Your browser does not support JavaScript!
http://iet.metastore.ingenta.com
1887
banner image
image of Volume 27, Issue 3
Online ISSN 1350-911X Print ISSN 0013-5194

Electronics Letters

Volume 27, Issue 3, 31 January 1991

Volumes & issues:

Volume 27, Issue 3

31 January 1991

Automatic gain control in cascaded erbium doped fibre amplifier systems
  • Author(s): A.D. Ellis ; R.M. Percival ; A. Lord ; W.A. Stallard
  • Source: Electronics Letters, Volume 27, Issue 3, p. 193 –195
  • DOI:  10.1049/el:19910125
  • Type: Article
  • + Show details - Hide details
  • p. 193 –195 (3)
    Automatic gain control for erbium doped fibre amplifiers is achieved via active stabilisation of the amplifier output power. This technique automatically compensates for any changes in the amplifier gain caused by local environmental and optical effects. Output power is also stabilised for changes in optical input signal, allowing for a full 5 dB repair margin per link in long span systems.
    Add to favourites
    Export citations
Electro-optically tunable wavelength demultiplexer using depressed index waveguides
  • Author(s): M. López-amo ; R. Subías ; J.M. López-higuera ; M.A. Muriel
  • Source: Electronics Letters, Volume 27, Issue 3, p. 195 –196
  • DOI:  10.1049/el:19910126
  • Type: Article
  • + Show details - Hide details
  • p. 195 –196 (2)
    A novel configuration of an integrated optical tunable wavelength demultiplexer with a stable channel spacing is proposed. The structure consists of a three-mode depressed index diffused waveguide with single-mode input and output waveguides. The refractive index depression has been designed using experimental data of double diffusion of MgO on Ti:LiNbO3 waveguides. The BPM simulation of the structure supports the feasibility of the device and shows a good wavelength tunability.
    Add to favourites
    Export citations
Distortion-free amplification of high-speed test patterns up to 100 Gbit/s with erbium-doped fibre amplifiers
  • Author(s): H. Izadpanah ; D. Chen ; Lin Chinlon ; M.A. Saifi ; W.I. Way ; A. Yi-Yan ; J.L. Gimlett
  • Source: Electronics Letters, Volume 27, Issue 3, p. 196 –198
  • DOI:  10.1049/el:19910127
  • Type: Article
  • + Show details - Hide details
  • p. 196 –198 (3)
    A report is made on the first distortion-free optical amplification of high-speed signals up to100 Gbit/s in an erbium-doped fibre amplifier. The amplifier's high-speed temporal characteristics were measured and compared with those of a semiconductor optical amplifier. The high-speed optical test patterns (repetitive or modulated) were generated from a gain-switched DFB laser using optical spectral filtering, chirp compression and optical time-division multiplexing.
    Add to favourites
    Export citations
1×2 lossless semiconductor optical switch
AlGaAs–GaAs–InGaAs strained layer laser structure with performance independent of AlGaAs layer quality
  • Author(s): S. Xin ; K.F. Longenbach ; W.I. Wang
  • Source: Electronics Letters, Volume 27, Issue 3, p. 199 –201
  • DOI:  10.1049/el:19910129
  • Type: Article
  • + Show details - Hide details
  • p. 199 –201 (3)
    An AlGaAs–GaAs–InGaAs strained layer laser structure has been shown to have a low threshold current density which is independent of AlGaAs layer quality. This threshold invariance is attributed to the use of a large GaAs region outside the InGaAs well to reduce the effects of traps in the AIGaAs on the active region of the laser and was demonstrated by characterising identical structures grown by molecular beam epitaxy (MBE) under different AIGaAs growth conditions. These results should have strong implications for the reliability and manufacturability of such lasers and for the integration with electronic devices where low temperature growth is required.
