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Online ISSN 1350-911X Print ISSN 0013-5194

Electronics Letters

Volume 29, Issue 2, 21 January 1993

Volumes & issues:

Volume 29, Issue 2

21 January 1993

The semiconductor laser beyond the locking range of optical injection
  • Author(s): G.H.M. van Tartwijk ; G. Muijres ; D. Lenstra ; M.P. van Exter ; J.P. Woerdman
  • Source: Electronics Letters, Volume 29, Issue 2, p. 137 –138
  • DOI:  10.1049/el:19930092
  • Type: Article
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  • p. 137 –138 (2)
    The voltage of a current-driven optically injected semiconductor laser has been measured. The experiments not only show the well known phenomenon of injection locking but also reveal unprecedented dispersive-like structures around the relaxation oscillation frequencies. Based on the single-mode rate equations a theoretical explanation of both phenomena is given. The dispersive-like structures are shown to be caused by four wave mixing.
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Zero-bias modulation of tensile-strained InGaAs/InGaAsP quantum well lasers with wide phase margins
Erbium-doped phosphosilicate glass waveguide amplifier fabricated by PECVD
Clock recovery based on a new type of selfpulsation in a 1.5 μm two-section InGaAsP-InP DFB laser
Capacity per unit cost of a discrete memoryless channel
Reference phases of low peak factor multiharmonic signals
  • Author(s): J.O. Flower ; A.S. McCormack ; K.R. Godfrey
  • Source: Electronics Letters, Volume 29, Issue 2, p. 144 –145
  • DOI:  10.1049/el:19930097
  • Type: Article
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  • p. 144 –145 (2)
    Use is made of the reference phase of low peak factor multiharmonic signals in identification experiments. It is shown that the reference phase can be used to suppress the transient of a large time constant during excitation, allowing significant reductions in experimental time. It is also shown that reference phasing can eliminate the output drift inherent when testing type 2 systems.
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High-power 1.02 μm InGaAs/AlGaAs strained quantum well lasers with GaInP buried waveguides for pumping Pr3+-doped optical fibre amplifier
  • Author(s): K. Fukagai ; H. Chida ; S. Ishikawa ; H. Fujii ; K. Endo
  • Source: Electronics Letters, Volume 29, Issue 2, p. 146 –147
  • DOI:  10.1049/el:19930098
  • Type: Article
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  • p. 146 –147 (2)
    High power 1.02 μm single spatial mode laser diodes with low-loss (3.3 cm−1) GaInP buried waveguides have been developed for pumping Pr3+-doped optical fibre amplifiers. A maximum CW light output power of 415 mW and an optical fibre output of 71 mW at 200 mA have been achieved. A preliminary lifetest showed stable operation for over 2300 h under 100 mW CW conditions at 50°C.
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Noise performance of a GaAs MESFET as an optical detector and as an optoelectronic mixer in analogue optical links
  • Author(s): Z. Ürey ; D. Wu ; N.J. Gomes ; P.A. Davies
  • Source: Electronics Letters, Volume 29, Issue 2, p. 147 –149
  • DOI:  10.1049/el:19930099
  • Type: Article
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  • p. 147 –149 (3)
    Noise measurements with a GaAs MESFET employed as a photodetector or as an optoelectronic mixer are reported. Despite its higher noise it is shown that with proper biasing the GaAs MESFET provided a higher carrier-to-noise ratio than a pin photodiode, and as an optoelectronic mixer provided a comparable signal-to-noise ratio to that of a conventional pin and microwave mixer combination. The implications of using GaAs MESFETs in these configurations are discussed.
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All laser diode compression of 5 GHz picosecond pulses using cross-phase modulation in optical fibre
  • Author(s): A.D. Ellis  and  D.M. Patrick
  • Source: Electronics Letters, Volume 29, Issue 2, p. 149 –150
  • DOI:  10.1049/el:19930100
  • Type: Article
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  • p. 149 –150 (2)
    5 GHz pulses from a mode-locked semiconductor laser diode have been compressed from 10.5 to 4.6 ps by means of crossphase modulation using a separate optically amplified mode-locked laser diode. By tuning the laser wavelengths symmetrically about the 1.55 μm dispersion zero of an 11km length of fibre, the effect of group velocity dispersion is minimised, ensuring that the fibre is used efficiently. The spectral broadening induced by the cross-phase modulation enables pulse compression in a dispersive fibre.
