Online ISSN
1350-911X
Print ISSN
0013-5194
Electronics Letters
Volume 17, Issue 15, 23 July 1981
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Volume 17, Issue 15
23 July 1981
Polarisation beat length measurement in a single-mode optical fibre by backward Rayleigh scattering
- Author(s): M. Nakazawa ; T. Horiguchi ; M. Tokuda ; N. Uchida
- Source: Electronics Letters, Volume 17, Issue 15, p. 513 –515
- DOI: 10.1049/el:19810359
- Type: Article
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Polarisation fluctuation on the backward Rayleigh scattered signal measured by the POTDR (polarisation optical time domain reflectometer) has been investigated by means of the power spectrum. As a result, the spectrum is sharply peaked at the Fourier frequency of 8.3 × 106 Hz determined by the polarisation beat length of 12 m due to the difference in phase velocities between the orthogonal eHE11 and oHE11 modes. The value is in good agreement with the analysis.
Achievement of 1 MHz frequency stability of semiconductor lasers by double-loop AFC scheme
- Author(s): K. Kikuchi ; T. Okoshi ; S. Kawanishi
- Source: Electronics Letters, Volume 17, Issue 15, p. 515 –516
- DOI: 10.1049/el:19810360
- Type: Article
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A temperature-controlling AFC system has been developed to realise high-frequency stability with semiconductor lasers. The frequency drift in DC operation can be reduced to below 1 MHz peak-to-peak. When necessary, the laser frequency can be modulated directly in the AFC state while the centre frequency is kept stabilised within 3 MHz. A heterodyne experiment was also performed using two frequency stabilised lasers; a stable IF output could be obtained for 10 min.
Groove-guide microwave detector for 100 GHz operation
- Author(s): D.J. Harris and S. Mak
- Source: Electronics Letters, Volume 17, Issue 15, p. 516 –517
- DOI: 10.1049/el:19810361
- Type: Article
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A detector has been designed and constructed, using a beam-lead diode, directly in a groove guide. A triangular dipole, produced by photolithography on RT/Duroid 5880, is placed transversely across the guide. A GEC beam-lead Schottky diode, bonded across the dipole, acts as the rectifying element. When used with a cylindrical back short-circuit and an appropriate bias current, a voltage sensitivity of about 400 VW−1 and a tangential sensitivity of about −42 dBm was obtained at a frequency of 100 GHz.
Optical transmission of 16 digitised TV channels over 21 km fibre at a bit rate of 1.12 Gbit/s
- Author(s): C. Baack ; G. Elze ; B. Enning ; G. Heydt ; G. Walf ; G. Wenke
- Source: Electronics Letters, Volume 17, Issue 15, p. 517 –519
- DOI: 10.1049/el:19810362
- Type: Article
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The letter describes an optical transmission system which carries 16 digitised TV channels over a distance of 21 km without repeater at a bit rate of 1.12 Gbit/s.
Evaluation of the gallager adaptive convolutional codes on real channels
- Author(s): B. Vučetić
- Source: Electronics Letters, Volume 17, Issue 15, p. 519 –520
- DOI: 10.1049/el:19810363
- Type: Article
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In the letter the performances of Gallager codes, and hybrid systems based on these codes, are evaluated on real channels using the Monte Carlo simulation method. The new criteria are proposed for diffuse bursts as well as for hybrid systems. Test results demonstrate that these codes, if properly used, offer a significant reduction in the error rate.
Linearly focused acoustic beams for acoustic microscopy
- Author(s): J. Kushibiki ; A. Ohkubo ; N. Chubachi
- Source: Electronics Letters, Volume 17, Issue 15, p. 520 –522
- DOI: 10.1049/el:19810364
- Type: Article
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A linearly focused acoustic beam is investigated to be introduced into acoustic microscopy for characterising materials in the nonscanning version. The new acoustic beam enables us to detect acoustic anisotropies of materials to be measured successfully. For forming the acoustic beam, an acoustic sapphire lens with a cylindrical concave surface of 1.0 mm in radius is made and the acoustic field distributions are investigated at 200 MHz.