    Add to favourites
    Export citations
2-D DCT systolic array implementation
Buried stacked insulator: new soi-structure formed by ion beam synthesis
Optical sampling oscilloscope using nonlinear fibre loop mirror
Simple frequency/voltage convertor with low output ripple
Current sensing by mode coupling in fibre via the Faraday effect
Anomalous temporal response of gain guided surface emitting lasers
  • Author(s): N.K. Dutta ; L.W. Tu ; G. Hasnain ; G. Zydzik ; Y.H. Wang ; A.Y. Cho
  • Source: Electronics Letters, Volume 27, Issue 3, p. 208 –210
  • DOI:  10.1049/el:19910135
  • Type: Article
  • + Show details - Hide details
  • p. 208 –210 (3)
    Under pulsed operation, gain guided surface emitting lasers have exhibited long delay times and higher threshold current than for CW operation. This phenomenon is explained by assuming that adiabatic heating of the active region results in time evolution of the transverse mode guiding. Our theory suggests that a built in index guiding greater than 10-2 will stabilise the fundamental mode and improve the temporal performance of surface emitting lasers.
    Add to favourites
    Export citations
Optical amplification in a nonlinear fibre interferometer
High gain limiting erbium-doped fibre amplifier with over 30 dB dynamic range
  • Author(s): W.I. Way ; D. Chen ; M.A. Saifi ; M.J. Andrejco ; A. Yi-Yan ; A. von Lehman ; C. Lin
  • Source: Electronics Letters, Volume 27, Issue 3, p. 211 –213
  • DOI:  10.1049/el:19910137
  • Type: Article
  • + Show details - Hide details
  • p. 211 –213 (3)
    A limiting optical amplifier is demonstrated using three cascaded stages of erbium-doped fibre amplifiers. A constant output power of +12.9 dBm was obtained for an input power ranging from −30 to 1.5 dBm. The optical noise figure of the amplifier has been measured over the >30 dB dynamic range. Design guidelines for optical limiting amplifiers are also presented.
    Add to favourites
    Export citations
W-band monolithic frequency doubler using vertical GaAs varactor diode with n+ buried layer
  • Author(s): G. Hegazi ; A. Ezzeddine ; F. Phelleps ; P. Mcnally ; K. Pande ; P. Rice ; P. Pages
  • Source: Electronics Letters, Volume 27, Issue 3, p. 213 –214
  • DOI:  10.1049/el:19910138
  • Type: Article
  • + Show details - Hide details
  • p. 213 –214 (2)
    A W-band monolithic frequency doubler was designed and fabricated using a vertical GaAs varactor diode that has an n+ buried layer and uses a mesa isolation process. An output power of 30 mW was obtained from this chip at 93 GHz with a conversion efficiency of 12%. This is believed to be the first reported W-band monolithic varactor diode frequency doubler.
    Add to favourites
    Export citations
Automatic adjustment of quadrature modulators
Cascadable laser logic devices: discrete integration of phototransistors with surface-emitting laser diodes
  • Author(s): G.R. Olbright ; R.P. Bryan ; K. Lear ; T.M. Brennan ; G. Poirier ; Y.H. Lee ; J.L. Jewell
  • Source: Electronics Letters, Volume 27, Issue 3, p. 216 –217
  • DOI:  10.1049/el:19910140
  • Type: Article
  • + Show details - Hide details
  • p. 216 –217 (2)
    A new class of cascadable optical logic devices is described which consists of integrated GaAs/AlGaAs phototransistors and surface-emitting lasers. The devices function as optical neurons (‘smart pixels’), have high optical gain (a factor of >20 overall, >200 differential), very high on/off contrast (>2700, 34dB) and are ideal for neural networks and optical computing applications.
    Add to favourites
    Export citations
Time domain measurements of launching-condition-dependent bandwidth of all-plastic optical fibres
Efficient pulse compressor for golay complementary sequences
  • Author(s): S.Z. Budišin
  • Source: Electronics Letters, Volume 27, Issue 3, p. 219 –220
  • DOI:  10.1049/el:19910142
  • Type: Article
  • + Show details - Hide details
  • p. 219 –220 (2)
    The highly regular structure of binary Golay complementary sequences of length 2N makes possible a very simple correlator for these sequences. The algorithm called fast Golay correlation (FGC) performs the correlation of the input radar signal with the Golay sequence using only 2.log2(M) operations per input sample as opposed to M operations required by standard correlators. This algorithm is also valid for complex sequences of the same length. This fast correlator and the good autocorrelation properties of Golay sequences make them the ideal choice for high speed, long sequence pulse compression. Sequence agility on the pulse to pulse basis is also possible at the expense of some added complexity.