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Plane wave propagation in uniaxial bianisotropic medium
  • Author(s): I.V. Lindell  and  A.J. Viitanen
  • Source: Electronics Letters, Volume 29, Issue 2, p. 150 –152
  • DOI:  10.1049/el:19930101
  • Type: Article
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  • p. 150 –152 (3)
    The uniaxial bianisotropic medium is a generalisation of the bi-isotropic and chiral media which recently have been the subject to intensive research. Such a medium results, for example, when microscopic helices with parallel axes are positioned in a host dielectric in random locations. Plane wave propagation in such a medium is studied and a simple solution for the dispersion equation is found. Numerical examples for the wave number surfaces of the medium are given.
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Effects of PRMA on objective speech quality
  • Author(s): J.C.S. Cheung ; L. Hanzo ; W.T. Webb ; R. Steele
  • Source: Electronics Letters, Volume 29, Issue 2, p. 152 –153
  • DOI:  10.1049/el:19930102
  • Type: Article
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  • p. 152 –153 (2)
    When transmitting 32 kbit/s adaptive differential pulse (ADPCM) speech using Reed–Solomon error correction coding and 16 level quadrature amplitude modulation (16-QAM), our 20 slot packet reservation multiple access (PRMA) assisted cordless telecommunications (CT) scheme supported 36–38 speech users with negligible objective and subjective speech degradation. The average number of users per slot was nearly doubled due to deploying PRMA and toll quality speech was transmitted in a user bandwidth ∼ 11.6 kHz. For a channel signal-to-noise ratio (SNR) in excess of 25 dB, a Rayleigh fading channel and mobile speeds above 2 mph the speech segmental SNR degradation was less than 0.3 dB.
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Linearisation of high-ratio, wide-range bipolar current mirrors
Wideband gain flattened erbium fibre amplifier using a photosensitive fibre blazed grating
CELP based mixed-source model for very low bit rate speech coding
Lithium niobate electro-optic tunable filter with high sidelobe suppression
  • Author(s): I.R. Croston ; A.D. Carr ; N.J. Parsons ; S.N. Radcliffe ; L.J. St. Ville
  • Source: Electronics Letters, Volume 29, Issue 2, p. 157 –159
  • DOI:  10.1049/el:19930106
  • Type: Article
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  • p. 157 –159 (3)
    The first demonstration of a high sidelobe suppression, tunable, electro-optic filter fabricated in lithium niobate for 1.55 μm is reported. Weighting of the mode convenor structure using a Taylor distribution resulted in a −3 dB passband width of 1.6 nm and nearest sidelobes of −25 dB. A continuous, linear electro-optic tuning rate of ±30 V/nm is also reported.
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Switched-capacitor circuits using delay-line elements
  • Author(s): N. Tan  and  S. Eriksson
  • Source: Electronics Letters, Volume 29, Issue 2, p. 159 –160
  • DOI:  10.1049/el:19930107
  • Type: Article
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  • p. 159 –160 (2)
    A possible realisation of switched-capacitor integrators using delay-line elements is presented. Although parasitic sensitive, the proposed switched-capacitor integrator allows higher-frequency operation, dissipates less DC power and occupies less chip area than its counterpart using an operational amplifier. The realisation and simulation result of a second-order delta-sigma modulator employing the proposed integrators are also included.
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230 fs, 25 W pulses from conventional mode-locked laser diodes with saturable absorber created by ion implantation
Application of mismatched filter theory to bandpass impulse response measurements
  • Author(s): A. Molina  and  P.C. Fannin
  • Source: Electronics Letters, Volume 29, Issue 2, p. 162 –163
  • DOI:  10.1049/el:19930109
  • Type: Article
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  • p. 162 –163 (2)
    The Letter shows how a mismatched filter for the compression of a bandpass arbitrary length pseudorandom bit sequence (PRBS) may be generated. A comparison is made between the standard matched filter and the mismatched filter in terms of accuracy, dynamic range, noise gain, simplicity of implementation and flexibility to shape the probing pulse, when such filters are used for the determination of wideband bandpass impulse response measurements. This study was carried out in the context of mobile radio channel sounding.
