Online ISSN
1350-911X
Print ISSN
0013-5194
Electronics Letters
Volume 19, Issue 11, 26 May 1983
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Volume 19, Issue 11
26 May 1983
Novel polarisation phenomena on anisotropic multimoded fibres
- Author(s): A.W. Snyder and F. Rühl
- Source: Electronics Letters, Volume 19, Issue 11, p. 401 –402
- DOI: 10.1049/el:19830275
- Type: Article
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p.
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–402
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The lowest-order modes of multimoded fibres composed of birefringent material can differ radically from the familiar modes of multimoded isotropic fibres. In general, the modal fields are neither uniformly polarised nor circularly symmetric as they would be on circularly symmetric isotropic fibres that are weakly guiding. Thus multimoded anisotropic fibres can exhibit dramatic polarisation effects which may have important practical applications.
LPE growth of InP/InGaAs/InP DH wafers on (100) InP substrates
- Author(s): N.S. Takahashi ; T. Sasaki ; A. Fukushima ; S. Kurita
- Source: Electronics Letters, Volume 19, Issue 11, p. 402 –403
- DOI: 10.1049/el:19830276
- Type: Article
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–403
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An InP/InGaAs/InP double heterostructure wafer is grown directly on a (100) InP substrate using very low temperature LPE growth. This crystal exhibits a thin transition layer at a InP-InGaAs interface because of dissolution of the ternary layer.
Velocity measurement of multiple leaky waves on germanium by line-focus-beam acoustic microscope using FFT
- Author(s): J. Kushibiki ; K. Horii ; N. Chubachi
- Source: Electronics Letters, Volume 19, Issue 11, p. 404 –405
- DOI: 10.1049/el:19830277
- Type: Article
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p.
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–405
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V(z) curves obtained by the acoustic line-focus beam are deformed due to multiple leaky waves. A novel velocity measurement method with FFT is developed for a V(z) curve analysis. Experiments are performed for a (111)-Ge sample and two mode spectra are separately measured corresponding to two velocities for a leaky SAW and a leaky pseudo-SAW existing on the boundary of water/sample.
Error rates for M-ary noncoherent FSK in impulsive reverberation noise
- Author(s): A.M. Maras ; H. Davidson ; A.G.J. Holt
- Source: Electronics Letters, Volume 19, Issue 11, p. 405 –406
- DOI: 10.1049/el:19830278
- Type: Article
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–406
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It is shown that reverberation noise for primary acoustic scattering in the ocean has an integral representation and that a canonical model for its analysis can be found. Exact values of error rates for M-ary noncoherent FSK for correlation receivers in such noise are given. Comparison with the well known Gaussian case is also made.
Degradation mechanism in 1.3 μm InGaAsP/InP buried crescent laser diode at a high temperature
- Author(s): E. Oomura ; H. Higuchi ; R. Hirano ; Y. Sakakibara ; H. Namizaki ; W. Susaki
- Source: Electronics Letters, Volume 19, Issue 11, p. 407 –408
- DOI: 10.1049/el:19830279
- Type: Article
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–408
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A leakage current flowing through a junction between a p-InP current blocking layer and an n-InP cladding layer is examined in connection with a degradation of a buried crescent laser diode at a high temperature. The degradation characteristics have been successfully explained by a theoretical model proposed in this study.
Helium speech processor using linear prediction
- Author(s): S.W. Beet and C.C. Goodyear
- Source: Electronics Letters, Volume 19, Issue 11, p. 408 –410
- DOI: 10.1049/el:19830280
- Type: Article
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–410
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Currently available helium speech processors provide a linear frequency scaling but, at the greater depths encountered in recent years, a nonlinear shift is desirable. Here, we suggest a method based on linear prediction, which will produce such a shift, while retaining a reasonably low computational cost.
