Online ISSN
1350-911X
Print ISSN
0013-5194
Electronics Letters
Volume 24, Issue 18, 1 September 1988
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Volume 24, Issue 18
1 September 1988
High-power, high-efficiency 770 nm 2D laser diode array
- Author(s): A. Rosenberg ; J.C. McShea ; A.R. Bogdan ; J.C. Petheram ; A. Rosen ; D. Bechtle ; P.S. Zory ; J.W. Sprague ; J.R. Shealy
- Source: Electronics Letters, Volume 24, Issue 18, p. 1121 –1122
- DOI: 10.1049/el:19880762
- Type: Article
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A two dimensional (2D) laser diode array is described which operates at a power density of 2 kW/cm2, with an overall efficiency of 35% and a slope efficiency of 56%. The wavelength of operation is 770 nm.
Polarisation-independent LiNbO3, 4×4 matrix switch
- Author(s): H. Nishimoto ; S. Suzuki ; M. Kondo
- Source: Electronics Letters, Volume 24, Issue 18, p. 1122 –1123
- DOI: 10.1049/el:19880763
- Type: Article
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The first polarisation-independent LiNbO3 strictly nonblocking 4 × 4 matrix switch has been developed. This matrix switch has a 4–6 dB insertion loss at any incident polarisation with 1.3μm wavelength and about 30 V switching voltage.
Low threshold current GaAs/AlGaAs GRIN-SCH lasers grown by molecular beam epitaxy on Si3N4 masked substrates
- Author(s): H.P. Meier ; E. van Gieson ; W. Walter ; C. Harder ; P. Buchmann ; D. Webb ; A. Moser
- Source: Electronics Letters, Volume 24, Issue 18, p. 1123 –1125
- DOI: 10.1049/el:19880764
- Type: Article
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High-performance single-quantum-well graded-refractive-index separate confinement heterostructure (SQW GRIN-SCH) lasers have been grown by molecular beam epitaxy on Si3N4 patterned GaAs (100) substrates. Lasers grown on stripe windows orientated in the [011] direction have optical waveguiding and current confinement supplied by facetting occurring during growth. Lasers fabricated on 10μm wide Si3N4 openings have threshold currents as low as 15 mA for a 500 μm-long cavity. The current density required to reach optical transparency is 144 A/cm2, an internal quantum efficiency of 81%, and a peak optical power of 70 mW per facet has been obtained. Device performance comparable to ridge lasers is observed in a self-aligned laser process.
Explanation and modelling of pulse compression and broadening in near-travelling-wave laser amplifiers
- Author(s): A.J. Lowery
- Source: Electronics Letters, Volume 24, Issue 18, p. 1125 –1126
- DOI: 10.1049/el:19880765
- Type: Article
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Simulations using a transmission-line laser model show that optical pulse compression and broadening, recently observed in near-travelling-wave laser amplifiers, results from gain saturation only. The amount of compression was found to be dependent on the input pulse shape and power but independent of its spectrum.
Evaluation of power penalty due to beat noise induced by connector reflection
- Author(s): M. Shikada and N. Henmi
- Source: Electronics Letters, Volume 24, Issue 18, p. 1126 –1128
- DOI: 10.1049/el:19880766
- Type: Article
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Power penalties caused by beat noise in a received optical signal beam were evaluated experimentally and theoretically. It was found that power penalties could be suppressed when the beam relative intensity noise was reduced to less than −135 dB/Hz below 2.4 Gbit/s. This goal can be satisfied using a commercially available physical contact optical connector, which has less than −20 dB reflection.
CMOS delay time model based on weighted peak current
- Author(s): K.H. Kim and S.B. Park
- Source: Electronics Letters, Volume 24, Issue 18, p. 1128 –1129
- DOI: 10.1049/el:19880767
- Type: Article
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We propose a new CMOS delay time model with the configuration ratio, the input slope and the load condition taken into account. This model is based on the optimally weighted switching peak current. The delay equations are computationally effective and the error is typically within 10% of SPICE results.
Dynamic performance of current-sensing power MOSFETs
- Author(s): D. Grant and R. Pearce
- Source: Electronics Letters, Volume 24, Issue 18, p. 1129 –1131
- DOI: 10.1049/el:19880768
- Type: Article
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Errors in the output of current-sensing MOSFETs during switching are either perceived, due to measurement difficulties, or real, due to a change in sense ratio as the device passes from the linear to the fully enhanced region. Transformer action within the device package also produces transients and limits bandwidth.