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Fabrication of GaAs quantum wire structure using metal organic molecular beam epitaxy
  • Author(s): Y. Nomura ; Y. Morishita ; S. Goto ; Y. Katayama
  • Source: Electronics Letters, Volume 29, Issue 2, p. 163 –165
  • DOI:  10.1049/el:19930110
  • Type: Article
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  • p. 163 –165 (3)
    GaAs quantum wires (100 × 20 nm2) buried in AlAs layers have been successfully fabricated using metal organic molecular beam epitaxy (MOMBE) for the first time. The underlying growth mechanism is that, under appropriate As4 pressure in MOMBE, GaAs preferentially grows only on the sidewalls of the patterned (1̅1̅1̅)B substrate without any formation of GaAs on the (1̅1̅1̅)B surface.
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Systolic realisation for 1-D circular convolution using the Chinese remainder theorem
Banded matrix iterative approach to Monte-Carlo simulations of scattering of waves by large-scale random rough surface problems: TM case
Vertical microcavity optical amplifying switch
Microwave performance of 0.4 μm gate metamorphic In0.29Al0.71As/In0.3Ga0.7As HEMT on GaAs substrate
  • Author(s): P. Win ; Y. Druelle ; P. Legry ; S. Lepilliet ; A. Cappy ; Y. Cordier ; J. Favre
  • Source: Electronics Letters, Volume 29, Issue 2, p. 169 –170
  • DOI:  10.1049/el:19930114
  • Type: Article
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  • p. 169 –170 (2)
    MBE grown metamorphic In0.29Al0.71As/In0.3Ga0.7As/GaAs high electron mobility transistors have been successfully fabricated. A 0.4 μm triangular gate device showed transconductance as high as 700 mS/mm at a current density of 230 mA/mm. The measured fT was 45 GHz and fmax was 115 GHz. These high values are, to the author's knowledge, the first reported for submicrometre metamorphic InAlAs/InGaAs/GaAs HEMTs with an indium content of 30%.
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High wallplug efficiency vertical-cavity surface-emitting lasers using lower barrier DBR mirrors
Upconversion luminescence of Er-doped ZnF2 channel waveguides grown by MBE
  • Author(s): M. Lui ; R.A. McFarlane ; D. Yap ; D. Lederman
  • Source: Electronics Letters, Volume 29, Issue 2, p. 172 –173
  • DOI:  10.1049/el:19930116
  • Type: Article
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  • p. 172 –173 (2)
    Planar waveguides of erbium doped ZnF2 on MgF2 substrates have been grown using molecular beam epitaxy and channel waveguides have been formed by ion milling. By exciting individual channels with an 800 nm pump, strong upconversion fluorescence has been generated at 410, 550 and 670 nm and at numerous weaker peaks. The fabrication technique can be adapted to semiconductor substrates for making compact diode-pumped visible and infra-red lasers.
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Experimental study of real time corona discharge imaging system
Short pulse, high power Q-switched Nd:MgO:LiNbO3 waveguide laser
  • Author(s): E. Lallier ; D. Papillon ; J.P. Pocholle ; M. Papuchon ; M. de Micheli ; D.B. Ostrowsky
  • Source: Electronics Letters, Volume 29, Issue 2, p. 175 –176
  • DOI:  10.1049/el:19930118
  • Type: Article
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  • p. 175 –176 (2)
    An efficient monolithic Q-switched Nd:MgO:LiNbO3 waveguide laser operating at 1.085 μm is reported. Q-switched pulses of 350 W peak power and 300 ps width are obtained for less than 15 mW of CW 0.814 μm coupled pump power. This source was frequency-doubled in an external quasiphase-matched LiNbO3 waveguide yielding 12 W pulses at 0.54 μm with a 15% conversion efficiency.
