Online ISSN
1350-911X
Print ISSN
0013-5194
Electronics Letters
Volume 18, Issue 19, 16 September 1982
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Volume 18, Issue 19
16 September 1982
High-efficiency short-cavity InGaAsP laser with one high-reflectivity mirror
- Author(s): T.P. Lee ; C.A. Burrus ; P.L. Liu ; A.G. Dentai
- Source: Electronics Letters, Volume 18, Issue 19, p. 805 –806
- DOI: 10.1049/el:19820547
- Type: Article
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High differential quantum efficiency (70%), high output power (5 mW), and stable single-frequency output at high (1 Gbit/s) modulation rates have been obtained experimentally using short-cavity InGaAsP injection lasers with a metallic mirror on one facet only.
Auger recombination rate in InGaAsP lasers
- Author(s): M.G. Burt
- Source: Electronics Letters, Volume 18, Issue 19, p. 806 –807
- DOI: 10.1049/el:19820548
- Type: Article
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For the Auger recombination rate in InGaAsP there is an order of magnitude discrepancy between the measurements by Su et al. and the calculations by Dutta and Nelson, and Sugimura. It is suggested that a major source of this discrepancy is the method used to calculate the overlap integrals. A calculation that supports this suggestion is described.
Exact design of elliptic switched-capacitor filters by synthesis
- Author(s): J. Taylor
- Source: Electronics Letters, Volume 18, Issue 19, p. 807 –809
- DOI: 10.1049/el:19820549
- Type: Article
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–809
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The application of exact design by synthesis to elliptical switched-capacitor lowpass ladder filters of the lossless discrete integrator (LDI) type is described.
Fabrication and evaluation of MCVD single-mode fibres with and without central index depression
- Author(s): B.J. Ainslie ; K.J. Beales ; D.M. Cooper ; C.R. Day
- Source: Electronics Letters, Volume 18, Issue 19, p. 809 –811
- DOI: 10.1049/el:19820550
- Type: Article
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A gas phase etching process has been developed to remove the central index depression in the cores of MCVD single-mode preforms. A comparison is made with conventional fibres of the optical loss, spot size and bending sensitivity. The results are in good agreement with the theory.
High-peak-power picosecond optical pulse generation from highly RF-modulated InGaAsP DH diode laser
- Author(s): N. Onodera ; H. Ito ; H. Inaba
- Source: Electronics Letters, Volume 18, Issue 19, p. 811 –812
- DOI: 10.1049/el:19820551
- Type: Article
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The feasibility for generating high-peak-power ultrashort optical pulses was demonstrated from a highly RF-modulated InGaAsP DC-PBH laser diode at 1.3 μm for the first time. Measured pulse width is found to be approximately 28 ps at 7 mW averaged output power, and peak output power reached about 1.2 W at 210 MHz repetition frequency. Higher peak output and shorter optical pulses could be expected with this type of semiconductor diode laser in the near-infra-red region.
Single-mode InGaAsP/InP buried waveguide structures grown on channelled {111}B InP substrates
- Author(s): T.M. Benson ; A.V. Syrbu ; N. Chand ; P.A. Houston
- Source: Electronics Letters, Volume 18, Issue 19, p. 812 –813
- DOI: 10.1049/el:19820552
- Type: Article
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InGaAsP buried waveguide structures were fabricated by LPE on channelled {111}B InP substrates. Control of the channel depth and growth time enabled waveguides of small dimensions to be produced which supported one TE and one TM polarised mode only.
Single-mode-fibre point and extended temperature sensors
- Author(s): S.J. Petuchowski ; G.H. Sigel ; T.G. Giallorenzi
- Source: Electronics Letters, Volume 18, Issue 19, p. 814 –815
- DOI: 10.1049/el:19820553
- Type: Article
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The response of single-mode fibres to time-varying thermal perturbations has been characterised by using a Mach-Zehnder interferometer. It is shown that single-mode fibres offer the possibility of high-speed, high-sensitivity remote temperature sensing with a minimum disturbance of the thermal environment and the capability to operate in an electro-magnetically active environment. In addition, fibre temperature sensors can be configured to measure not only the specific temperature at any given point, but also offer the unique feature of extended temperature measurements over the length of a fibre segment in which the device optically integrates any thermally induced fluctuations.