Measurement of intrinsic frequency response of semiconductor lasers using optical modulation
- Author(s): C.H. Lange ; J. Eom ; C.B. Su ; J. Schlafer ; R.B. Lauer
- Source: Electronics Letters, Volume 24, Issue 18, p. 1131 –1132
- DOI: 10.1049/el:19880769
- Type: Article
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For the first time, optical modulation is used to determine the intrinsic frequency response of a laser diode. It is shown that the shape of the measured frequency response agrees very well with the predicted intrinsic response of semiconductor lasers. As anticipated, the measured frequency response lacks the frequency rolloff that occurs with direct RF current modulation. The resonant frequencies measured are shown to be proportional to the square root of the probe laser bias power and the damping rates are found to be linear in power, in agreement with expectations.
Wide bandwidth low noise pinFET receiver for high-bit-rate optical preamplifier applications
- Author(s): L.D. Tzeng and R.E. Frahm
- Source: Electronics Letters, Volume 24, Issue 18, p. 1132 –1134
- DOI: 10.1049/el:19880770
- Type: Article
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A wide bandwidth low noise pinFET receiver has been fabricated and characterised for optical preamplifier applications. The receiver uses a low capacitance planar pin diode as the photodetector. A bandwidth of 7.08 GHz was measured. The measured input noise current for the receiver front-end is lower than 12 pA/√(f). Using a 1.3 μm DFB laser as the transmitter, at a data rate of 4 Gbit/s, the measured receiver sensitivity is −25.5 dBm with a bit-error-rate of 1 × 10−9. A set of two of such receivers has also been tested in a 1.3 μm polarisation-insensitive optical preamplifier system experiment. The measured receiver sensitivity, including an optical insertion loss of 1.5 dB, is −29.3 dBm.
GaAs MIS structures with SiO2 using a thin silicon interlayer
- Author(s): G.G. Fountain ; S.V. Hattangady ; D.J. Vitkavage ; R.A. Rudder ; R.J. Markunas
- Source: Electronics Letters, Volume 24, Issue 18, p. 1134 –1135
- DOI: 10.1049/el:19880771
- Type: Article
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The introduction of a pseudomorphic Si interlayer, about 1.0 nm thick, is found to dramatically improve the MIS characteristics of the SiO2/GaAs system. Quasistatic and high-frequency capacitance/voltage (C/V) data from such a novel capacitor structure on n-GaAs indicate that the surface of the GaAs is swept from inversion to accumulation. X-ray photoelectron spectroscopy and ion scattering spectroscopy confirm the presence of the Si layer and its complete coverage of the GaAs surface. The Si layer minimises the formation of any detrimental native oxides and thus controls the chemical nature of the GaAs surface. This approach has implications in the development of metal-insulator-semiconductor systems in general.
Efficient operation of an Yb-sensitised Er fibre laser at 1.56 μm
- Author(s): M.E. Fermann ; D.C. Hanna ; D.P. Shepherd ; P.J. Suni ; J.E. Townsend
- Source: Electronics Letters, Volume 24, Issue 18, p. 1135 –1136
- DOI: 10.1049/el:19880772
- Type: Article
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We report operation of a high-efficiency Yb : Er single-mode fibre laser. Pumping at wavelengths of 1064 nm and at 820 nm has shown low pump power thresholds (<7 and 4 mW) and high slope efficiencies (4.2 and 7.0%).
Propagation modelling in the troposphere: parabolic equation method
- Author(s): K.H. Craig
- Source: Electronics Letters, Volume 24, Issue 18, p. 1136 –1139
- DOI: 10.1049/el:19880773
- Type: Article
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The parabolic equation is a simplification of the wave equation that admits an efficient full wave solution to the problem of microwave propagation in a two-dimensional refractive index structure. Field strength diagrams for propagation in the presence of typical elevated ducting layers are given. The fields are significantly more complicated than can be predicted by one-dimensional mode methods.
Simple stereo algorithm for 3D positioning of object points
- Author(s): J.S. Lee ; J. Lim ; Z. Bien
- Source: Electronics Letters, Volume 24, Issue 18, p. 1139 –1140
- DOI: 10.1049/el:19880774
- Type: Article
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A simple stereo algorithm for 3D positioning of object points is presented. The superimposed difference image is formed from a pair of stereo images. The features are extracted from only the superimposed difference image and the disparity is determined by searching paired features in the given window without recourse to the stereo matching.