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Suppression of nonstationary sinusoidal interference using transform domain median filtering
  • Author(s): T. Kasparis
  • Source: Electronics Letters, Volume 29, Issue 2, p. 176 –178
  • DOI:  10.1049/el:19930119
  • Type: Article
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  • p. 176 –178 (3)
    A novel technique for the suppression of sinusoidal interference by using transform domain median filtering is proposed. The most important advantage of this new technique is that estimation of the interference frequency is not needed. Other important advantages are also discussed. Residual errors are examined and compared with that of notch filtering. Experimental results with random binary sequences are presented.
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Lattice quantisation for image sequences coding at 16 dimension
  • Author(s): D.G. Sampson  and  M. Ghanbari
  • Source: Electronics Letters, Volume 29, Issue 2, p. 178 –179
  • DOI:  10.1049/el:19930120
  • Type: Article
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  • p. 178 –179 (2)
    The performance of a 16-dimensional lattice quantisation scheme is investigated. A simple Ek-type lattice which includes all the necessary shape patterns for reliable image reconstruction in a codebook of manageable size, is devised to replace the most dense Λ16. Simulation results demonstrate that E16-based LQ achieves better signal-to-noise ratio performance than Λ16, still at only 1 : 16 of Λ16 encoding complexity.
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New compensation method for tuned optical receivers with feedback
  • Author(s): E. Drijver
  • Source: Electronics Letters, Volume 29, Issue 2, p. 179 –181
  • DOI:  10.1049/el:19930121
  • Type: Article
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  • p. 179 –181 (3)
    A new compensation method for serial tuned optical receivers with overall current shunt feedback is described. At the cost of only one extra tuning inductor, a stable receiver has been obtained with a flat frequency response and improved noise performance, without the necessity of an equalisation circuit. A low-cost heterodyne receiver (300–900 MHz) has been realised with 4 dB noise reduction, using standard packaged components.
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Prewindowed and postwindowed methods for bispectrum estimation via AR modelling
  • Author(s): A. Gallego ; M.C. Carrión ; D.P. Ruiz ; A. Medouri
  • Source: Electronics Letters, Volume 29, Issue 2, p. 181 –182
  • DOI:  10.1049/el:19930122
  • Type: Article
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  • p. 181 –182 (2)
    Two new autoregressive parametric methods for the bispectrum estimation of a stationary process are presented. These are an extension of the prewindowed (PREW) and postwindowed (POSW) methods for the estimation of a power spectrum via AR modelling. A variant of each of these methods, based on the segmentation of process data into coupled records, is also presented. Simulations show that the POSW and PREW methods produce similar results to those obtained using the third order recursion (TOR) and constrained third-order mean (CTOM) methods, respectively, and that their modifications provide a more precise estimation than that obtained using the TOR and CTOM methods of the AR-model parameters.
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Loaded-wire node for TLM method
Multiplierless structure for maximally flat linear phase FIR filters
Very fast CMOS glitch detector
New, simple method for simulating optical front end receivers
Recursive short-time Hartley transform
  • Author(s): H.-C. Chiang  and  J.-C. Liu
  • Source: Electronics Letters, Volume 29, Issue 2, p. 188 –190
  • DOI:  10.1049/el:19930127
  • Type: Article
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  • p. 188 –190 (3)
    The short-time Hartley transform (STHT) is a powerful tool for the spectral analysis of time-varying signals, where a portion of the signal is extracted by windowing, and the Hartley transform of the windowed signal is then taken. Moving the window by appropriate steps, the entire signal may be covered. The recursive short-time Hartley transform (RSTHT) developed in the Letter updates the new transform contents between two successive windowed frames, using less computation than that required in directly evaluating the new transform. For some cases such as the Hamming, Hanning, and Blackman windows, the recursive formulas are also derived for demonstration.
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Smooth vertical etching of AlGaInP by Cl2 reactive ion beam etching
  • Author(s): T. Yoshikawa ; Y. Sugimoto ; H. Yoshii ; H. Kawano ; S. Kohmoto ; K. Asakawa
  • Source: Electronics Letters, Volume 29, Issue 2, p. 190 –192
  • DOI:  10.1049/el:19930128
  • Type: Article
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  • p. 190 –192 (3)
    Very smooth vertical etching of AlGaInP is achieved for the first time by Cl2 reactive ion beam etching. The etched depth is precisely controlled (σ = 22 nm) by simply monitoring the electrode current of the ion accelerating grid, and the etched surface exhibits no contamination except for Cl, as observed by in situ Auger electron spectroscopy. Furthermore, other III-V compound semiconductors, such as AlGaInP/GaInP double heterostructures and InAlAs/InGaAs/InP multilayers, are also etched smoothly and vertically with no steps between the layers on the sidewalls.
