Showing papers in "Electronics Letters in 1994"
TL;DR: In this paper, a block coding scheme for the reduction of the peak to mean envelope power ratio of multicarrier transmission schemes such as OFDM was proposed, and the specific example of a four-carrier signal was shown that the peak-to-means-envelope power ratio can be reduced from 6.02 dB to 2.48 dB with a 3/4 rate block code.
Abstract: A block coding scheme for the reduction of the peak to mean envelope power ratio of multicarrier transmission schemes such as OFDM is proposed. The principle of the scheme is illustrated with the specific example of a four-carrier signal. It is shown that the peak to mean envelope power ratio of this signal can be reduced from 6.02 dB to 2.48 dB with a 3/4 rate block code. The application of the block coding principle with flexibility such that the coding rate can be traded against peak to mean envelope power ratio is illustrated with the example of an eight-carrier signal.
804 citations
TL;DR: In this article, a low threshold, large T/sub o/ injection laser emission via zero-dimensional states in (InGa)As quantum dots is demonstrated, which are formed due to a morphological transformation of a pseudomorphic In/sub 0.5/Ga/sub0.5 /As layer.
Abstract: Low threshold, large T/sub o/ injection laser emission via zero-dimensional states in (InGa)As quantum dots is demonstrated. The dots are formed due to a morphological transformation of a pseudomorphic In/sub 0.5/Ga/sub 0.5/As layer. Laser diodes are fabricated with a shallow mesa stripe geometry.<
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734 citations
TL;DR: In this paper, the spectral properties of two superimposed fiber gratings having different Bragg wavelengths (850 and 1300 nm) with respect to strain and temperature were studied, and it was shown that the ratio of sensitivity at two Bragg wavelength is dependent on strain, which can be used for simultaneous measurement of these parameters.
Abstract: The spectral behaviour of two superimposed fibre gratings having different Bragg wavelengths (850 and 1300 nm) with respect to strain and temperature has been studied. The results show that the ratio of sensitivity at two Bragg wavelengths is dependent on strain and temperature, which can be used for simultaneous measurement of these parameters using a single sensing element.
560 citations
TL;DR: In this article, a vertical-cavity surface emitting laser fabricated using selective oxidation to form a current aperture under a top monolithic distributed Bragg reflector mirror is reported.
Abstract: Novel vertical-cavity surface emitting lasers fabricated using selective oxidation to form a current aperture under a top monolithic distributed Bragg reflector mirror are reported. Large cross-sectional area lasers (259 µm2) exhibit threshold current densities of 150 A/cm2 per quantum well and record low threshold voltage of 1.33 V. Smaller lasers (36 µm2) possess threshold currents of 900 µA with maximum output powers greater than 1 mW. The record performance of these oxidised vertical-cavity lasers arises from the low mirror series resistance and very efficient current injection into the active region.
349 citations
TL;DR: In this paper, a 40 mm long optical fiber grating superstructure is written by translating an ultraviolet writing beam along a fiber and phase mask assembly while its intensity is periodically varied, and the grating reflects at multiple wavelengths, equally spaced by 0.13 nm.
Abstract: A 40 mm long optical fibre grating superstructure is written by translating an ultraviolet writing beam along a fibre and phase-mask assembly while its intensity is periodically varied. The grating reflects at multiple wavelengths, equally spaced by 0.13 nm, over a range of more than 1.0 nm. This grating structure has applications in signal processing and tunable fibre lasers.<
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275 citations
TL;DR: In this paper, a harmonically and regeneratively modelocked erbium fiber ring laser at 1.55 mu m for the first time was reported. But this was achieved with a high speed photodetector and a high Q dielectric filter.
Abstract: The authors report the operation of a harmonically and regeneratively modelocked erbium fibre ring laser at 1.55 mu m for the first time. Harmonic regenerative modelocking was achieved by feeding back the harmonic longitudinal beat signal which was detected with a high speed photodetector and a high Q dielectric filter. The repetition rate was 10 GHz and the soliton effect shortened-the pulse width from 7.0 to 2.7 ps.
249 citations
TL;DR: In this article, a simple all optical fiber wavelength shift detection scheme for use with fiber Bragg grating sensing systems is described, based on the use of a wavelength division coupler designed to exhibit a monotonic dependence of the splitting ratio on wavelength over a 50 nm range.
