Theories, Modelling and Measurement of Noise in
Communication Engineering
By
S M Vaezi-Nejad
Faculty of Computing
London Metropolitan University
London UK
There are three basic elements associated with any communication systems, namely transmitter, transmission
media and the receiver. All these in term may have active and passive components and/or devices which can
contribute to the overall noise generated by any communication systems.
The purpose of this lecture is to outline three aspects of noise in a communication systems; firstly to outline
theories involved when considering the impact of noise in such systems, secondly the most common models
used for analysing noise and thirdly to describe the state of art noise measurement techniques.
The lectures commences with the definition and impact of different types of noise and theories used in
describing thermal noise voltage, shot noise power, noise factor, effective input noise power, relative
intensity and frequency chirp [1, 2].
Modelling of the noise include equivalent voltage and current generators of a noisy resistor, matched load
noise power, total noise power of a system, overall noise figure or equivalent noise temperature of a system
made up of a number of sub-systems, Relative Intensity and frequency chirp noise [ 3,4].
Finally, common noise measurement techniques, novel test equipment and recent advances in measuring
noise are described in some detail [3, 5 ]. In the course of the lecture, references will be made to the outcome
of one of the author’s recent PhD research projects which investigated novel measurement of relative
intensity noise and frequency chirp in DFB lasers used as transmitters in optical networks [3, 6].
References
1- See chapter 7 of the on line book entitled “A new Kind of Science” by Stephen Wolfram’ 2010
http://www.wolframscience.com/nksonline
2- Samrodintsky G and Taqqu M S , Editors “Stable Non-Guassian Random Processes” published by
Chapman & Hall, New York 1994
3- Cox M, “Investigation and development of a novel metrology standard for measurement of relative
intensity noise and frequency chirp of DFB lasers in optical networks”, PhD thesis, Communications
Technology Group, Faculty of Computing, London Metropolitan University May 2007
4- Caroll J, Whiteaway J and Plumb D, “Distributed feedback semiconductor lasers”, Pub by the Institution
of Electrical Engineers, London, UK, 1998 (ISBN 0819426601)
5- Vaezi-Nejad S M, Cox M and Cooper N, “Novel Frequency Chirp Measurement Techniques”
To appear in the Measurement Journal of the Institute of Measurement and Control, Feb/March 2011
6 - Vaezi-Nejad S M, Cox M and Cooper N, “Novel Instrumentation for measurement of Relative Intensity
Noise” To appear in the Transactions of the Institute of Measurement and Control, 2011