Bipolar transistor with graded band-gap base
- Author(s): J.R. Hayes ; F. Capasso ; A.C. Gossard ; R.J. Malik ; W. Wiegmann
- Source: Electronics Letters, Volume 19, Issue 11, p. 410 –411
- DOI: 10.1049/el:19830281
- Type: Article
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–411
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We report the first compositionally graded base bipolar transistor. The device grown by MBE incorporates a wide gap Al0.35Ga0.65As emitter (n = 2 × 1016/cm3 and a 0.4 μm thick p+ (= 2 × 1018/cm3)base graded from Al0.20Ga0.80As to GaAs. DC current gain of 35 with flat, nearly ideal, collector characteristics are observed. Incorporation of a graded gap base gives much faster base transit times due to the induced quasi-electric field for electrons, thus allowing a precious tradeoff against the base resistance.
Residual nylon-jacketed-fibre shrinkage caused by cooling
- Author(s): N. Yoshizawa ; T. Yabuta ; K. Noguchi
- Source: Electronics Letters, Volume 19, Issue 11, p. 411 –412
- DOI: 10.1049/el:19830282
- Type: Article
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p.
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–412
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Excess shrinkage of nylon-jacketed optical fibres after heating is observed, and it is shown that this shrinkage induces an optical-loss change of the jacketed fibre.
Coding technique for progressive transmission of static images
- Author(s): R.A. Packwood and G.R. Martin
- Source: Electronics Letters, Volume 19, Issue 11, p. 412 –413
- DOI: 10.1049/el:19830283
- Type: Article
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–413
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A new technique for computing invertable approximate averages for image transmission is described. It has been shown that an image transmitted by block averages can be subjectively improved without transmission overhead and in real time.
Efficient SAW convolver with 30 μs integration time
- Author(s): M.F. Lewis and C.L. West
- Source: Electronics Letters, Volume 19, Issue 11, p. 413 –415
- DOI: 10.1049/el:19830284
- Type: Article
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p.
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–415
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A SAW convolver is described with input bandwidth 20 MHz and integration time in excess of 30 μs. It displays a high convolution efficiency (≃ −63 dBm) and self convolution suppression exceeding 40 dB.
1.5 μm wavelength GaInAsP C3 lasers: single-frequency operation and wideband frequency tuning
- Author(s): W.T. Tsang ; N.A. Olsson ; R.A. Linke ; R.A. Logan
- Source: Electronics Letters, Volume 19, Issue 11, p. 415 –417
- DOI: 10.1049/el:19830285
- Type: Article
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p.
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–417
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We have characterised the temporal-spectral behavior of 1.5 μm wavelength cleaved-coupled-cavity (C3) lasers. Single longitudinal mode discrimination ratios in excess of 500:1 have been obtained under high bit rate modulation. Bit error rate of less than ≲ 10−9 were obtained under single-frequency operation with direct modulation up to 1 Gbit/s. Averaged frequency tuning rates as large as 26 Å/mA and frequency tuning excursion of 300 Å were achieved when the C3 laser was operated in a frequency modulation mode.
Bit-error rate of PSK heterodyne optical communication system and its degradation due to spectral spread of transmitter and local oscillator
- Author(s): K. Kikuchi ; T. Okoshi ; M. Nagamatsu ; N. Henmi
- Source: Electronics Letters, Volume 19, Issue 11, p. 417 –418
- DOI: 10.1049/el:19830286
- Type: Article
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p.
417
–418
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In a PSK heterodyne optical communication system, the FM noise of the transmitter and local oscillator degrades the bit-error rate (BER). A theory is presented giving the BER of such a system considering the FM-noise effect. To verify the theory, BER measurement is performed using a simulation model of the PSK heterodyne system.
Au-Mg improved ohmic contacts to p-GaAs
- Author(s): N.A. Papanicolaou and A. Christou
- Source: Electronics Letters, Volume 19, Issue 11, p. 418 –420
- DOI: 10.1049/el:19830287
- Type: Article
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–420
(3)
A novel ohmic contact alloy to p-GaAs consisting of 96 weight % Au and 4 weight % Mg, a Mo barrier metal and Au overlay is described. Contact resistivities as low as 8 × 10−5 cm2 were achieved on heavily doped substrates. Auger sputter profiles have shown these contacts to be thermally stable up to 450°C.