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Algebraic design of some lower-order elliptic filters
Demonstration of a high speed optical drop function using a tunable DFB laser
Design of new time-varying sliding surface for robot manipulator using variable structure controller
  • Author(s): J.-J. Kim ; J.-J. Lee ; K.-B. Park ; M.-J. Youn
  • Source: Electronics Letters, Volume 29, Issue 2, p. 195 –196
  • DOI:  10.1049/el:19930131
  • Type: Article
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  • p. 195 –196 (2)
    A variable structure controller with time-varying sliding surface is proposed for robot manipulators. The proposed time-varing sliding surface ensures the existence of a sliding mode from an initial state, whereas the conventional sliding surface cannot achieve robust performance against parameter variations and disturbances before the sliding mode occurs. Therefore, error transients can be prescribed in advance for all time. Furthermore, it is shown that the overall system is globally exponentially stable. The efficiency of the proposed method for the trajectory tracking is demonstrated by an example.
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Adaptive hybrid ARQ scheme using multidimensional parity-check codes
Interpolation using the discrete cosine transform: reconsideration
High-power vertical-cavity surface-emitting lasers
Polarisation independent 8×8 waveguide grating multiplexer on InP
Sorcon switch: a new cell switching architecture
Two dimensional interpolation of real sequences using the DCT
  • Author(s): J.I. Agbinya
  • Source: Electronics Letters, Volume 29, Issue 2, p. 204 –205
  • DOI:  10.1049/el:19930137
  • Type: Article
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  • p. 204 –205 (2)
    The conventional discrete cosine transform (DCT) is used to perform two-dimensional (2-D) interpolation of real sequences. It is shown that with a suitble modification of the DCT multiplying coefficients, alias-free image interpolation is achieved. The algorithm is suitable for video signal decimation and interpolation. The normalised mean square error decreases as the size of the interpolated sequence increases. Accurate image interpolation without aliasing, blocking or snowing is achieved. Extension of the algorithm to three and higher dimensions is given.
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1 W (pulsed) vertical cavity surface emitting laser
Assessment of the polarisation loss dependence of transoceanic systems using a recirculating loop
Observation of BER degradation due to fading in long-distance optical amplifier system
Fabrication and characteristics of improved strained quantum-well GaInAlAs gain-coupled DFB lasers
  • Author(s): B. Borchert ; B. Stegmüller ; R. Gessner
  • Source: Electronics Letters, Volume 29, Issue 2, p. 210 –211
  • DOI:  10.1049/el:19930141
  • Type: Article
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  • p. 210 –211 (2)
    Results of improved 1.58 μm GaInAlAs strained quantum-well gain-coupled DFB lasers are presented. Besides the excellent spectral properties (singlemode yield of 75% and a sidemode suppression ratio of 45 dB), 20 mW output power and CW operation at 80%C have been obtained. A record 3 dB bandwidth of 11 GHz was measured. Spectral or dynamical instabilities due to the loss grating have not been observed.
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Improved negative dynamic resistance model for high voltage MOSFETs
Long wavelength broadband normal incidence AlAs/AlGaAs X-valley quantum well infra-red phototector
  • Author(s): Y. Zhang ; N. Baruch ; W.I. Wang
  • Source: Electronics Letters, Volume 29, Issue 2, p. 213 –214
  • DOI:  10.1049/el:19930143
  • Type: Article
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  • p. 213 –214 (2)
    The Letter demonstrates a long-wavelength broadband normal incidence infra-red photodetector based on bound state to extended state interconduction sub-band transitions in AlAs/AlGaAs X-valley quantum wells. High infra-red absorption coefficient and quantum efficiency (α = 1900 cm−1, η = 19%), wideband long wavelength photo-responsivity (λ = 7.8–17.1 μm) and low dark current (ID = 10−6 A at 68 K and Vb = 1 V) are achieved.