Low-loss lange coupler
- Author(s): J.L. Hobdell ; J.W. Biggin ; K.S. Band
- Source: Electronics Letters, Volume 18, Issue 19, p. 815 –816
- DOI: 10.1049/el:19820554
- Type: Article
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The use of air-bridge straps in place of bond wires on the Lange coupler on an alumina substrate is investigated. It is shown that the resultant coupler has lower loss when compared with a coupler using bond wires and is more suitable for mass production than the bond-wire type.
Shaped wire antennas with maximum directivity
- Author(s): D.K. Cheng and C.H. Liang
- Source: Electronics Letters, Volume 18, Issue 19, p. 816 –818
- DOI: 10.1049/el:19820555
- Type: Article
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The optimum shape of a wire antenna for maximum directivity is obtained by applying the method of moments and the simplex method for function minimisation. Antenna shape is approximated by piecewise parabolas, and the effects of wire radius on current distribution are considered.
Dispersion-free single-mode doubly clad fibres with small pure bend losses
- Author(s): P.L. Francois
- Source: Electronics Letters, Volume 18, Issue 19, p. 818 –819
- DOI: 10.1049/el:19820556
- Type: Article
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A pure bend loss formula for doubly clad profiles is used to investigate the limitations and tolerances induced in the design of dispersion-free W-fibres by keeping the radiation losses below an acceptable level.
Autocorrelation function measurements with fibre interferometers
- Author(s): K. Mochizuki
- Source: Electronics Letters, Volume 18, Issue 19, p. 820 –821
- DOI: 10.1049/el:19820557
- Type: Article
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A polarisation-maintaining single-mode-fibre interferometer is described. The combination of a stress-induced birefringent fibre and its temperature change offers an interferometer with a very accurate optical delay line. Using the interferometer the autocorrelation function of a semiconductor laser is measured directly.
7 Gbit/s coherent pulse generation in an actively mode-locked GaAlAs diode laser
- Author(s): Y. Suzuki and T. Sato
- Source: Electronics Letters, Volume 18, Issue 19, p. 821 –823
- DOI: 10.1049/el:19820558
- Type: Article
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High-rate coherent pulse generation was demonstrated with a GaAlAs laser system by active mode-locking. Almost transform-limited pulses of about 30 ps duration are obtained at a rate of about 7 GHz.
Conversion loss of an MIC balanced mixer: calculation and measurements
- Author(s): B. Schüppert
- Source: Electronics Letters, Volume 18, Issue 19, p. 823 –824
- DOI: 10.1049/el:19820559
- Type: Article
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A comparison between theory and experiment is given for an MIC balanced mixer with beam-lead Schottky-barrier diodes in the frequency range from 1 to 8 GHz.
Side-tunnel fibre: an approach to polarisation-maintaining optical waveguiding scheme
- Author(s): T. Okoshi ; K. Oyamada ; M. Nishimura ; H. Yokota
- Source: Electronics Letters, Volume 18, Issue 19, p. 824 –826
- DOI: 10.1049/el:19820560
- Type: Article
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A new type of polarisation-maintaining fibre is proposed, analysed, and preliminary fabrication and measurement are described. The new fibre features two ‘side tunnels’ bored on both sides of the core, and exhibits an absolutely single-polarisation characteristic or a relatively strong modal birefringence. The normalised birefringence obtained so far is 0.73×10−4. This value is appreciably lower than expected. Two possible reasons are discussed.