Novel wavelength-resonant optoelectronic structure and its application to surface-emitting semiconductor lasers
- Author(s): M.Y.A. Raja ; S.R.J. Brueck ; M. Osiński ; C.F. Schaus ; J.G. McInerney ; T.M. Brennan ; B.E. Hammons
- Source: Electronics Letters, Volume 24, Issue 18, p. 1140 –1142
- DOI: 10.1049/el:19880775
- Type: Article
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An optimised design for optoelectronic devices which depends on the interaction between an electromagnetic standing wave and the carrier population is described. The structure consists of quantum well layers spaced at one half the wavelength of a selected optical transition in quantum wells. This spatial periodicity allows the amplifying or absorbing medium (quantum wells) to coincide with the peaks of the standing wave optical field in the Fabry-Pérot cavity. In such a periodic medium, the gain or absorption for the selected wavelength is enhanced by a factor of two compared to a uniform medium. This concept was applied to fabricate a surface-emitting semiconductor laser in the GaAs/AlGaAs system. Lasing was achieved with the shortest gain medium length (320 nm) ever reported.
Polarisation independent switch and polarisation splitter employing Δβand ΔK modulation
- Author(s): P. Granestrand ; L. Thylen ; B. Stoltz
- Source: Electronics Letters, Volume 24, Issue 18, p. 1142 –1143
- DOI: 10.1049/el:19880776
- Type: Article
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We report a novel type of polarisation independent directional coupler switch on X-cut, Y-propagating Ti: LiNbO3, with modest fabrication tolerances. The device can also be used as a polarisation splitter. The principle of operation and experimental results are given.
Monolithic GaInAs/InP photodetector arrays for high-density wavelength division multiplexing (HDWDM) applications
- Author(s): W.S. Lee ; S.W. Bland ; A.J. Robertson
- Source: Electronics Letters, Volume 24, Issue 18, p. 1143 –1145
- DOI: 10.1049/el:19880777
- Type: Article
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Monolithic arrays of interdigitated GaInAs/InP photodetectors have been fabricated for high density wavelength division multiplexing (HDWDM) applications. The detectors typically exhibit a reverse leakage current of 400 nA, capacitance of less than 70 fF and a responsivity of 0.5 A/W at −5 V bias. An optical crosstalk of −33.4 dB has been measured between adjacent detectors in an experimental grating demultiplexer system. Preliminary electrical crosstalk measurements in the frequency range of 1–500 MHz indicate signal isolation of the order of 46 dB.
Integrated directional couplers with photodetectors by hydride vapour phase epitaxy
- Author(s): S. Chandrasekhar ; J.C. Campbell ; F.G. Storz ; A.G. Dentai ; C.H. Joyner ; G.J. Qua ; T.J. Bridges
- Source: Electronics Letters, Volume 24, Issue 18, p. 1145 –1146
- DOI: 10.1049/el:19880778
- Type: Article
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The hydride vapour-phase-epitaxial crystal growth technique has been used to realise integrated waveguide-photodetectors and, for the first time, integrated directional coupler-photodetectors for detection in the 1.3μm to 1.55μ wavelength range. The GaInAsP waveguides which formed the directional couplers had propagation losses of 2 ± 0.5d B/cm and more than 90% of the guided light was coupled into the photodetectors. The directional couplers were symmetric with respect to the launch port and had 3dB coupling lengths of about 1.45 mm.
Novel mass-fabrication of fibre couplers using arrayed fibre ribbons
- Author(s): I. Yokohama ; K. Chida ; H. Hanafusa ; J. Noda
- Source: Electronics Letters, Volume 24, Issue 18, p. 1147 –1148
- DOI: 10.1049/el:19880779
- Type: Article
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To achieve high productivity and high density packaging of fibre couplers for practical systems, a novel mass-fabrication process using arrayed fibre ribbons has been developed. The fabricated arrayed-fibre coupler consists of four couplers which are all fabricated together from four-fibre ribbons. Each fibre coupler had 3 dB coupling ratio to within 49.3 ± 2.1%. It has been confirmed that plural fibre couplers with equal coupling ratio can be simultaneously fabricated by the mass-fabrication process.
