Showing papers in "Electronics Letters in 2000"
TL;DR: Experimental results clearly indicate that this metric reflects the quality of visual information obtained from the fusion of input images and can be used to compare the performance of different image fusion algorithms.
Abstract: A measure for objectively assessing the pixel level fusion performance is defined. The proposed metric reflects the quality of visual information obtained from the fusion of input images and can be used to compare the performance of different image fusion algorithms. Experimental results clearly indicate that this metric is perceptually meaningful.
1,446 citations
TL;DR: In this article, the fundamental working equations required to describe the associated power transfer are derived and the application of this geometry to a variety of optical phenomena including add/dropping of optical beams, add/drop filtering and optical power switching are discussed.
Abstract: The most basic and generic configuration, which consists of a unidirectional coupling between a ring resonator and a waveguide, is considered. The fundamental working equations required to describe the associated power transfer are derived and the application of this geometry to a variety of optical phenomena is discussed. These phenomena include 'add/dropping' of optical beams, add/drop filtering and optical power switching.
1,108 citations
TL;DR: In this article, a single wavelength channel, optical time division multiplexed and polarisation multiplexing 128 Tbit/s signal has been successfully transmitted over 70 km Third and fourth-order simultaneous dispersion compensation was used with a 10 GHz synchronous phase modulator.
Abstract: A single wavelength channel, optical time division multiplexed and polarisation multiplexed 128 Tbit/s signal has been successfully transmitted over 70 km Third- and fourth-order simultaneous dispersion compensation was used with a 10 GHz synchronous phase modulator The input pulse width was 380 fs, and the transmitted pulsewidth was 400 fs All 128 channels demultiplexed to 10 Gbit/s had a bit error rate of less than 1/spl times/10/sup -9/
351 citations
TL;DR: Simulations using the 1MT-2000/3GPP parameters demonstrate that this method gives /spl sim/0.2 to 0.4 dB performance gain compared to the standard max-log-MAP algorithm.
Abstract: Decoding turbo codes with the max-log-MAP algorithm is a good compromise between performance and complexity. The decoding quality of the max-log-MAP decoder is improved by using a scaling factor within the extrinsic calculation. Simulations using the 1MT-2000/3GPP parameters demonstrate that this method gives /spl sim/0.2 to 0.4 dB performance gain compared to the standard max-log-MAP algorithm.
294 citations
TL;DR: In this paper, an InP-InGaAs uni-travelling-carrier photodiode with a 3 dB bandwidth of 310 GHz and a FWHM of 0.97ps was fabricated.
Abstract: The authors have fabricated an InP-InGaAs uni-travelling-carrier photodiode that exhibits a 3 dB bandwidth of 310 GHz and a pulse width (FWHM) of 0.97ps. Both of which are record values for photodetectors operating at a wavelength of 1.55 /spl mu/m. The average electron velocity in the depletion region is estimated to be 3.0/spl times/10/sup 7/ cm/s.
289 citations
TL;DR: In this article, the authors used two n-type As/GaAs distributed Bragg reflectors with a selectively oxidized current aperture adjacent to the optical cavity, and the top output mirror contains a tunnel junction to inject holes into the active region.
Abstract: Selectively oxidized vertical cavity lasers emitting at 1294 nm using InGaAsN quantum wells are reported for the first time which operate continuous wave at and above room temperature. The lasers employ two n-type Al{sub 0.94}Ga{sub 0.06}As/GaAs distributed Bragg reflectors each with a selectively oxidized current aperture adjacent to the optical cavity, and the top output mirror contains a tunnel junction to inject holes into the active region. Continuous wave single mode lasing is observed up to 55 C. These lasers exhibit the longest wavelength reported to date for vertical cavity surface emitting lasers grown on GaAs substrates.
288 citations
TL;DR: The authors present a method for deriving the bounds on the correlation of a polyphase sequence set concerning the size, length and low or zero correlation zone based on Welch's technique.
Abstract: To eliminate multiple access interference, approximately synchronised code division multiple access systems employ spreading sequence sets with low or zero correlation zone properties. The authors present a method for deriving the bounds on the correlation of a polyphase sequence set concerning the size, length and low or zero correlation zone based on Welch's technique.
262 citations
TL;DR: In this paper, the first non-silica holey or microstructured optical fiber was reported, and the chalcogenide glass gallium lanthanum sulphide was used.
