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A multi-wavelength channel distributed feedback laser diode array (DFB-LDA) for the low-cost and low-power consumption applications of WDM-based datacentre networks is reported. The gain spectrum and lasing wavelength of each channel are controlled by using selective area growth and E-beam lithography techniques, respectively. To reduce the operation current and parasitic capacitance of the proposed array, an etched mesa buried hetero-structure (EMBH) is introduced. From this study, it was found that an eight-channel 300 μm long λ/4-shifted DFB-LDA has a threshold current of 10 ± 1.5 mA and a side mode suppression ratio of over 50 dB at a current of 50 mA for all channels. A transmission test for this LDA showed a clear eye opening with a dynamic extinction ratio of over 4.5 dB at 10 Gb/s after a 2 km transmission.

Asymmetric 8-PSK with embedded BPSK for unequal error protection has been investigated theoretically. The BER performance is calculated and compared with that of symmetric MPSK with the same bandwidth efficiency. The results indicate that the asymmetric modulation scheme can be considered as a potential candidate for the transmission of two bit-streams with unequal error protection requirement.

An arbitrary L/M-fold image resizing method using lapped transforms is presented. The resizing operation is carried out in the lapped transform domain, by converting the images in the discrete cosine transform (DCT) domain into those in the lapped transform domain and vice versa. The proposed method provides visually fine images, while reducing the blocking effect to a very low level for images compressed at low bit rates.

A quadtree structured image coding method which avoids the blocking artefact without using postprocessing is discussed. Furthermore, the method improves the R-D performance considerably. Only a single pixel is encoded for each segmented block. Boundary interpolation and projective interpolation are applied for reconstruction using all adjacent encoded pixels.

Based on the equivalence between perceptrons and the conventional decision feedback equaliser, new classes of computationally efficient linear decision feedback equaliser and fuzzy adaptive equaliser are derived. A significantly reduced computational complexity can be achieved without performance degradation compared with that of existing fuzzy adaptive equalisers.

The polarisation characteristics of the radiator composed of a slot and a strip is presented. It is verified that the circularly-polarised waves or other forms of polarisation needed can be obtained by the radiator with some suitable choices of configuration.

A new learning method is proposed to enhance the performances of fuzzy adaptive resonance theory-predictive mapping (ARTMAP) neural networks in a noisy environment. It combines the average learning and slow learning for the weight vectors in fuzzy ARTMAP. It effectively reduces a category proliferation problem, and enhances recognition performance for noisy input patterns.

Trellis codes for frequency/phase modulation have larger asymptotic coding gain than trellis codes for phase modulation. Multilevel codes which enable multistage decoding have the advantage of larger asymptotic coding gain and lower decoder complexity than trellis codes. Combining these results, new two-level codes for frequency/phase modulation are presented.

Based on the fact that a decision feedback equaliser (DFE) can be divided into a linear equaliser and a prediction error filter with feedback, a new blind adaptation method for the DFE is proposed. The proposed method provides reliable convergence and the resulting symbol error rate is very close to that of the DFE using a training sequence

The authors propose an efficient memory allocation method for memory-constrained Huffman coding of multiple sources which employs the iterative bisection algorithm. The proposed method provides better performance over conventional allocation methods and can be applied to many adaptive variable-length coders with memory constraints.

A new rate-based scheduling discipline for packet switching networks is presented. The proposed algorithm remedies a drawback of the ‘virtual clock’ scheme, and provides a bandwidth guarantee like the ‘virtual clock’ scheme. The proposed scheme exhibits good properties comparable to the weighted fair queueing scheme even though it is still a simple algorithm.

A real time corona discharge imaging system is introduced, and the effect of the imaging parameters such as electric field intensities and their frequencies on the resulting images are investigated

We report experimental results which show that noncollinear surface-wave mixing on [111]-cut bismuth-germanium oxide can be used to realise an active, switchable directional coupler. For low-level inputs, the coupling is enhanced by as much as 20 dB by a semiconductor placed over the interaction region. The directivity is found to be greater than 40 dB.