Combining fast DPCM compression of pictures with tree encoding
- Author(s): J. de Lameillieure and I. Bruyland
- Source: Electronics Letters, Volume 24, Issue 18, p. 1148 –1150
- DOI: 10.1049/el:19880780
- Type: Article
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This contribution presents a fast DPCM coder built around a ROM of feasible size, in which an elementary form of tree encoding is integrated, to improve the quality of the decodedpicture. Simulations illustrate the improvements of this technique in comparison with normal DPCM encoding.
Computer analysis of finite planar arrays of circular multimode horns
- Author(s): E. Kühn ; H. Wolf ; H. Viskum
- Source: Electronics Letters, Volume 24, Issue 18, p. 1150 –1151
- DOI: 10.1049/el:19880781
- Type: Article
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Software for accurately modelling finite planar arrays of identical circular multimode horns with arbitrary wall contours has been developed and validated. The letter describes the analysis concept followed, and presents a comparisonbetween theoretical and experimental results.
Direct timing extraction in a modified-Manchester coded picosecond optical pulse fibre optic transmission system
- Author(s): H. Izadpanah
- Source: Electronics Letters, Volume 24, Issue 18, p. 1151 –1153
- DOI: 10.1049/el:19880782
- Type: Article
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Direct timing extraction in a modified-Manchester-coded fibre optic transmission system is demonstrated. The presence of the clock signal in the received data is used to injection lock an electronic oscillator thus generating a large timing signal. The technique is also suitable for optical injection locking for timing extraction.
1×2 optical switch for WDM transmission systems
- Author(s): Y. Fujii
- Source: Electronics Letters, Volume 24, Issue 18, p. 1153 –1154
- DOI: 10.1049/el:19880783
- Type: Article
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A 1×2 optical switch, which also functions as wavelength demultiplexer, is designed and experimentally fabricated utilising a phase plate and a twisted nematic liquid crystal. Measured insertion loss, crosstalk attenuation, and transit time are <1.5 dB, >17.6 dB, and <80 ms, respectively.
Electronic compensation of saturation-induced crosstalk in optical amplifiers
- Author(s): T.E. Darcie ; R.M. Jopson ; A.A.M. Saleh
- Source: Electronics Letters, Volume 24, Issue 18, p. 1154 –1156
- DOI: 10.1049/el:19880784
- Type: Article
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A simple feedforward circuit is shown to reduce saturation-induced crosstalk in wavelength-multiplexed on-off-keyed optical amplifier applications. In this two-channel demonstration, crosstalk is reduced by 20dB while the effective gain of the amplifier is increased by 3 dB.
Microstrip transmission line excitation of dielectric resonator antennas
- Author(s): R.A. Kranenburg and S.A. Long
- Source: Electronics Letters, Volume 24, Issue 18, p. 1156 –1157
- DOI: 10.1049/el:19880785
- Type: Article
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A systematic investigation of the excitation of a cylindrical dielectric resonator antenna was undertaken to illustrate the possibility of such a feed structure and to characterise the coupling behaviour and radiation patterns of the system.
Optical amplification in a multichannel FSK coherent system
- Author(s): B. Glance ; G. Eisenstein ; P.J. Fitzgerald ; K.J. Pollock ; G. Raybon
- Source: Electronics Letters, Volume 24, Issue 18, p. 1157 –1159
- DOI: 10.1049/el:19880786
- Type: Article
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We report the crosstalk degradation caused by an optical amplifier in a densely spaced four-channel heterodyne FSK system. A maximum receiver sensitivity of 250 photons/bit is obtained for an optimum input signal level. This result is 5dB poorer than the sensitivity obtained in the absence of an optical amplifier.
Performance of a frequency-locked 1.3μm DFB laser under 50Mbit/s FSK modulation
- Author(s): Y.C. Chung ; R.W. Tkach ; A.R. Chraplyvy ; C.B. Roxlo
- Source: Electronics Letters, Volume 24, Issue 18, p. 1159 –1160
- DOI: 10.1049/el:19880787
- Type: Article
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A GaInAsP DFB laser modulated with a 50 Mbit/s pseudorandom AMI FSK signal was locked to the 2p10−3d5 transition of argon at 1.2960μm using the optogalvanic effect. No significant degradation in frequency stability due to the modulation was observed. When the signal was demodulated, the power penalty due to the frequency-locking servo loop was found to be less than ⅓dB.