Abstract: The fabrication of the first non-silica holey or microstructured optical fibre is reported. The chalcogenide glass gallium lanthanum sulphide was used. Applications of such fibres include optical switching, high power-delivery, acousto-optic devices, air-guiding fibres, fibre sensors, mid-IR devices, amongst others. In addition, holey fibre technology provides an improved route towards fabricating singlemode compound glass fibres
260 citations
TL;DR: It is shown that degenerate channels, called 'keyholes', may arise under realistic assumptions which have zero correlation between the entries of the channel matrix H and yet only a single degree of freedom.
Abstract: Multi-element system capacities are usually thought of as limited only by correlations between elements. It is shown that degenerate channels, called 'keyholes', may arise under realistic assumptions which have zero correlation between the entries of the channel matrix H and yet only a single degree of freedom.
252 citations
TL;DR: In this paper, the authors proposed a new charge pump circuit with perfect current matching characteristics in a 0.25 /spl mu/m CMOS process with an error amplifier and reference current sources.
Abstract: Conventional CMOS charge pump circuits have some current mismatching characteristics. The current mismatch of the charge pump in the PLLs generates a phase offset, which increases spurs in the PLL output signals. In particular, it reduces the locking range in wide range PLLs with a dual loop scheme. A new charge pump circuit with perfect current matching characteristics is proposed. By using an error amplifier and reference current sources, one can achieve a charge pump with good current matching characteristics. It shows nearly perfect current matching characteristics over the whole VCO input range, and the amount of the reference spur is <-75 dBc in the PLL output signal. The charge pump circuit is implemented in a 0.25 /spl mu/m CMOS process.
235 citations
TL;DR: In this paper, a pulsed lasing at 1.3 /spl mu/m via the exciton ground state was demonstrated for vertical cavity surface emitting lasers containing three uncoupled sheets of InAs quantum dot active layers.
Abstract: Pulsed lasing at 1.3 /spl mu/m via the exciton ground state is demonstrated for vertical cavity surface emitting lasers containing three uncoupled sheets of InAs quantum dot active layers. The structures are grown directly on GaAs substrates and when fabricated include selectively oxidised AlO current apertures, intracavity metal contacts, and AlO/GaAs distributed Bragg reflectors. Experimental devices operate pulsed at room temperature with threshold currents below 2 mA and differential slope efficiencies above 40%.
TL;DR: More than 1000 optical frequency channels were generated with 12.5 GHz spacing from a single supercontinuum source in this article, and 600-700 channels for the wavelength range 1512-1580 nm were confirmed to offer SNRs and Q factors sufficient for multi-span 2.5 Gbit/s DWDM transmission.
Abstract: More than 1000 optical frequency channels are generated with 12.5 GHz spacing from a single supercontinuum source. 600–700 channels for the wavelength range 1512–1580 nm are confirmed to offer SNRs and Q factors sufficient for multi-span 2.5 Gbit/s DWDM transmission.
TL;DR: In this paper, a Rayleigh backscatter based fiber optic strain sensor using a time division multiplexing scheme with an optical pulse was presented, which has a gauge length of < 0.5 m and a strain sensitivity of < 1 n/spl epsiv///spl radic/Hz at 2 kHz.
Abstract: A fibre optic strain sensor based on Rayleigh backscatter using a time division multiplexing scheme with an optical pulse is presented. The sensor has a gauge length of <0.5 m and a strain sensitivity of <1 n/spl epsiv///spl radic/Hz at 2 kHz.
TL;DR: In this article, a simple analytical expression for the current flow in a diode driven by a voltage source through a series resistance is presented, based on the Lambert W-function.
Abstract: A simple analytical expression is presented for the current flow in a diode driven by a voltage source through a series resistance. The proposed solution is based on the Lambert W-function. The new expression leads to an efficient method for extracting series resistance from measured current-voltage data. Experimental results are presented which validate the proposed solution and extraction method.
TL;DR: In this paper, an enhancement mode AlGaN/GaN heterojunction field-effect transistor (HFET) with selectivity grown pn junction gate is presented, which enables both depletion and enhancement mode HFETs to be fabricated on the same wafer.
Abstract: A report is presented into the fabrication and characterisation of an enhancement mode AlGaN/GaN heterojunction field-effect transistor (HFET) with selectivity grown pn junction gate. At zero gate bias the device channel is depleted due to the high built-in potential of the gate-channel junction. The selective area growth approach enables both depletion and enhancement mode HFETs to be fabricated on the same wafer thus opening up the possibility of designing high speed, low consumption GaN-based logical integrated circuits.