    Add to favourites
    Export citations
Cyclic wavelength jitter in actively mode-locked semiconductor lasers
Nonlinear, dispersion-free 10 GHz optical pulse train transmission in distributed erbium-doped fibre
  • Author(s): D.M. Spirit ; I.W. Marshall ; P.D. Constantine ; D.L. Williams ; S.T. Davey ; B.J. Ainslie
  • Source: Electronics Letters, Volume 27, Issue 3, p. 222 –224
  • DOI:  10.1049/el:19910144
  • Type: Article
  • + Show details - Hide details
  • p. 222 –224 (3)
    The transmission of a 10 GHz repetition rate optical pulse train over a 28.5 km long distributed erbium-doped fibre amplifier is reported. In the linear dispersion regime, the pulses broaden so that the tails of adjacent pulses overlap. However, given sufficiently high signal powers, the optical Kerr effect causes pulse narrowing back to the original 18 ps pulsewidth.
    Add to favourites
    Export citations
Recursive construction of polynomial with prescribed phase on unit circle
Multidimensional multirate filters derived from one dimensional filters
Cryptanalysis of public-key distribution systems based on Dickson polynomials
  • Author(s): Da-Xing Li
  • Source: Electronics Letters, Volume 27, Issue 3, p. 228 –229
  • DOI:  10.1049/el:19910147
  • Type: Article
  • + Show details - Hide details
  • p. 228 –229 (2)
    Yang Yi-Xian presented a public-key distribution system based on Dickson polynomials. Varadharajan commented on it2 and showed that the choice of parameters of such a system is quite significant in its design. In this Letter, it is pointed out, by analysing the computational complexity of this system, that this system is insecure no matter how the system parameters are chosen and no matter how the Dickson polynomials are calculated.
    Add to favourites
    Export citations
Single-frequency travelling-wave erbium-doped fibre loop laser
Application of rare-earth doped fibres as lowpass filters in passive optical networks
  • Author(s): I.J. Wilkinson ; T. Finegan ; B.J. Ainslie
  • Source: Electronics Letters, Volume 27, Issue 3, p. 230 –232
  • DOI:  10.1049/el:19910149
  • Type: Article
  • + Show details - Hide details
  • p. 230 –232 (3)
    In the passive optical networks currently under study, it is necessary to provide high attenuation of the 1500–1600nm fibre window in front of the telephony receiver and transmitter. A cheap, simple filter is required which also has low loss at 1300nm. Fibres doped with suitable concentrations of the rare-earth ions, erbium and neodymium are shown to have spectral attenuation characteristics ideal for this application.
    Add to favourites
    Export citations
Effect of nonlinear gain on intensity noise in single-mode semiconductor lasers
  • Author(s): G.P. Agrawal
  • Source: Electronics Letters, Volume 27, Issue 3, p. 232 –234
  • DOI:  10.1049/el:19910150
  • Type: Article
  • + Show details - Hide details
  • p. 232 –234 (3)
    The effect of nonlinear gain on the intensity noise of semiconductor lasers is studied by solving the single-mode rate equation with the Langevin noise term. The analytic expressions for the relative intensity noise and the intensity autocorrelation function are obtained by using a form of the nonlinear gain that is valid even at high operating power levels. These are used to obtain a simple expression for the signal-to-noise ratio (SNR) of the laser output. The SNR is found to saturate to a limiting value of about 30dB at high powers because of the nonlinear-gain effects related to intraband gain saturation.
    Add to favourites
    Export citations
Balanced tuned receiver front end with low noise and high common mode rejection ratio
  • Author(s): N.G. Jensen ; E. Bødtker ; G. Jacobsen ; S. Søensen
  • Source: Electronics Letters, Volume 27, Issue 3, p. 234 –235
  • DOI:  10.1049/el:19910151
  • Type: Article
  • + Show details - Hide details
  • p. 234 –235 (2)
    A balanced optical receiver front-end suitable for Gbit/s heterodyne detection in coherent optical communication systems is presented. The transimpedance is 70dBΩ with ±2dB ripple over the passband from 2 to 4.4 GHz. The ripple was reduced to ±0.5 dB within a passband from 2.1 to 4.4 GHz by manual tuning of the circuit. The equivalent input noise spectral density is below 4pA/√(Hz) and the common mode rejection ratio better than 26 dB. Standard commercial photodiodes and packaged components are used, and the circuit is implemented in conventional printed circuit board techniques.
