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Experts
in Next Generation Lightwave Test Equipment |
40Gb/s QPSK modulation measured
with the AP2440A!
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Optical
Complex Spectrum Analyzer AP2440A application note |
| Introduction
:
Improvement in spectral efficiency
of the WDM system is considered the economical way to enlarge the transmission
capacity. Among several modulation formats, quadrature phase-shift keying
(QPSK) is becoming an attractive candidate during last few years because
it doubles the spectral efficiency of binary PSK (BPSK or DPSK). But,
there was a lack of measurement solutions to visualize the phase modulation
as a function of time, as an oscilloscope does for intensity modulations.
These measurements are now possible with the OCSA AP2440A series.
Below a typical measurement example of a 40Gb/s QPSK modulated signal
is shown.
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40Gb/s QPSK modulation
The 1-2-3-4 markers on the red trace represent the 4
different phase states of the QPSK modulated signal
(left Y-scale = power in mW, right Y-scale is phase in degree)
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| Constellation
display :
A practical way to display intensity and phase modulated
signals is by means of a constellation display. In this graph, the X
scale is the real axis and the Y scale is the imaginary axis. The quality
of the signal can easily be evaluated in this way, as the objective is
to have a box shaped figure with 90 degree corners.
This constellation display feature will be available
for every Apex Technologies OCSA as of January 2006.
Current OCSA users will automatically receive an upgrade notification.
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Click to receive the latest Apex Technologies OCSA application
note:
" New
modulation formats analysis with the AP2440A series
Optical Complex Spectrum Analyzer"
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here to download product brochures
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Request for demonstration or evaluation :
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Visit our web site : www.apex-t.com
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APEX Technologies - 7, rue
Soddy, 94000 Creteil, FRANCE
Tel : +33 1 49 56 99 55 - Fax : +33 1 49 56 91 62
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APEX Technologies
USA- 501-I South Reino Road #332
Newbury Park CA 91320 USA
Tel :
(805)277-0628 - Fax : (805)277-0632
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