Direct method of reducing order of linear systems using koenig's theorem
- Author(s): C.P. Therapos
- Source: Electronics Letters, Volume 18, Issue 19, p. 826 –827
- DOI: 10.1049/el:19820561
- Type: Article
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Linear-system reduction is achieved by a simple and direct method based on Koenig's theorem, to approximate the stability equations of the given system. Thus the proposed technique is superior, for very high-order systems, to other methods which, yielding almost identical results, factorise the stability equations.
Serial synthesis of minimum-shift-keyed signals
- Author(s): N. Ekanayake
- Source: Electronics Letters, Volume 18, Issue 19, p. 827 –829
- DOI: 10.1049/el:19820562
- Type: Article
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A new technique for serial generation of minimum (frequency)-shift-keyed signals is proposed. The new modulator consists of a data encoder and a conventional frequency-shift-keying modulator. The theory underlying the derivation of the modulator structure is outlined.
Frequency-domain approach to model-reduction problem
- Author(s): A. Lepschy ; G. Mian ; U. Viaro
- Source: Electronics Letters, Volume 18, Issue 19, p. 829 –830
- DOI: 10.1049/el:19820563
- Type: Article
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–830
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Model reduction is performed in the frequency domain by matching the first Taylor-series-expansion coefficients of the square magnitude of the original and the approximating transfer functions at suitable frequencies. The method is computationally simple and may lead to a satisfactory approximation while preserving stability and minimum-phase characteristics.
Preparation and properties of monolithically integrated lenses on InGaAsP/InP light-emitting diodes
- Author(s): J. Heinen
- Source: Electronics Letters, Volume 18, Issue 19, p. 831 –832
- DOI: 10.1049/el:19820564
- Type: Article
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p.
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–832
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A simple chemical etching technique has been developed to prepare integrated lenses of the InP substrate material on InGaAsP/InP double-heterostructure Burrus-type diodes. By coupling lensed diodes with emitting regions 20 μm in diameter to graded-index fibres with a core diameter of 60 μm, an improvement in launching efficiency up to a factor of 3 compared to flat devices has been reproducibly achieved.
Relations between moments of index profile and moments of deflection function and phase function of optical fibre or preform
- Author(s): P.L. Chu
- Source: Electronics Letters, Volume 18, Issue 19, p. 832 –833
- DOI: 10.1049/el:19820565
- Type: Article
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This letter reports the simple relations between the moments of the refractive-index profile and the moments of the corresponding deflection function and phase function of an optical fibre or its preform. These relations enable one to measure the moments of the profile in a simple way. They can also be used for checking the reconstruction errors in the profile inversion program.
Worst-case arbitration time in S-100-type computer bus systems
- Author(s): D.M. Taub
- Source: Electronics Letters, Volume 18, Issue 19, p. 833 –835
- DOI: 10.1049/el:19820566
- Type: Article
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The computer bus systems S-100 and Fastbus use a scheme consisting of extra logic circuits in each device and extra bus lines for arbitrating rapidly between two or more devices seeking to use the bus at the same time. The letter shows how to develop a table of priority numbers that make the arbitration time a maximum, and gives an expression for this maximum time in terms of logic-circuit and bus-propagation delays.
Transferred-electron oscillations in In0.53Ga0.47As
- Author(s): Y.Y. Zhao ; C.J. Wei ; H. Beneking
- Source: Electronics Letters, Volume 18, Issue 19, p. 835 –836
- DOI: 10.1049/el:19820567
- Type: Article
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Transferred-electron oscillations were observed and investigated in planar devices of In0.53Ga0.47As. The peak-to-peak magnitude of oscillations with respect to the device current at threshold field was as high as 70%, indicating the peak-to-valley velocity ratio of 3.3:1 for this material. The domain velocity was estimated from the oscillation frequency (2 GHz) and the corresponding device length (40 μm) to be 8×106 cms−1. The results presented in the letter show a promising prospect for TED applications of this ternary alloy.