Abstract: A simple all optical fibre wavelength shift detection scheme, for use with fibre Bragg grating sensing systems, is described. The system is based on the use of a wavelength division coupler designed to exhibit a monotonic dependence of the splitting ratio on wavelength over a 50 nm range.
248 citations
TL;DR: In this paper, the authors present a microstrip antenna with a dielectric substrate and a height varying between lambda /20 and lambda /100, at which the "folded dipole" adaptation techniques are not applicable.
Abstract: In reply to the Comment (given by Burbery, R.A., Elect., Lett., vol., p. 745, 1994) we wish to say: (i) Our antenna is a microstrip antenna with a dielectric substrate and a height varying between lambda /20 and lambda /100. At such heights the 'folded dipole' adaptation techniques are not applicable. >
246 citations
TL;DR: In this article, an electro-optical oscillator capable of generating high stability optical signals at frequencies up to 70 GHz was described, and a comb of stable frequencies was produced by modelocking the oscillator.
Abstract: The authors describe an electro-optical oscillator capable of generating high stability optical signals at frequencies up to 70 GHz. Signals as high as 9.2 GHz were generated with an optical wavelength of 1310 nm using the oscillator, and a comb of stable frequencies was produced by modelocking the oscillator. >
226 citations
TL;DR: In this article, an adaptive equaliser for polarisation mode dispersion (PMD) is developed, and its performance is evaluated in a 10 Gbit/s transmission system.
Abstract: An adaptive equaliser for polarisation mode dispersion (PMD) is developed, and its performance is evaluated in a 10 Gbit/s transmission system. This equaliser suppresses the power penalty due to PMD from 6.9 to 1.0 dB for a PMD value up to 65.7 ps. This result suggests the possibility of PMD compensation in multigigabit, 10000 km transmission systems.
222 citations
TL;DR: In this paper, an inline photolytic grating has been used to construct a pi-phase-shifted distributed phase structure in an optical fiber with a transmission filter of approximately 100 MHz.
Abstract: UV post-processing of an inline photolytic grating has allowed the fabrication of a pi -phase-shifted distributed phase structure in an optical fibre with a transmission filter of approximately 100 MHz.
TL;DR: A novel, efficient, self-normalising, unsupervised adaptive learning algorithm for the on-line (real-time) separation of statistically independent unknown source signals from a linear mixture of them.
Abstract: The authors present a novel, efficient, self-normalising, unsupervised adaptive learning algorithm for the on-line (real-time) separation of statistically independent unknown source signals from a linear mixture of them. In contrast to the known algorithms the new algorithm allows the separation (or extraction) of extremely badly scaled signals (i.e. some or even all of the source and/or sensor signals can be very weak). Moreover, the mixing matrix can be very ill-conditioned. >
TL;DR: An incoherent optical code division multiple access (CDMA) concept using a combination of wavelength hopping and time spreading is introduced employing prime-hop sequences, which feature an autocorrelation function with zero sidelobes and crosscorrelation function of at most 1.
Abstract: An incoherent optical code division multiple access (CDMA) concept using a combination of wavelength hopping and time spreading is introduced employing prime-hop sequences, which feature an autocorrelation function with zero sidelobes and crosscorrelation function of at most 1. Consequently, the number of stations in the network and the number of simultaneous users that can be supported is greatly increased. The system is suitable for truly asynchronous highly secure LAN applications.
TL;DR: A new family of stochastic gradient adaptive filter algorithms is proposed which is based on mixed error norms which combine the advantages of different error norms, for example the conventional, relatively well-behaved, least mean square algorithm and the more sensitive, but better converging, least means fourth algorithm.
Abstract: A new family of stochastic gradient adaptive filter algorithms is proposed which is based on mixed error norms These algorithms combine the advantages of different error norms, for example the conventional, relatively well-behaved, least mean square algorithm and the more sensitive, but better converging, least mean fourth algorithm A mixing parameter is included which controls the proportions of the error norms and offers an extra degree of freedom within the adaptation A system identification simulation is used to demonstrate the performance of a least mean mixed-norm (square and fourth) algorithm
TL;DR: In this paper, the current/voltage characteristic collapse under a high drain bias in AlGaN/GaN heterostructure insulated gate field effect transistors (HIGFETs) grown on sapphire substrates is described.