1.56 μm Yb-sensitised Er fibre laser pumped by diode-pumped Nd:YAG and Nd:YLF lasers
- Author(s): G.T. Maker and A.I. Ferguson
- Source: Electronics Letters, Volume 24, Issue 18, p. 1160 –1162
- DOI: 10.1049/el:19880788
- Type: Article
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We describe the performance of a highly efficient Yb: Er single-mode fibre laser operating at 1.56 μm. This laser has been pumped using miniature Nd : YAG and Nd : YLF lasers operating at 1.064 μm and at 1.053 μm, respectively, each of which was pumped using a 500 mW laser diode. At 1064 μm (1.053 μm) the fibre laser showed a launched threshold and slope efficiency of 13.5mW (8.5mW) and 3 1% (5.0%), respectively, with a total power output at 1.56 μm of 0.75mW (0.33mW).
Bevelled-microlensed taper connectors for laser and fibre coupling with minimal back-reflections
- Author(s): H.M. Presby and A. Benner
- Source: Electronics Letters, Volume 24, Issue 18, p. 1162 –1163
- DOI: 10.1049/el:19880789
- Type: Article
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A new means for coupling single-mode fibre to semiconductor lasers with efficiencies than 60% and back-reflections below − 60 dB is demonstrated. The method consists of utilising a CO2-laser-microlensed, expanded-beam, bevelledtaper connector. This connector design also serves to eliminate back-reflections wherever it is used in a fibre system as an interconnection element.
Performance analysis of stop-and-wait arq schemes with compound detection
- Author(s): R. Fantacci
- Source: Electronics Letters, Volume 24, Issue 18, p. 1163 –1164
- DOI: 10.1049/el:19880790
- Type: Article
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The letter is concerned with the performance analysis of different stop-and-wait ARQ schemes with repeated transmissions and compound detection (CSW). In particular, a performance comparison between partial and full use of all the information gained at the receiver to perform a decision on a block is given.
Analysis of radiation characteristics of NRD guide leaky-wave antenna by spatial network method
- Author(s): K. Terashima ; N. Yoshida ; I. Fukai
- Source: Electronics Letters, Volume 24, Issue 18, p. 1164 –1166
- DOI: 10.1049/el:19880791
- Type: Article
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In the letter the electromagnetic field in the NRD guide leaky-wave antenna is simulated by the spatial network method. The propagating constants of the leaky-wave mode and the radiation pattern are presented here.
Radiation performance of PCVD SM fibres
- Author(s): R.L.M. Lambrichs and P. Matthijsse
- Source: Electronics Letters, Volume 24, Issue 18, p. 1166 –1167
- DOI: 10.1049/el:19880792
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Radiation induced loss recovery and saturation data are presented and discussed for PCVD production and experimental pure silica core single-mode fibres.
Power spectral density of M-ary CPSK signals transmitted through nonlinear channels using an RF lineariser
- Author(s): O. Gemikonakli and A.H. Aghvami
- Source: Electronics Letters, Volume 24, Issue 18, p. 1167 –1169
- DOI: 10.1049/el:19880793
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Power spectral densities of 8-and 16-ary CPSK signals are studied by analytical means. The transmission medium considered is a nonlinear channel. The effect of an RF lineariser on PSDs is also examined.
Evaluation of HF multipath propagation effects on a novel data transmission scheme
- Author(s): Y.O. Al-Jalili
- Source: Electronics Letters, Volume 24, Issue 18, p. 1169 –1170
- DOI: 10.1049/el:19880794
- Type: Article
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The performance of a novel bandlimited signal with independent AM and PM channels over an HF radio link is considered. A model HF link simulator consisting of two independent Rayleigh fading skywaves is described. Computer simulation is used to generate test signals, and some results associated with crosstalk effects are presented.
Some designs and a characterisation method for GaAs operational amplifiers for switched-capacitor applications
- Author(s): C. Toumazou and D.G. Haigh
- Source: Electronics Letters, Volume 24, Issue 18, p. 1170 –1172
- DOI: 10.1049/el:19880795
- Type: Article
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A differential to single-ended convertor stage suitable for N-channel depletion-mode GaAs MESFET implementation is modified to allow increased gain. This enhanced input stage is combined with two different high-gain stages to yield two operational amplifier designs suitable for switched capacitor applications. A new procedure for characterising amplifiers in terms of settling time is presented and applied to the above designs. It reveals the ultimate speed limitation for a given amplifier design and allows the MESFET gate widths to be scaled to obtain optimum settling behaviour for any given capacitative load.