Analysis for optimum threshold voltage and load current of E-D-type GaAs DCFL circuits
- Author(s): M. Ino ; M. Hirayama ; M. Ohmori
- Source: Electronics Letters, Volume 17, Issue 15, p. 522 –523
- DOI: 10.1049/el:19810365
- Type: Article
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A GaAs MESFET E-D invertor was analysed to estimate the optimum threshold voltage VT for a switching FET, and the optimum load current IL for a load FET, that will minimise the invertor switching time. The calculated results show that the optimum VT lies at around 0.2 V, and the optimum IL is about 55% of the saturation current of the switching FET.
Interferometric current sensors using optical fibres
- Author(s): A. Dandridge ; A.B. Tveten ; T.G. Giallorenzi
- Source: Electronics Letters, Volume 17, Issue 15, p. 523 –525
- DOI: 10.1049/el:19810366
- Type: Article
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Two types of fibre-optic current sensor have been developed and successfully tested in the laboratory: magnetostrictive jacketing materials and a heating effect, to produce a phase shift in the optical fibre. A ruggedised all-fibre interferometer powered by a diode laser was used to detect the phase changes induced by the electrical current.
Modified VAD method for optical-fibre fabrication
- Author(s): K. Imoto and M. Sumi
- Source: Electronics Letters, Volume 17, Issue 15, p. 525 –526
- DOI: 10.1049/el:19810367
- Type: Article
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New techniques for protecting the burner flame and controlling gas pressure in a reaction vessel have been developed for the vapour-phase axial-deposition (VAD) method of soot preform. The growth of soot preform became more stable. It is found that there is a close correlation between the bottom shape of the soot preform and the refractive-index profile of a fibre preform. Optical fibres thus produced indicate improved reproducibility in the bandwidth above 800 MHz km at a wavelength of 0.85 μm.
TSRMA — a communication protocol for data transmission by radio channels
- Author(s): A. Abramovitz and Y. Bar-Ness
- Source: Electronics Letters, Volume 17, Issue 15, p. 526 –527
- DOI: 10.1049/el:19810368
- Type: Article
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The time slot reservation multiple access (TSRMA) protocol proposed here fits today's real environment, is easy to implement, and performs well in terms of channel utilisation and expected packet delay.
High rate pulse generation from InGaAsP laser in selfoc lens external resonator
- Author(s): S. Akiba ; G.E. Williams ; H.A. Haus
- Source: Electronics Letters, Volume 17, Issue 15, p. 527 –529
- DOI: 10.1049/el:19810369
- Type: Article
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High rate modulation of an InGaAsP diode laser at rates of 5–10 GHz was demonstrated using a selfoc microlens external resonator. At a rate of 5.3 GHz modelocked pulses of 30 ps duration were obtained, whereas deeply modulated output was observed at 8.1 and 9.4 GHz rates.
Operational amplifier with compensation pole as basis for active networks
- Author(s): H. Sutcliffe and C.Y. Wong
- Source: Electronics Letters, Volume 17, Issue 15, p. 529 –530
- DOI: 10.1049/el:19810370
- Type: Article
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Controversy concerning the use of the ωT/s idealisation of the characteristics of operational amplifiers is reviewed. Measurements of the variation of ωT with various factors are reported and conclusions are reached relating to the validity of this approach to the engineering design of active networks.
Low-loss single polarisation fibres with asymmetrical strain birefringence
- Author(s): T. Hosaka ; K. Okamoto ; T. Miya ; Y. Sasaki ; T. Edahiro
- Source: Electronics Letters, Volume 17, Issue 15, p. 530 –531
- DOI: 10.1049/el:19810371
- Type: Article
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Low-loss and highly birefringent single polarisation fibres have been fabricated. The minimum transmission loss and the modal birefringence of the fibre with refractive-index difference Δ=0.61% was 0.62 dB/km at λ=1.52 μm and 8.5×10−5 at λ=1.15 μm, respectively. The state of linear polarisation was stable against the handling conditions such as bending, twists, concentrated force, and temperature variations.