TL;DR: In this article, the authors presented analytical formulas to describe the shift in the resonance wavelength of a long-period fiber grating in response to etching of the fiber cladding or a change in the external refractive index.
Abstract: Analytical formulas are presented for the first time to describe the shift in the resonance wavelength of a long-period fibre grating (LPFG) in response to etching of the fibre cladding or a change in the external refractive index. The accuracy of the formulas is confirmed by comparison with numerical simulations and experimental results. It is shown that the resonance wavelengths of an etched LPFG are more sensitive to the external refractive index than those of an unetched grating.
TL;DR: A new type of proxy signature scheme is presented called the proxy multi-signature scheme in which a proxy signer can generate a proxy signature on behalf of two or more original signers.
Abstract: Proxy signature schemes allow a proxy signer to generate a proxy signature on behalf of an original signer. However, since in previous proxy signature schemes a proxy signature is created on behalf of only one original signer, these schemes are referred to as proxy mono-signature schemes. A new type of proxy signature scheme is presented called the proxy multi-signature scheme in which a proxy signer can generate a proxy signature on behalf of two or more original signers.
TL;DR: The results of optical logic exclusive-OR (XOR) at up to 20 Gbit/s in an integrated SOA-based Mach-Zehnder interferometer are presented and BER measurements are demonstrated for the first time.
Abstract: The results of optical logic exclusive-OR (XOR) at up to 20 Gbit/s in an integrated SOA-based Mach-Zehnder interferometer are presented. For the first time, to the knowledge of the authors, BER measurements are demonstrated on 10 Gbit/s optical logic XOR, with zero penalty. In addition. For the first time 20 Gbit/s all-optical XOR, with an integrated device that allows simple, stable, and efficient operation, is demonstrated.
TL;DR: Soliton effects are observed at 850 nm in a pure silica photonic crystal fiber with group velocity dispersion (GVD) characteristics unattainable in conventional fibre as mentioned in this paper. But this is not the case in the case of optical fiber.
Abstract: Soliton effects are observed at 850 nm in a pure silica photonic crystal fibre with group velocity dispersion (GVD) characteristics unattainable in conventional fibre. Zero GVD is obtained at 740 nm.
TL;DR: A threshold current of 40 /spl mu/A, nearly 1/4 of the previous lowest record, has been obtained in a GaInAsP-InP microdisk injection laser as discussed by the authors.
Abstract: A threshold current of 40 /spl mu/A, nearly 1/4 of the previous lowest record, has been obtained in a GaInAsP-InP microdisk injection laser. This decrease was thought to be mainly due to the reduction of disk diameter and symmetric post-claddings by Cl/sub 2//Xe inductively coupled plasma etching.
TL;DR: In this paper, an efficient algorithm for robust whitening in the presence of temporally uncorrelated additive noise that may be spatially correlated is presented, which consists in the eigenvalue decomposition of a positive definite linear combination of a set a correlation matrices taken at nonzero lags.
Abstract: An efficient algorithm is presented for robust whitening in the presence of temporally uncorrelated additive noise that may be spatially correlated. This whitening is introduced as a pre-processing step in the blind source separation process. The robust whitening consists in the eigenvalue decomposition of a positive definite linear combination of a set a correlation matrices taken at nonzero lags. The coefficients of the linear combination are computed by a finite step global convergence algorithm. Some numerical simulations are provided to illustrate the effectiveness of the solution.
TL;DR: In this paper, the first measurements of curvature made using Bragg gratings written in separate cores of a multicore optical fiber are described, where the gratings act as independent, but isothermal, strain gauges.
Abstract: The first measurements of curvature made using Bragg gratings written in separate cores of a multicore optical fibre are described. The gratings act as independent, but isothermal, strain gauges. The difference in Bragg wavelength between the gratings provides a temperature-independent measurement of the local curvature.
TL;DR: An interleaver-based technique for improving the peak-to-average power ratio (PAP) of an orthogonal frequency division multiplexing signal is presented in this article.
Abstract: An interleaver-based technique for improving the peak-to-average power ratio (PAP) of an orthogonal frequency division multiplexing signal is presented. For this technique, K-1 random interleavers are used to produce (K-1) permuted sequences from the same information sequence. The PAPs of the permuted sequences and the original information sequence are then computed using K oversampled fast Fourier transforms (OFFTs). The sequence with the lowest PAP is chosen for transmission. Results show that for 256 subcarriers and quadrature phase shift keying data symbols, even with K=2, the 0.1% PAP is reduced by 1.3 dB and with K=4 it is reduced by 2 dB. The 0.1% PAP can be reduced by 3 dB and the 0.01% PAP by 4 dB at a cost of 16 OFFTs and a data rate loss of <0.8% with K=16.