Abstract: The authors describe the current/voltage characteristic collapse under a high drain bias in AlGaN/GaN heterostructure insulated gate field effect transistors (HIGFETs) grown on sapphire substrates. These devices exhibit a low resistance state and a high resistance state, before and after the application of a high drain voltage, respectively. At room temperature, the high resistance state persists for several seconds. The device can also be returned into the low resistance state by exposing it to optical radiation. Electron trapping in the gate insulator near the drain edge of the gate is a possible mechanism for this effect, which is similar to what has been observed in AlGaAs/GaAs HFETs at cryogenic temperatures.
TL;DR: In this article, direct point-to-point writing of buried single-mode channel waveguides using a focused, continuous wave, UV laser beam is demonstrated, showing that the waveguide has high sensitivity to UV induced index changes.
Abstract: Germanosilicate film waveguides fabricated by plasma enhanced chemical vapour deposition have been shown to possess high sensitivity towards UV induced index changes. As an illustration of possible future applications, direct point-to-point writing of buried singlemode channel waveguides using a focused, continuous wave, UV laser beam is demonstrated.
TL;DR: A new type of interleaver for rate 1/2 turbo codes is designed which allows each information bit to be associated with its own coded bit, which provides twice the performance over a block interleavers.
Abstract: A new type of interleaver for rate 1/2 turbo codes is designed which allows each information bit to be associated with its own coded bit. In this way the correction capability of the code is uniformly distributed over all information bits. This provides twice the performance over a block interleaver.
TL;DR: The concept of multistage secret sharing (MSS) is proposed and a general implementation of MSS schemes given.
Abstract: The concept of multistage secret sharing (MSS) is proposed and a general implementation of MSS schemes given. In such a scheme, many secrets are shared in such a way that all secrets can be reconstructed separately. Each share is of the same size as that of any single shared secret.
TL;DR: In this article, the authors proposed a new technique which will provide a solution in the case of numerical models, an important consideration as their importance within the field of systems engineering grows rapidly.
Abstract: The 'Q' parameter is currently the favoured metric for evaluating the performance of long span optically amplified systems. Q measurements have proved to be unreliable when excess patterning effects are present. A laboratory solution to this has already been provided. In the Letter, the authors detail a new technique which will provide a solution in the case of numerical models, an important consideration as their importance within the field of systems engineering grows rapidly.
TL;DR: Low profile rectangular dielectric resonator antennas, fabricated out of a very high permittivity material ( epsilon /sub r/=100), were reported in this paper. But their performance was limited to 3% bandwidth.
Abstract: Low profile rectangular dielectric resonator antennas, fabricated out of a very high permittivity material ( epsilon /sub r/=100) are reported. An antenna having a height of approximately 0.026 lambda /sub 0/ and a bandwidth of 3% is demonstrated.<
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TL;DR: In this paper, a GaN MESFET with a 0.25 mu m thick channel on a high resistivity GaN layer grown by metal organic vapour phase epitaxy was fabricated.
Abstract: GaN MESFETs have been fabricated with a 0.25 mu m thick channel on a high resistivity GaN layer grown by metal organic vapour phase epitaxy. These devices have a transconductance of 20 mS/mm. For a 0.7 mu m gate length device, the measured f/sub T/ and f/sub max/ were 8 and 17 GHz, respectively.
TL;DR: The authors present schemes in which the communication costs are low in comparison to the basic scheme and which can be constructed from the Nyberg-Rueppel digital signature scheme.
Abstract: A possible application of the Nyberg-Rueppel digital signature scheme is for authenticated encryption. The authors present schemes in which the communication costs are low in comparison to the basic scheme and which can be constructed from the Nyberg-Rueppel digital signature scheme.
TL;DR: In this article, a periodic poling of z-cut lithium niobate is reliably achieved in 0.2 mm thick samples, patterned with photoresist on one face and subjected to pulsed electric fields via liquid electrodes.
Abstract: Periodic poling of z-cut lithium niobate is reliably achieved in 0.2 mm thick samples, patterned with photoresist on one face and subjected to pulsed electric fields via liquid electrodes. The acceptance bandwidth for third order second-harmonic generation reveals that the full 3.3 mm length contributes to the conversion.
