D.W. Smith
BT Group
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Featured researches published by D.W. Smith.
Archive | 1983
D.W. Smith; R.A. Harmon; T.G. Hodgkinson
Heterodyne (1) and homodyne (2) detection schemes are presently being developed as an alternative to direct detection in optical fibre communications. These coherent systems can offer better receiver sensitivity and will allow the available bandwidth of monomode fibre to be used efficiently. However, their performance will be dependent on matching the polarisation state (S.O.P) at the output of the transmission fibre to that of the local oscillator, as Fig 1 illustrates. This paper discusses techniques that can be used by the system designer to overcome the problems of polarisation matching, and it presents experimental results obtained from a coherent transmission system operating over conventional circular core fibre.
Annales Des Télécommunications | 1983
T.G. Hodgkinson; R. Wyatt; D. J. Malyon; B. K. Nayar; R. A. Harmon; D.W. Smith
The authors consider the design requirements for 1.52 μm coherent optical fibre transmission systems. Some of the essential requirements are: narrow linewidth sources, polarisation stable transmission media, low insertion loss optical mixers and frequency tracking or phase locked local oscillators. Having been successful in reducing the linewidth of semiconductor lasers to less than 30 kHz, by using injection locking techniques, and in fabricating optical mixers with insertion losses of the order of dB, they have been able to experiment with coherent optical fibre transmission systems to assess their practicability. In this paper it will be shown that coherent systems can be operated over long lengths of conventional low loss monomode fibre without any polarisation penalty and give far better performance than direct detection systems.AnalyseLes auteurs étudient la conception de systèmes caractérisés par des services à largeur de raie étroite (moins de 30 kHz), un milieu de transmission stable en polarisation, des mélangeurs optiques à faible affaiblissement d’insertion (moins de 1 dB), des oscillateurs locaux à poursuite de fréquence ou à verrouillage de phase.
Electronics Letters | 1987
T.G. Hodgkinson; R.A. Harmon; D.W. Smith
Electronics Letters | 1986
C.G. Atkins; D. Cotter; D.W. Smith; R. Wyatt
Electronics Letters | 1985
T.G. Hodgkinson; R.A. Harmon; D.W. Smith
Electronics Letters | 1986
D.J. Malyon; D.W. Smith; R. Wyatt
Electronics Letters | 1983
R. Wyatt; T.G. Hodgkinson; D.W. Smith
Electronics Letters | 1983
D.J. Malyon; T.G. Hodgkinson; D.W. Smith; R.C. Booth; B.E. Daymond-John
Electronics Letters | 1984
R. Wyatt; D.W. Smith; T.G. Hodgkinson; R.A. Harmon; W.J. Devlin
Electronics Letters | 1982
R. Wyatt; D.W. Smith; K.H. Cameron