Line-narrowing of injection lasers due to Rayleigh backscattering from optical fibre ring interferometer
- Author(s): A.B. Bulushev ; E.M. Dianov ; A.V. Kuznetsov ; O.G. Okhotnikov
- Source: Electronics Letters, Volume 24, Issue 18, p. 1172 –1173
- DOI: 10.1049/el:19880796
- Type: Article
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Linewidth reduction and frequency-hopping for a semiconductor laser due to Rayleigh backscattering from a fibre ring interferometer have been observed. The significant decrease of the frequency-hopping range caused by the resonant nature of such backscattering is shown.
Extended-range interferometry using a coherence-tuned, synthesised dual-wavelength technique with multimode fibre links
- Author(s): D.J. Webb ; J.D.C. Jones ; D.A. Jackson
- Source: Electronics Letters, Volume 24, Issue 18, p. 1173 –1175
- DOI: 10.1049/el:19880797
- Type: Article
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We describe in the letter a technique for making extended-range interferometric measurements with a coherence multiplexed system by means of a variation on the dual-wavelength technique. The interferometer is illuminated with a single source and the two wavelengths are synthesised at the output by means of an interference filter.
Reliability of λ/4-shifted DFB lasers fabricated on a mass-production basis
- Author(s): H. Wakabayashi ; S. Akiba ; Y. Matsushima ; S. Yamamoto
- Source: Electronics Letters, Volume 24, Issue 18, p. 1175 –1176
- DOI: 10.1049/el:19880798
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The reliability of quarter wavelength shifted DFB lasers has been evaluated by long-term tests of 230 samples fabricated on a mass-production basis. Very stable long-term side-mode suppression after 6500 hour operation, and a failure rate of less than 34 fits were confirmed.
Simplified realisation method of modified spatial smoothing technique
- Author(s): S. Park and C.K. Un
- Source: Electronics Letters, Volume 24, Issue 18, p. 1176 –1177
- DOI: 10.1049/el:19880799
- Type: Article
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We present an implementation method of the modified spatial smoothing technique. Because the proposed scheme avoids forming covariance matrices, it can be easily combined with a parallel algorithm, while preserving the numerical stability. Owing to the increased effective aperture, the method performs well even in the near-field scattering environment.
Wideband direct-coupled differential amplifiers utilising AlGaAs/GaAs HBTs
- Author(s): H. Nakajima ; Y. Yamauchi ; T. Ishibashi
- Source: Electronics Letters, Volume 24, Issue 18, p. 1178 –1179
- DOI: 10.1049/el:19880800
- Type: Article
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1178
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Wideband direct-coupled differential amplifiers utilising AlGaAs/GaAs HBTs are presented. In the new circuit, input and output voltages of 0 V are obtained in a balanced condition, which allows direct cascade connections of the amplifiers. Superior amplifier performance of 20 dB gain with a 9 GHz bandwidth is obtained.
VLSI architecture for high-speed rank and median filtering
- Author(s): B. Arambepola
- Source: Electronics Letters, Volume 24, Issue 18, p. 1179 –1180
- DOI: 10.1049/el:19880801
- Type: Article
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1179
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A VLSI architecture is presented for high-speed ID and multidimensional rank filtering. The filter also provides the location of the output sample in the input data window. The rank, size and shape of the filter are variable.
Small-signal impedance of GaAs-AlxGa1−x as resonant tunnelling heterostructures at microwave frequency
- Author(s): D. Lippens and P. Mounaix
- Source: Electronics Letters, Volume 24, Issue 18, p. 1180 –1181
- DOI: 10.1049/el:19880802
- Type: Article
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1180
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The microwave impedance of high current drivability GaAs-AlxGa1−x As resonant tunnelling heterostructures in negative differential resistance conditions is measured. Using an equivalent circuit model that accounts for the frequency variation of the impedance, circuit elements corresponding to physical phenomena present in the device are identified.
