 1500-1600 nm.

It is shown by using numerical simulations that the carrier-suppressed-return-to-zero (CS-RZ) format has a wider dispersion tolerance relative to the conventional return-to-zero (RZ) format. Numerical simulations predict that the optimum fibre dispersion of the CS-RZ format should be zero and should stay near Ops/nm at a high fibre input power of 12 dBm in the L-band of a dispersion-shifted-fibre link. This robust dispersion characteristic against self-phase modulation was experimentally confirmed by a 40 Gbit/s 162 km transmission experiment.

Transmission of short pulses with suppressed third-order fibre dispersion effects is demonstrated by sinusoidal phase modulation of stretched optical pulses. Numerical simulation results show significantly less pulse distortion for transmission of 530 fs pulses over a 10 km fibre link achieved by applying 2.56 GHz phase modulation with a peak phase shift of 3π.

A simplified dispersion limit formula for IM/DD systems is derived to cover both positive and negative fibre dispersion coefficients. A simple method for calculating the dispersion limit of various singlemode fibres (conventional, dispersion-shifted or TrueWave, etc.) and for providing eye opening penalty evaluation of deployed systems is proposed.

By using dispersion-free single-mode fibres at 1.5 μm, where silica fibres have minimum loss, an optical transmission experiment was successfully carried out at 800 Mbit/s with 20 km repeater spacing. Error rate against receiving optical level characteristics showed that the optical power penalty caused by fibre dispersion is negligible after long line transmission at 1.5 μm.

It is shown with numerical examples that single-cladded, dispersion-shifted, single-mode fibres with arbitrary refractive-index profiles have spectral spot size and dispersion variations predictable from only two parameters. These are the Laplace spot-size value ?L and fibre dispersion value Mf specified at the wavelength ? = 1.55 ?m.