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Comment: Control of polarisation degradation in fibre amplifier WDMs
Reply: Control of polarisation degradation in fibre amplifier WDMs
Submicrometre silicon permeable base transistors with buried CoSi2 gates
  • Author(s): A. Schüppen ; L. Vescan ; M. Marso ; A.V.D. Hart ; H. Lüth ; H. Beneking
  • Source: Electronics Letters, Volume 29, Issue 2, p. 215 –217
  • DOI:  10.1049/el:19930146
  • Type: Article
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  • p. 215 –217 (3)
    Silicon permeable base transistors (PBTs) with monocrystalline buried CoSi2 gates have been fabricated by local high dose cobalt ion implantation through a grid-like mask into epitaxial Si (100) layers and homoepitaxial Si over-growth by low-pressure vapour phase epitaxy. The PBTs show good DC characteristics and pinchoff at zero or at low negative gate voltages, respectively. Transistors with a grating periodicity of 0.6 μm reach a maximum trans-conductance gm of 70 mS/mm. The highest obtained transit frequency is fT = 6 GHz.
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Structure for time-varying paraunitary filter banks with perfect reconstruction
Comment: Performance of crossbar interconnection networks in the presence of ‘hot spots’
Reply: Performance of crossbar interconnection networks in the presence of hot spots
4.5 W CW, near-diffraction-limited tapered-stripe semiconductor optical amplifier
Tuning characteristics of Gunn diode in conical-section waveguide mounts
Fast approximate moment method model for monopole arbitrarily positioned on circular ground plane
New methods for accurate modelling of wires using TLM
  • Author(s): A.P. Duffy ; T.M. Benson ; C. Christopoulos ; J.L. Herring
  • Source: Electronics Letters, Volume 29, Issue 2, p. 224 –226
  • DOI:  10.1049/el:19930153
  • Type: Article
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  • p. 224 –226 (3)
    The simulation of wires is essential for the numerical modelling of many problems, such as those related to electromagnetic compatibility (EMC). The Letter identifies the cause of errors occurring when modelling wires using the transmission-line modelling (TLM) method. A new approach is proposed which is shown to give good agreement between simulated and experimental results.
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Comment: Physical interpretation of reduction of soliton interaction forces by bandwidth limited amplification
Reply: Physical interpretation of reduction soliton interaction forces by bandwidth limited amplification
Demultiplexing using crossphase modulation-induced spectral shifts and Kerr polarisation rotation in optical fibre
Trellis coded multi-h CPM for power and bandwidth efficiency
  • Author(s): T. Ertaş  and  F.S.F. Poon
  • Source: Electronics Letters, Volume 29, Issue 2, p. 229 –230
  • DOI:  10.1049/el:19930157
  • Type: Article
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  • p. 229 –230 (2)
    It is well known that the rate (n − 1)/n convolutional codes combined with 2n-level CPM have good power-bandwidth performance with encoder independent upper bounds. In the Letter, a scheme combining rate 2/3 convolutional codes with 8-level multi h CPM is shown to have better power-bandwidth performance over the upper bound than the scheme with single h. Results obtained over a wide range of h combinations are also presented.
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Improved signal-to-noise ratio in gain-levered InGaAs/InP MQW lasers
64 to 8 Gbit/s all-optical demultiplexing experiment with clock recovery using new phase lock loop technique
Reliable, high-power, singlemode, 630–640 nm Ga0.5In0.5P/GaAlInP ridge waveguide laser diodes
  • Author(s): S.S. Ou ; M. Jansen ; J.J. Yang ; R.J. Fu ; C.J. Hwang
  • Source: Electronics Letters, Volume 29, Issue 2, p. 233 –234
  • DOI:  10.1049/el:19930160
  • Type: Article
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  • p. 233 –234 (2)
    Single-longitudinal and stable fundamental-mode operation to CW output powers of 40 mW, and maximum CW output powers of 46 mW at a wavelength of 636 nm were achieved for 10 μm-wide, 1200 μm-long GaInP/GaAlInP ridge waveguide laser diodes at room temperature. Ongoing lifetests indicate stable 5 and 20 mW operation of more than 2000 and 1200 h at room temperature with extrapolated lifetimes > 10000 and 6000 h, respectively.