High-power and fundamental-mode oscillating flared sba lasers
- Author(s): K. Shigihara ; T. Aoyagi ; S. Hinata ; Y. Nagai ; Y. Mihashi ; Y. Seiwa ; K. Ikeda ; W. Susaki
- Source: Electronics Letters, Volume 24, Issue 18, p. 1182 –1183
- DOI: 10.1049/el:19880803
- Type: Article
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p.
1182
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Flared SBA lasers with a flared waveguide are investigated. A single-lobed far-field pattern (FFP) parallel to the junction in CW oscillation at 25°C is maintained up to 80 mW.
New synthetic high coding using edge sharpening
- Author(s): S.-H. Jung and N.-C. Kim
- Source: Electronics Letters, Volume 24, Issue 18, p. 1183 –1184
- DOI: 10.1049/el:19880804
- Type: Article
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p.
1183
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A new synthetic high coding is presented for high data compression. In this scheme, only the lowpass image is transmitted, which is composed of the low-frequency components of an image, through subsampling and adaptive transform coding (ATC). Then it is expanded by interpolation at the receiver. The highpass image is simply synthesised without any overhead information by edge-sharpening the expanded lowpass image. The result of the proposed scheme shows acceptable image quality even at a high compression ratio of about 30:1
Novel design of wide-angle single-mode symmetric y-junctions
- Author(s): W.Y. Hung ; H.P. Chan ; P.S. Chung
- Source: Electronics Letters, Volume 24, Issue 18, p. 1184 –1185
- DOI: 10.1049/el:19880805
- Type: Article
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p.
1184
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We report a novel design for symmetric Y-junctions using two abrupt-bend structures with relatively large tilt angles. The proposed Y-junction has a relatively low refractive index region operating as a phase-front accelerator and is shown to have loss significantly reduced in comparison with a conventional Y-junction with a large branching angle.
Temperature and carrier injection-dependent characteristics of bulk unipolar (barrier) switches
- Author(s): A. Al-Bustani
- Source: Electronics Letters, Volume 24, Issue 18, p. 1185 –1187
- DOI: 10.1049/el:19880806
- Type: Article
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p.
1185
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The current/voltage characteristics of two-state homojunction barrier devices between 270 K and 330 K were investigated. Two new gated regenerative switching devices (the gated camel switch and the gatedpplane barrier switch) are introduced for the first time. Carrier injection-dependent operational parameters, including switching voltageVsw, switching current densityJsw, holding voltageVHand holding current densityJHwere studied. It is found that with increasing the injected electron or hole current density,Vswdecreases whileJswincreases. The two holding point parametersVHandJHremain constant over the carrier injection range. A comparison between theoretical and available experimental results is also presented.
Attenuation in melting layer of precipitation
- Author(s): W. Klaassen
- Source: Electronics Letters, Volume 24, Issue 18, p. 1187 –1188
- DOI: 10.1049/el:19880807
- Type: Article
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p.
1187
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A model of the melting layer is employed on radar measurements to simulate the attenuation of radio waves at 12, 20 and 30 GHz. The attenuation in the melting layer is simulated to be slightly larger than that of rain with the same path length and precipitation intensity. The result appears to depend on the maximum reflectivity in the melting layer.
Reflector antenna distortion compensation by array feeds: an experimental verification
- Author(s): Y. Rahmat-Samii
- Source: Electronics Letters, Volume 24, Issue 18, p. 1188 –1190
- DOI: 10.1049/el:19880808
- Type: Article
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1188
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Reflector antennas are subject to surface distortions which may result from thermal or gravitational effects. Surface distortions degrade antenna performance by reducing gain and introducing high sidelobe levels. In the letter, results of an experimental study have been presented to demonstrate how effectively a properly excited array feed in the focal plane of the reflector antenna can compensate for the undesirable effects of slowly varying surface distortions. The applicationof the array compensation concept could prove to be very useful for future large space or ground antennas.
Observation of intrinsic bistability in resonant tunnelling devices
- Author(s): E.S. Alves ; L. Haves ; M. Henini ; O.H. Hughes ; M.L. Leadbeater ; F.W. Sheard ; G.A. Toombs ; G. Hill ; M.A. Pate
- Source: Electronics Letters, Volume 24, Issue 18, p. 1190 –1191
- DOI: 10.1049/el:19880809
- Type: Article
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We report the first unambiguous observation of intrinsic bistability due to space charge build-up in an asymmetric GaAs/(AlGa)As double-barrier resonant tunnelling device.
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