    Add to favourites
    Export citations
InGaAs/InP-Photodiodes with dark current limited by generation-recombination
  • Author(s): F. Buchali ; R. Behrendt ; G. Heymann
  • Source: Electronics Letters, Volume 27, Issue 3, p. 235 –237
  • DOI:  10.1049/el:19910152
  • Type: Article
  • + Show details - Hide details
  • p. 235 –237 (3)
    From I(V) and C(V) measurements the conclusion is made that among the sources of dark current in InGaAs/lnP diodes, generation-recombination current dominates. Four different contributions to the dark from material layers have been identified. The highest generation rate was observed in the InP buffer layer. Various traps causing the dark current in these different layers have also been identified.
    Add to favourites
    Export citations
Concatenated soliton fibre link
Microlens arrays for interconnection of singlemode fibre arrays
Design and characteristics of ring-slot type FSS
10 Gbit/s low chirp performance of strained layer multiquantum well DFB laser
  • Author(s): Y. Hirayama ; M. Morinaga ; M. Tanimura ; M. Onomura ; M. Funemizu ; M. Kushibe ; N. Suzuki ; M. Nakamura
  • Source: Electronics Letters, Volume 27, Issue 3, p. 241 –243
  • DOI:  10.1049/el:19910156
  • Type: Article
  • + Show details - Hide details
  • p. 241 –243 (3)
    A large improvement in the high speed characteristic of strained layer multiquantum well (MQW) DFB lasers with a selfaligned constricted mesa structure is described. A very low chirp of 4.2Å at 10 Gbit/s was obtained due to an increased differential gain as large as 4.6×10−l2m3/s and a reduced α parameter less than 2.
    Add to favourites
    Export citations
Thin wire antennas in chiral media
  • Author(s): D.L. Jaggard ; J.C. Liu ; A. Grot ; P. Pelet
  • Source: Electronics Letters, Volume 27, Issue 3, p. 243 –244
  • DOI:  10.1049/el:19910157
  • Type: Article
  • + Show details - Hide details
  • p. 243 –244 (2)
    By immersing conducting wire antennas in chiral media, their radiation characteristics can be tailored and enhanced. As the chirality of the media or length of the wire is increased, current along such antennas is characterised by a decaying rather than sinusoidal distribution. This produces reduced sidelobes, decreased main lobe beamwidths, and forbidden zones in the radiation pattern.
    Add to favourites
    Export citations
Totally integrated erbium fibre soliton laser pumped by laser diode
Optically-controlled grating switch (OG-SW)
Performance characteristics of CSMA/CD for fibre optic networks
High performance balanced heterodyne front end using special fibre coupling scheme
Exact acoustic leaky wave solutions for single-mode fibres
First microwave characterisation of LP-MOCVD grown GaInP/GaAs self-aligned HBT
  • Author(s): S.L. Delage ; M.A. Di Forte-Poisson ; H. Blanck ; C. Brylinski ; E. Chartier ; P. Collot
  • Source: Electronics Letters, Volume 27, Issue 3, p. 253 –254
  • DOI:  10.1049/el:19910163
  • Type: Article
  • + Show details - Hide details
  • p. 253 –254 (2)
    The microwave characterisation of GaInP/GaAs HBTs is reported. The structures are grown by LP-MOCVD, and carbon base doping is used. The transistor design is basically multimesas and the devices are obtained using a combination of dry and wet etching. The current and power gain cutoff frequencies of these devices are, respectively, 30 GHz and 45 GHz.
    Add to favourites
    Export citations
Complementary sets of chirp-like polyphase sequences
  • Author(s): B.M. Popović
  • Source: Electronics Letters, Volume 27, Issue 3, p. 254 –255
  • DOI:  10.1049/el:19910164
  • Type: Article
  • + Show details - Hide details
  • p. 254 –255 (2)
    A new construction for the complementary sets of polyphase sequences is presented. The new construction is based on the application of Zadoff—Chu, as well as Ipatov polyphase sequences with ideal periodic autocorrelation function. It is shown that cyclic time shifted versions of either polyphase sequences form the complementary set, if the length of sequences is N = 5. m2 and the corresponding time shifts are different multiples of m, where s and m are any positive integers.