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Low noise near infra-red detection system using InGaAs pin photodiode
  • Author(s): I. Mizumoto  and  S. Mashiko
  • Source: Electronics Letters, Volume 29, Issue 2, p. 234 –236
  • DOI:  10.1049/el:19930161
  • Type: Article
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  • p. 234 –236 (3)
    A low noise detection system using an pin photodiode for near infra-red spectroscopic measurement was developed. The InGaAs pin photodiode is more suitable than the Ge pin photodiode for detecting low level light as regards dark current and quantum efficiency. The detection system consists of an InGaAs pin photodiode with a charge integrating amplifier (InGaAs-CIA) operated at 77 K. The minimum detectable power of 10−16 W was achieved at 1.28 μm wavelength.
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Current-mode fuzzy memory element
Low phonon-energy glasses for efficient 1.3 μm optical fibre amplifiers
  • Author(s): D.W. Hewak ; R.S. Deol ; J. Wang ; G. Wylangowski ; J.A. Mederios Neto ; B.N. Samson ; R.I. Laming ; W.S. Brocklesby ; D.N. Payne ; A. Jha ; M. Poulain ; S. Otero ; S. Surinach ; M.D. Baro
  • Source: Electronics Letters, Volume 29, Issue 2, p. 237 –239
  • DOI:  10.1049/el:19930163
  • Type: Article
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  • p. 237 –239 (3)
    The results of an experimental and theoretical study to compare the attributes of Pr3+-doped sulphide, chloride, mixed halide, fluoride and chlorotellurite glasses for 1.3 μm fibre amplifiers are presented. Quantum efficiencies based on measured and calculated radiative and nonradiative rates are presented for each glass together with its 1.3 μm fluorescence spectrum and an estimate of its loss.
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Wafer-scale uniformity of vertical-cavity lasers grown by modified phase-locked epitaxy technique
High power InGaAs-GaAs-InGaP buried heterostructure strained quantum well lasers grown by two step MOVPE
  • Author(s): Y.K. Sin ; H. Horikawa ; T. Kamijoh
  • Source: Electronics Letters, Volume 29, Issue 2, p. 240 –242
  • DOI:  10.1049/el:19930165
  • Type: Article
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  • p. 240 –242 (3)
    Data are presented on device results from buried heterostructure InGaAs-GaAs strained quantum well lasers with In0.49Ga0.51P cladding layers (λL = 980 nm). AR-HR coated buried heterostructure lasers with a p-n InGaP current blocking junction show low laser thresholds of 3.1 mA and high output powers of 95 mW both measured CW at RT, and this is the first demonstration of InGaAs-GaAs-InGaP buried heterostructure lasers entirely grown by a two step MOVPE process.
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Influence of rapid thermal nitridation process in N2O ambient on the endurance performance of FLOTOX EEPROM cells
  • Author(s): C. Papadas ; P. Mortini ; G. Ghibaudo ; G. Pananakakis ; F. Pio ; C. Riva
  • Source: Electronics Letters, Volume 29, Issue 2, p. 242 –243
  • DOI:  10.1049/el:19930166
  • Type: Article
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  • p. 242 –243 (2)
    A comparison between the endurance characteristics obtained on FLOTOX EEPROM cells with pure SiO2 as the tunnel insulator and rapid thermal processed nitrided oxides in N2O ambient is presented. The superiority of nitrided oxides for applications in future floating gate devices is demonstrated and the obtained higher reliability performance is attributed quantitatively to nitrogen incorporation in the tunnel insulator layer.
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Channel capacity of (O, G/I) codes
  • Author(s): M.Č. Stefanović  and  B.V. Vasić
  • Source: Electronics Letters, Volume 29, Issue 2, p. 243 –245
  • DOI:  10.1049/el:19930167
  • Type: Article
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  • p. 243 –245 (3)
    The tables of channel capacities of the (O, G/I) constrained systems are presented. It is shown that for the given timing parameter G there exists a critical path memory length of the Viterbi algorithm, Iδ, over which it is not possible to improve the code efficiency if data and codeword lengths are limited. These maximal code efficiencies for practically interesting values of G are listed.
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Dimensioning of leaky buckets to be used as monitors
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