OH absorption in GeO2-doped fused silica fibres
- Author(s): A.V. Belov ; E.M. Dianov ; P.N. Lebedev ; A.N. Guryanov ; V.F. Hopin
- Source: Electronics Letters, Volume 18, Issue 19, p. 836 –837
- DOI: 10.1049/el:19820568
- Type: Article
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The OH-ion absorption of SiO2/GeO2-core step-index multimode fibres in the 1.2–1.6 μm region has been studied in relation to changing GeO2 concentrations. It was found that the OH absorption band at ̃ 1.4 μm in SiO2/GeO2-core fibres had two components with maxima at 1.39 μm and 1.42 μm related to the first overtone of the fundamental OH vibration in SiO2 and GeO2, respectively.
Spatial uniformity measurement of SAW convolvers
- Author(s): D.R. Selviah ; D.H. Warne ; D.P. Morgan
- Source: Electronics Letters, Volume 18, Issue 19, p. 837 –839
- DOI: 10.1049/el:19820569
- Type: Article
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For correlation of coded waveforms, the nonlinear interaction process in a SAW convolver should ideally give an amplitude and phase independent of position. A new experimental method of measuring this spatial uniformity used CW test waveforms and gave a resolution of 25 ns—a considerably higher resolution than previously attained.
Broadband millimetre-wave PIN-diode attenuator with double-ridge waveguide flanges
- Author(s): L.-P. Schmidt and H. Meinel
- Source: Electronics Letters, Volume 18, Issue 19, p. 839 –840
- DOI: 10.1049/el:19820570
- Type: Article
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The letter reports new results on a broadband fin-line PIN-diode attenuator furnished with double-ridge waveguide flanges. The full bandwidth capabilities of fin line can thus be utilised. The attenuation is adjustable between 2 and 35 dB over the entire frequency band from 18 to 40 GHz.
Compact matrix scheme for use in computer analysis of switched-capacitor networks
- Author(s): C. Lau and J.I. Sewell
- Source: Electronics Letters, Volume 18, Issue 19, p. 840 –841
- DOI: 10.1049/el:19820571
- Type: Article
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The matrices that normally occur in the analysis of multiphase switched-capacitor networks are quite large and very sparse. A technique is presented which reduces the matrix order and increases the fill. Storage requirements are minimised and the arithmetic handling of large arrays is reduced without recourse to sparse matrix procedures.
First-order theory of the five-port symmetrical star junction
- Author(s): A.J. Belfort and A.L. Cullen
- Source: Electronics Letters, Volume 18, Issue 19, p. 841 –842
- DOI: 10.1049/el:19820572
- Type: Article
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It is shown that, from the three conditions of (a) five-fold symmetry, (b) reciprocity and (c) freedom from loss, useful constraints can be found on the elements of the scattering matrix of a symmetrical five-port star junction. These constraints can be used to set limits to the possible positions qi, of the centres of the q-circles when the five-port junction is used as an element in a six-port reflectometer.
Monomode fibre with ultra-low loss and minimum dispersion at 1.55 μm
- Author(s): B.J. Ainslie ; K.J. Beales ; D.M. Cooper ; C.R. Day ; J.D. Rush
- Source: Electronics Letters, Volume 18, Issue 19, p. 842 –844
- DOI: 10.1049/el:19820573
- Type: Article
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Triangular-profile monomode fibre having minimum dispersion at 1.55 μm has been made with an attenuation of 0.24 dB/km at this wavelength. This has better optical performance than fibres optimised for 1.3 μm operation which have typically 1.5 to 2 times this loss at their wavelength of minimum dispersion. The spot sizes of the two fibre types are similar at their respective optimum wavelengths.
