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<h1><b><font size=3 face="Times New Roman"><span style='font-size:12.0pt;
font-weight:normal'>ALMA Memo # 506<o:p></o:p></span></font></b></h1>
<h2><b><font size=3 face="Times New Roman"><span style='font-size:12.0pt;
font-weight:normal'>PMD Effects on the Analogue Signal Transmission <br>
<br>
P. Shen, N. J. Gomes, P. A. Davies (UKent), W. P. Shillue (NRAO), P. G. Huggard
(RAL) <br>
<br>
2004-10-08<o:p></o:p></span></font></b></h2>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Keywords: PMD, Polarisation, phase drift, Photonic LO <o:p></o:p></span></font></p>
<p><font size=3 face="Times New Roman"><span style='font-size:12.0pt'>We
address the effects and problems of the polarisation mode dispersion (PMD) in
the fibre transmission system for the Photonic LO. PMD is a random phenomenon,
and varies from fibre to fibre, time to time and wavelength to wavelength.
First, its value directly affects the efficiency of the LO generation. Then,
the long term and short term stability of the PMD affect the long and short
term phase stability of the delivered LO signal. It is suggested that ultra low
PMD fibre should be used to preserve LO generation efficiency, to minimize
system outage, and also maintain better phase stability (less phase drift).
Measures to minimize the PMD effects are suggested. The polarisation mode noise
at the receiver is also discussed. Any components in the receiver with large PMD,
such as optical isolator, amplifier and photodetector will result in observable
polarisation mode noise in the presence of large input polarisation
fluctuation. A major contributor to this fluctuation is the antenna wrap, which
has to be designed with care. <o:p></o:p></span></font></p>
<p style='margin:0in;margin-bottom:.0001pt'><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'>View a pdf version of ALMA Memo #506. <o:p></o:p></span></font></p>
<p class=MsoNormal><u><font size=2 color=blue face="Courier New"><span
style='font-size:10.0pt;font-family:"Courier New";color:blue'><a
href="http://www.alma.nrao.edu/memos/html-memos/alma506/memo506.pdf">http://www.alma.nrao.edu/memos/html-memos/alma506/memo506.pdf</a></span></font></u><o:p></o:p></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
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