Diffusion of transition elements in GaAs and InP
- Author(s): M.R. Brozel ; B. Tuck ; E.J. Foulkes
- Source: Electronics Letters, Volume 17, Issue 15, p. 532 –533
- DOI: 10.1049/el:19810372
- Type: Article
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–533
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A technique is presented for studying the diffusion of iron and chromium in GaAs and InP at temperatures down to 600°C. The technique is reproducible, and results are presented which show that in all four cases very fast diffusion occurs.
New commutated Doppler radar system
- Author(s): F.R. Connor
- Source: Electronics Letters, Volume 17, Issue 15, p. 533 –534
- DOI: 10.1049/el:19810373
- Type: Article
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A new design for a double-sideband commutated Doppler primary radar system for detecting a target is proposed. Target information is obtained by the measurement of various Doppler frequencies, and a unique feature of the system is its combined use of frequency diversity, space diversity and time diversity to achieve a better overall performance.
Anisotropy detection in sapphire by acoustic microscope using line-focus beam
- Author(s): J. Kushibiki ; A. Ohkubo ; N. Chubachi
- Source: Electronics Letters, Volume 17, Issue 15, p. 534 –536
- DOI: 10.1049/el:19810374
- Type: Article
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Nonscanning reflection acoustic microscopes can be satisfactorily applied to detect the anisotropy of acoustic properties of solid materials using a line-focus beam. As a demonstration, the anisotropic dependence of leaky surfac-acoustic-wave velocities on the propagation directions are measured on the water/Z-cut-sapphire boundary at a frequency of 200 MHz. The measured values are in good agreement with the calculated results within a difference of about 1%.
Low-noise two-dimensional electron gas FET
- Author(s): M. Laviron ; D. Delagebeaudeuf ; P. Delescluse ; J. Chaplart ; N.T. Linh
- Source: Electronics Letters, Volume 17, Issue 15, p. 536 –537
- DOI: 10.1049/el:19810375
- Type: Article
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Two-dimensional electron gas FETs (TEGFETs) have been fabricated on an N-AlGaAs-GaAs heterojunction. Microwave results at 10 GHz are: NF=2.3 dB, Gass=10.3 dB and Gmax=13.2 dB. These first results obtained on nonoptimised material and processing suggest that TEGFET can be superior to a conventional GaAs FET.
Offset voltage, CMRR and PSRR of a long-tailed pair: an integrated approach
- Author(s): B.L. Hart
- Source: Electronics Letters, Volume 17, Issue 15, p. 537 –539
- DOI: 10.1049/el:19810376
- Type: Article
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An integrated treatment of the input offset-voltage Vos, common-mode rejection ratio (CMRR) and power supply rejection ratio (PSRR) of a simple resistively loaded bipolar differential amplifier establishes the basic theoretical relationships between these parameters and indicates that ‘Early-voltage’ mismatch of the constituent devices limits the attainable CMRR and PSRR.
Transferred-electron oscillators at very high frequencies
- Author(s): A.M. Mazzone and H.D. Rees
- Source: Electronics Letters, Volume 17, Issue 15, p. 539 –540
- DOI: 10.1049/el:19810377
- Type: Article
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The high-frequency characteristics of transferred-electron oscillators have been examined by computer simulation. Maximum frequencies in the range 100 to 200 GHz (for GaAs) and contact effects favouring current saturating cathodes are predicted.
Alternating beam method (ABM) in photothermal microscopy (PTM) and photoacoustic microscopy (PAM)
- Author(s): A. Lehto ; M. Jokinen ; J. Jaarinen ; T. Tiusanen ; M. Luukkala
- Source: Electronics Letters, Volume 17, Issue 15, p. 540 –541
- DOI: 10.1049/el:19810378
- Type: Article
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In measuring thermal properties of nearly uniform surfaces, it is often difficult to resolve small differences in the surfaces. The letter reports a differential method to measure small variations with the detector operating as a null detector. This method is applied to measure the thickness of plasma-sprayed coatings.