    Add to favourites
    Export citations
Design of erbium doped fibre amplifiers for 980 nm or 1480 nm pumping
Increased optical saturation intensities in GaInAs multiple quantum wells by the use of AlGaInAs barriers
  • Author(s): T.H. Wood ; T.Y. Chang ; J.Z. Pastalan ; C.A. Burrus ; N.J. Sauer ; B.C. Johnson
  • Source: Electronics Letters, Volume 27, Issue 3, p. 257 –259
  • DOI:  10.1049/el:19910166
  • Type: Article
  • + Show details - Hide details
  • p. 257 –259 (3)
    Quaternary AlGaInAs is demonstrated to be an excellent barrier material for long-wavelength quantum well modulators. In addition to lower trap density than ternary AlInAs, the low valence-band discontinuity results in saturation intensities at least a factor of 30 higher than InGaAs wells with InP barriers. Decreasing barrier thicknesses increases saturation intensities by an additional factor of 5.
    Add to favourites
    Export citations
Fading reduction in LOS microwave links due to path inclination
  • Author(s): M.V.S.N. Prasad ; S.K. Sarkar ; H.N. Dutta ; B.M. Reddy
  • Source: Electronics Letters, Volume 27, Issue 3, p. 259 –261
  • DOI:  10.1049/el:19910167
  • Type: Article
  • + Show details - Hide details
  • p. 259 –261 (3)
    Investigations of the effect of path inclination on multipath fading caused by super-refractive layers and ducts, based on the data collected from various LOS links over the Indian subcontinent are reported. It is observed that as the path inclination increases, deep fades caused by layers and ducts get reduced. In regions where layers and ducts prevail for a considerable percentage of time, the design of LOS links should incorporate the concept of path inclination to overcome fading.
    Add to favourites
    Export citations
High power, compact 1.48 μm diode-pumped broadband superfluorescent fibre source at 1.5 μm
Comparison of bulk buried heterostructure and multiple quantum well laser amplifier switches
  • Author(s): B.P. Cavanagh ; I.W. Marshall ; G. Sherlock ; H. Wickes
  • Source: Electronics Letters, Volume 27, Issue 3, p. 263 –265
  • DOI:  10.1049/el:19910169
  • Type: Article
  • + Show details - Hide details
  • p. 263 –265 (3)
    Multiple quantum well (MQW) and bulk laser amplifier switches are directly compared by analysis of the switching speed and the wavelength dependence of contrast (extinction ratio) and noise. The MQW device is found to be three times faster, with 20dB less contrast and 12.5dB less loss at optimum wavelength. It is thus shown that MQW devices are more suitable for use as fast switches.
    Add to favourites
    Export citations
Tracking a manoeuvring target with correlated measurement noises by manoeuvre detection method
High performance hybrid circuit modules for lightwave systems operating at data rates of 10 Gbit/s and higher
Ku-band high efficiency high gain pseudomorphic HEMT
Waveguide optical polarisation splitter with Langmuir-Blodgett cladding layer
Beamforming in presence of element failure
  • Author(s): M.H. Er  and  S.K. Hui
  • Source: Electronics Letters, Volume 27, Issue 3, p. 273 –275
  • DOI:  10.1049/el:19910174
  • Type: Article
  • + Show details - Hide details
  • p. 273 –275 (3)
    A simple and effective algorithm to regain sidelobe suppression lost due to element failure with narrowest possible beam-width is presented. The formulation results in a constrained optimisation problem involving a quadratic constraint and a set of linear constraints on the weights. An efficient numerical technique to obtain the optimal weights is presented. Numerical results are presented to illustrate the performance achievable.