TL;DR: In this article, the authors introduce a method of implementing any arbitrary impedance, using a digital signal processor, on a resonant simply supported beam using a PZT transducer.
Abstract: Piezoelectric transducer (PZT) patches may be attached to structures to reduce vibration. The PZT patches essentially convert vibrational mechanical energy to electrical energy. The electrical energy can be dissipated via an electrical impedance. The authors introduce a method of implementing any arbitrary impedance, using a digital signal processor. The ‘synthetic impedance’ is demonstrated on a resonant simply supported beam.
TL;DR: In this article, a near-IR femtosecond laser was used to directly write a 1 cm long optical waveguide in Nd-doped silicate glass, achieving a gain of 1.5 dB/cm at a signal wavelength of 1054 nm.
Abstract: A near-IR (775 nm) femtosecond laser has been used to directly write a 1 cm long optical waveguide in Nd-doped silicate glass. A gain of 1.5 dB/cm was obtained at a signal wavelength of 1054 nm for /spl sim/346 mW of 514 nm pump power, in front of the input coupling objective.
TL;DR: In this paper, an adaptive partial transmit sequence (PTS) technique is presented for the reduction of the peak-to-average power ratio (PAP) of an orthogonal frequency division multiplexing (OFDM) signal.
Abstract: An adaptive partial transmit sequence (PTS) technique is presented for the reduction of the peak-to-average power ratio (PAP) of an orthogonal frequency division multiplexing (OFDM) signal. The main problem for PTS is how to minimise the number of iterations necessary for locating the optimal weighting factors (which increases exponentially with the number of sub-blocks). In the proposed adaptive PTS approach, the iterations are stopped once the PAP drops below a preset threshold. For an OFDM system with 256 subcarriers and QPSK data symbols, adaptive PTS reduces the 0.1% PAP by 4 dB, while PTS (non-adaptive) reduces it by 4.1 dB. The complexity of adaptive PTS is just 2% of that of PTS.
TL;DR: A generalised sphere decoding algorithm has the maximum likelihood performance for both the uplink and downlink with moderate complexity in its application to the detection of information symbols in a multiantenna cellular system.
Abstract: A generalised sphere decoding (GSD) algorithm is presented. Its application to the detection of information symbols in a multiantenna cellular system with N antennas at the mobile and M/spl ges/N antennas at the base station is explored. The GSD algorithm has the maximum likelihood (ML) performance for both the uplink and downlink with moderate complexity.
TL;DR: A new voice activity detection (VAD) algorithm is proposed for estimating the spectrum of car noise in which noise is filtered out in the frequency domain, which can prevent incorrect detections caused by unvoiced or nasal sounds with high frequency components being covered by car noise with low frequency components.
Abstract: A new voice activity detection (VAD) algorithm is proposed for estimating the spectrum of car noise in which noise is filtered out in the frequency domain. The proposed algorithm uses the log energy parameters which are composed of two parts in the critical band. The algorithm detects the noise period by applying two adaptive thresholds to each part. Using the noise period we can reliably estimate the time-varying noise characteristics. The advantage of the proposed technique is that it can prevent incorrect detections caused by unvoiced or nasal sounds with high frequency components being covered by car noise with low frequency components. The algorithm is suitable for real time implementation with one microphone. Also, a speaker independent speech recognition system has been implemented for car navigation using a fixed point Oak DSP system, which incorporates the proposed VAD algorithm. The system enhanced the recognition rates for 12 isolated command words to 94.52%, compared with the 80.7% of the baseline recogniser.
TL;DR: In this paper, the authors report all-optical 100 Gbit/s wavelength conversion employing cross-phase modulation for the first time, and they use a cross-photon-based modulation scheme.
Abstract: The authors report all-optical 100 Gbit/s wavelength conversion employing cross-phase modulation for the first time
TL;DR: The practicability of using phase modulation in a 16 channel 10 Gbit/s system over 1600 km of standard SMF with simple dispersion compensation and the robustness in presence of ASK modulated channels has been shown for the first time.
Abstract: The practicability of using phase modulation in a 16 channel 10 Gbit/s system over 1600 km of standard SMF with simple dispersion compensation and the robustness in presence of ASK modulated channels has been shown for the first time.