Picosecond pulse generation by lateral mode switching of (GaAl)As-heterostructure stripe lasers
- Author(s): I.H. White ; G.J. Aspin ; J.E. Carroll ; R.G. Plumb
- Source: Electronics Letters, Volume 17, Issue 15, p. 541 –543
- DOI: 10.1049/el:19810379
- Type: Article
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The presence of ‘kinks’ in the light/current characteristics of (GaAl)As injection lasers is investigated by applying large amplitude electrical RF modulation. It is suggested that the 20 ps pulses which have been observed may be produced through mechanisms associated with these kinks.
Reliability of a new method for measurements of modal power distribution in optical fibres with application to mode scrambler testing
- Author(s): M. Calzavara ; P. Di Vita ; U. Rossi
- Source: Electronics Letters, Volume 17, Issue 15, p. 543 –545
- DOI: 10.1049/el:19810380
- Type: Article
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An experimental investigation about the reliability of an attractive method recently proposed for modal power distribution measurements in multimode fibres is performed. The method is shown to work also in some common cases when the hypotheses of validity are not rigorously fulfilled. Finally, an illustrative application to the testing of mode scramblers is presented.
Field dependence of mobility in Al0.2Ga0.8As/GaAs heterojunctions at very low fields
- Author(s): T.J. Drummond ; M. Keever ; W. Kopp ; H. Morkoç ; K. Hess ; B.G. Streetman ; A.Y. Cho
- Source: Electronics Letters, Volume 17, Issue 15, p. 545 –547
- DOI: 10.1049/el:19810381
- Type: Article
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Multiple-period (Al, Ga)As/GaAs modulation doped heterojunction structures have been grown with molecular beam epitaxy. Electron mobilities of about 200 000 cm2/Vs at 10 K and 90000 cm2/Vs at 77 K with associated sheet carrier concentrations of about 2×1012 cm−2 have been observed. The current parallel to the interfaces for low electric fields was examined as a function of lattice temperature. The electron mobility has been observed to be strongly dependent on the strength of the electric field, and hot electron effects were observable at a field as low as 10 V/cm. To our knowledge this is the first report of hot electron phenomena in GaAs at such small fields.
Fast biased polynomial transforms for two-dimensional convolutions
- Author(s): Soo-Chang Pei and Ja-Ling Wu
- Source: Electronics Letters, Volume 17, Issue 15, p. 547 –548
- DOI: 10.1049/el:19810382
- Type: Article
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The fast biased polynomial transforms are defined directly on the ZN−1 ring instead of a conventional cyclotomic polynomial ring. Such biased polynomial transforms may be combined with very efficient fast FFT algorithms. Two-dimensional convolutions may be carried out without using the complicated Chinese remainder theorem, complex mapping and column-row reordering processes.
Retiming 2.24 Gbit/s and demultiplexing 2.24 to 1.12 Gbit/s in an optical transmission system by means of a single-gate field-effect transistor
- Author(s): B. Enning
- Source: Electronics Letters, Volume 17, Issue 15, p. 548 –549
- DOI: 10.1049/el:19810383
- Type: Article
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In the letter a circuit is presented which can be used for retiming and demultiplexing in Gbit/s applications. Taking advantage of the three-port properties of a field-effect transistor only one transistor is needed.
Comment: Lossless inductor simulation: novel configurations using DVCCS
- Author(s): V.K. Singh
- Source: Electronics Letters, Volume 17, Issue 15, p. 549 –550
- DOI: 10.1049/el:19810384
- Type: Article
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Reply: Lossless inductor simulation: novel configurations using DVCCS
- Author(s): R. Nandi
- Source: Electronics Letters, Volume 17, Issue 15, p. 550 –551
- DOI: 10.1049/el:19810385
- Type: Article
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Analysis of multimode optical fibres with profile perturbations
- Author(s): A. Ankiewicz and C. Pask
- Source: Electronics Letters, Volume 17, Issue 15, p. 551 –552
- DOI: 10.1049/el:19810386
- Type: Article
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A new method for calculating transit times in fibres with perturbed profiles is presented. The effects of perturbations and their variations along the fibre are displayed explicitly in a formula which is mathematically simple and which can be used analytically in many cases of practical interest.
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