Noise reduction in ADPCM AQJ systems using quantiser correction at the receiver
- Author(s): F.S. Yeoh and C.S. Xydeas
- Source: Electronics Letters, Volume 19, Issue 11, p. 420 –421
- DOI: 10.1049/el:19830288
- Type: Article
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p.
420
–421
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A technique is considered which reduces the output noise in ADPCM-AQJ speech coders. Computer simulation results indicate a subjectively perceptible enhancement in the quality of the recovered speech.
Calculating transfer function and its first- and second-order sensitivities using one network analysis
- Author(s): P.H. di Mambro
- Source: Electronics Letters, Volume 19, Issue 11, p. 421 –423
- DOI: 10.1049/el:19830289
- Type: Article
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–423
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The method calculates the transfer function and its sensitivities at a single frequency for both passive and active networks including constant delays. As the method requires only a single network analysis it is particularly useful for large networks. Although it uses nodal admittance representation it can be extended to other methods of network analysis.
New approach to the manufacture of low-threshold 1.5 μm distributed feedback lasers
- Author(s): L.D. Westbrook ; A.W. Nelson ; C. Dix
- Source: Electronics Letters, Volume 19, Issue 11, p. 423 –424
- DOI: 10.1049/el:19830290
- Type: Article
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p.
423
–424
(2)
Low-threshold-current (85 mA), oxide isolated InGaAsP/InP distributed feedback (DFB) lasers operating at a wavelength of λ = 1.5 μm have been produced for the first time using electron-beam-written DFB corrugations overgrown by MOCVD. The control and flexibility afforded by these techniques considerably ease the complexity of DFB laser manufacture.
Balanced minimal realisation of SISO systems
- Author(s): C.P. Therapos
- Source: Electronics Letters, Volume 19, Issue 11, p. 424 –426
- DOI: 10.1049/el:19830291
- Type: Article
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p.
424
–426
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A method is proposed for the derivation of an internally balanced minimal-state-space description of a SISO system, given its transfer function. The method requires only once the computation of the eigenvalues-eigenvectors of a symmetric matrix. Solution of the Lyapunov matrix equation is not needed.
Improved Padé approximants using stability equation method
- Author(s): J. Pal
- Source: Electronics Letters, Volume 19, Issue 11, p. 426 –427
- DOI: 10.1049/el:19830292
- Type: Article
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426
–427
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The stability equation method for obtaining reduced order Padé models may approximate the nondominant poles of the system, thus giving bad approximations. A modified method is given that overcomes the above drawback.
Modes of operation in dual-gate MESFET mixers
- Author(s): H. Ashoka and R.S. Tucker
- Source: Electronics Letters, Volume 19, Issue 11, p. 428 –429
- DOI: 10.1049/el:19830293
- Type: Article
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p.
428
–429
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The mechanisms of mixing in a dual-gate GaAs MESFET mixer are described. Based on a cascode DC model of the device, several modes of mixer operation are identified. It is shown that each single-gate MESFET in the cascode model can operate as a mixer or amplifier, depending on the DC bias conditions and mixer configuration.
Bandwidth limits of nonlinear (soliton) optical communication systems
- Author(s): K.J. Blow and N.J. Doran
- Source: Electronics Letters, Volume 19, Issue 11, p. 429 –430
- DOI: 10.1049/el:19830294
- Type: Article
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–430
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We have shown that interactions between pulses can lead to a significant reduction of the bandwidth of nonlinear systems. The inclusion of loss is essential and implies that solitons must be launched with a separation of at least 10 times their pulse width for short systems of ∼ 30 km and even more for longer systems.
Multiquartic approximation in single-mode optical fibres
- Author(s): G. Coppa and P. di Vita
- Source: Electronics Letters, Volume 19, Issue 11, p. 430 –432
- DOI: 10.1049/el:19830295
- Type: Article
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p.
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–432
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A new stratification method based on the approximation of the actual index profile of the fibre by means of a set of quartic curves is proposed. The method permits one to deduce accurately the propagation characteristics in the least calculation time, particularly on fibres with nonmonotonic index profiles.
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