    Add to favourites
    Export citations
Generation of learning neighbourhood in Kohonen feature maps by means of simple nonlinear network
Evaluation of Gram matrix off-diagonal elements using system time moments
10 Gbit/s bipolar laser driver
Interelectrode capacitance nonlinearities in vertical power DMOSFETs
  • Author(s): K. Shenai
  • Source: Electronics Letters, Volume 27, Issue 3, p. 280 –282
  • DOI:  10.1049/el:19910178
  • Type: Article
  • + Show details - Hide details
  • p. 280 –282 (3)
    Extensive numerical simulations were performed to understand interelectrode capacitance characteristics of vertical power DMOSFETs. Two-dimensional simulations indicate large capacitance-voltage nonlinearities, especially for the gate-to-drain Miller capacitance Cgd. Capacitance-voltage characteristics are explained in terms of a simple equivalent circuit that relates each capacitance component to its physical origin.
    Add to favourites
    Export citations
Adaptive filtering using modified fermat number transform
High efficiency and low sidelobe shaped Cassegrain twist reflector antenna with four-horn triple-mode monopulse feed
  • Author(s): D.C. Chang ; Y.C. Chen ; M.S. Yuan
  • Source: Electronics Letters, Volume 27, Issue 3, p. 284 –285
  • DOI:  10.1049/el:19910180
  • Type: Article
  • + Show details - Hide details
  • p. 284 –285 (2)
    A high efficiency and low sidelobe shaped Cassegrain twist reflector antenna with four-horn triple-mode monopulse feed is synthesised. The far-field radiation pattern of the main reflector is specified by the desired Taylor pattern with n̅ = 6 and the design peak sidelobe level of –25dB. A four-horn triple-mode monopulse feed is designed and fabricated. A polarisation twisting technique is applied to the shaped Cassegrain antenna for reducing the blocking of the main aperture by the subreflector. The aperture efficiency can be raised to about 79%.
    Add to favourites
    Export citations
Parallel FFT algorithms for mimd computers
  • Author(s): M.K. Fung  and  A.K. Nandi
  • Source: Electronics Letters, Volume 27, Issue 3, p. 286 –288
  • DOI:  10.1049/el:19910181
  • Type: Article
  • + Show details - Hide details
  • p. 286 –288 (3)
    Two methods of computing the FFT (fast Fourier transform) concurrently by multiple computers are presented. Both methods have been implemented on a set of transputers. The first method runs on a simple cyclic network, whereas the second one requires a hypercube configuration. Based on simulations and analysis, their relative advantages and disadvantages in terms of speed-up performance, memory requirement, and host participation are discussed.
    Add to favourites
    Export citations
Void elimination by lateral gap diffusion in silicon direct bonding (SDB) technology
Broadband measurements of frequency noise spectrum in two section DBR laser
  • Author(s): E. Goobar  and  R. Schatz
  • Source: Electronics Letters, Volume 27, Issue 3, p. 289 –291
  • DOI:  10.1049/el:19910183
  • Type: Article
  • + Show details - Hide details
  • p. 289 –291 (3)
    The dependence of the frequency noise on the output power, the tuning current and the current modulation has been measured in a two electrode DBR laser from 30MHz to 8GHz. The frequency noise spectrum was fairly flat and decreased with increased output power at a rate faster than l/P. At certain biasing levels, the noise increased and the relaxation peak was shifted towards lower frequencies when current was injected into the passive waveguide. Furthermore, the frequency noise was not affected by the current modulation.
    Add to favourites
    Export citations
Null synthesis for shaped reflector antennas
  • Author(s): A.D. Monk ; P.J.B. Clarricoats ; Zhou Hai
  • Source: Electronics Letters, Volume 27, Issue 3, p. 291 –293
  • DOI:  10.1049/el:19910184
  • Type: Article
  • + Show details - Hide details
  • p. 291 –293 (3)
    Some preliminary results are presented, demonstrating the feasibility of synthesising reflector profiles to produce deep nulls in the radiation pattern at prescribed angles while maintaining high gain levels at other prescribed angles. The synthesis technique can be applied to both shaped rigid and reconfigurable mesh reflector antennas. Experimental results for an 85cm mesh reflector antenna at 10GHz are included to provide validation of the technique.
    Add to favourites
    Export citations
Improving performance of multidestination ARQ schemes under high error rate conditions
Frequency assignment for satellite multilevel SCPC systems

Most viewed content for this Journal

Article
content/journals/el
Journal
5
Loading

Most cited content for this Journal

Print this page
This is a required field
Please enter a valid email address