Rapid method of determination of carrier mobility against temperature in GaAs MESFETs
- Author(s): B. Kim and B. Das
- Source: Electronics Letters, Volume 18, Issue 19, p. 844 –845
- DOI: 10.1049/el:19820574
- Type: Article
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A simple method of measurement for the determination of μ against T at fixed depths in GaAs MESFET ion-implanted layers has been devised. Typical results showing μ against T at different depths are presented that indicate the relative effects of both the shallow and compensating deep levels near the surface and deep in the channel.
Ultra-low threshold, graded-index waveguide, separate confinement, CW buried-heterostructure lasers
- Author(s): W.T. Tsang ; R.A. Logan ; J.A. Ditzenberger
- Source: Electronics Letters, Volume 18, Issue 19, p. 845 –847
- DOI: 10.1049/el:19820575
- Type: Article
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Ultra-low-threshold semiconductor diode lasers were fabricated by forming buried heterostructures from MBE-grown graded-index waveguide, separate-confinement heterostructure (GRIN-SCH) wafers. CW threshold currents as low as 2.5 mA for 250 μm cavity length, output power as high as 20 mW/mirror and external quantum efficiency as high as 80% were obtained.
Radiation loss in open-waveguide directional couplers
- Author(s): T. Corzani ; L. Manià ; G. Falciasecca
- Source: Electronics Letters, Volume 18, Issue 19, p. 847 –848
- DOI: 10.1049/el:19820576
- Type: Article
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An interesting phenomenon which can occur in open-waveguide directional couplers is discussed. The phenomenon consists of the appearance of radiation, which can considerably modify the behaviour of the coupler. This fact is illustrated by means of analytical and numerical examples.
Power spectra of digital FM signals with complex signalling pulse shapes
- Author(s): K.M. Sundara Murthy and K.W. Cattermole
- Source: Electronics Letters, Volume 18, Issue 19, p. 848 –850
- DOI: 10.1049/el:19820577
- Type: Article
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A method to evaluate the power spectral density (PSD) of digital frequency modulation (DFM) signals with full and partial response signalling pulses of arbitrary shape is given. For rectangular pulse shapes the PSD computation is exact and for other complex pulse shapes the PSD can be computed to any desired accuracy. Previously published results for partial-response signals can be deduced as special cases.
Optical Y-junctions and S-bends formed by preferentially etched single-mode rib waveguides in InP
- Author(s): P. Buchmann and A.J.N. Houghton
- Source: Electronics Letters, Volume 18, Issue 19, p. 850 –852
- DOI: 10.1049/el:19820578
- Type: Article
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Single-mode optical Y-junctions are demonstrated in epitaxial n−/n+ InP. The rib waveguides with rectangular cross-section have been made using wet chemical etching in an HCI:H3PO4 preferential etchant. The minimum measured loss due to the branching point is approximately 1 dB for Y-junctions with a branching angle of 0.9° at the tip.
Digital filters with fast coefficient implementation
- Author(s): J.J. Narraway and R. Venkatesan
- Source: Electronics Letters, Volume 18, Issue 19, p. 852 –853
- DOI: 10.1049/el:19820579
- Type: Article
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A collection of lowpass digital-filter transfer functions is given, each of which has coefficients allowing use of a simple and very fast multiplication scheme.
Semicylindrical Zn-diffused stripe GaAlAs laser diodes with very low threshold currents
- Author(s): K. Hanamitsu ; S. Ohsaka ; K. Yoshida ; H. Nishi ; K. Hori ; M. Takusagawa
- Source: Electronics Letters, Volume 18, Issue 19, p. 853 –855
- DOI: 10.1049/el:19820580
- Type: Article
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Semicylindrical Zn-diffused stripe (SCD) GaAlAs lasers with a very narrow current-confining stripe and sufficient refractive-index step along the active layer are described. They have the lowest threshold current among this type of device previously reported. The devices having a 200 μm cavity length showed a CW threshold current of only 22 mA at 25°C and 45 mA at 105°C. Sufficient current confinement made it possible to operate at temperatures up to 165°C.
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