TL;DR: In this paper, the authors derived expressions for the sheet resistance of a Salisbury screen radar absorber which will yield the maximum bandwidth for a specified level of reflectivity performance, angle of incidence and polarisation.
Abstract: The author derives expressions for the sheet resistance of a Salisbury screen radar absorber which will yield the maximum bandwidth for a specified level of reflectivity performance, angle of incidence and polarisation. Design curves are also given which relate the maximum absorber bandwidth, reflectivity performance and spacer dielectric constant.
TL;DR: In this paper, a wide bandwidth high reflectivity distributed Bragg reflector (DBR) using the native oxide of AlAs as the low refractive index layer and GaAs as high this paper was designed and fabricated.
Abstract: The authors have designed and fabricated a wide bandwidth high reflectivity distributed Bragg reflector (DBR) using the native oxide of AlAs as the low refractive index layer and GaAs as the high refractive index layer. Results show that the refractive index of the native oxide is 1.55+or-0.01, the peak reflectivity of the DBR is over 99%, and the reflectivity bandwidth is approximately 460 nm. >
TL;DR: In this article, the first all-optical demultiplexing of TDM data at 250Gbit/s was presented. Butts et al. proposed a TDM-based TDM demULTiplexer, called a "TOAD", which is compact and requires sub-picojoule switching energy.
Abstract: The first demonstration of all-optical demultiplexing of TDM data at 250Gbit/s is reported. The demultiplexer, called a 'TOAD', is compact and requires sub-picojoule switching energy. Crosstalk measurements of pseudorandom data in adjacent, 4ps-width time slots, exhibit a BER of less than 10-9, with strong jitter immunity.
TL;DR: In this article, the sensitivity of the narrow bandpass peak to alignment and position of the phase shift in phase masks has been investigated in photosensitive optical fibres using phase shifted phase masks.
Abstract: 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.
TL;DR: In this paper, a novel method for writing fibre Bragg gratings is introduced, which consists of translating a UV beam along the fibre through a phase mask, and the phase mask and the fibre are held together, the phase of the interference pattern generated by the mask is not altered when the beam is translated along the mask.
Abstract: A novel method for writing fibre Bragg gratings is introduced. The method consists of translating a UV beam along the fibre through a phase mask. Because the phase mask and the fibre are held together, the phase of the interference pattern generated by the mask is not altered when the beam is translated along the mask. Gratings up to 1.5 cm long, limited by the mask dimensions, and with 98.5% reflection have been written in that way.
TL;DR: In this paper, the use of F. genetic algorithm removes the restrictions imposed on the array element displacements in order to obtain the linear analytic solution and the results presented show that it is possible to steer the array nulls precisely to the required interference directions and to achieve prescribed null depths.
Abstract: . t geneti- algorithm has been used for null steering in phased and :,daptive arrays. It has been shown that it is possible to steer the tray nul ls precisely to the required interference directions and to chieve ny prescribed null depths . A comparison with the results brained from the analytic anlution shows the advatages of using he genetic algorithm for null steering in linear array patterns. fntroduc ion: Nu :. steering in adaptive arrays can be achieved by element ,position perturbations [1 -3]. This technique is based on the assn ; sption. of. relatively smell element position perturbations so that r a analytic solution can be formulated . Results were given for displ tcemects of the elements both along , and normal to, the axis of Cu array . In this Letter , we report the use of a genetic algorithm (4) in the realisation of adaptive nulling by element position perturbations. The use of F. genetic algorithm removes the restrictions imposed on the array element displacements in order to obtain the linear analytic solution . The results presented show that it is possible to steer the array nulls precisely to the required interference dire Lions and to achieve prescribed null depths.
TL;DR: The Letter presents a calibration algorithm for arrays whose spatial responses are perturbed by mutual coupling and unknown sensor gains and phases that does not require the length of the true steering vector to be known explicitly.
Abstract: The Letter presents a calibration algorithm for arrays whose spatial responses are perturbed by mutual coupling and unknown sensor gains and phases. Unlike the algorithm proposed by Pierre and Kaveh (1991), the algorithm that the authors propose does not require the length of the true steering vector to be known explicitly. >