U
SER
M
ANUAL
750000992/16
1-5
MTS
e
WDM principle and analysis
With this new technology, new measurements are required. During installation
and maintenance of WDM systems, it is important to verify the following
parameters:
1.
Presence of all channels at corresponding wavelengths, without any drift.
2.
Right channel power levels, without any power variation
3.
Enough signal over noise ratio (SNR). This value is determined by measuring
the ratio of the peak channel power to the noise power level of the ASE
1
noise
signals to the left and/or right of the carrier. Usually, the noise measurement
point is chosen as the calculated mid-point between two adjacent channels.
The measured noise power level is converted to a standardized bandwidth of
0.1 nm.
The most important test equipment for WDM systems able to perform those test
is the spectrum analyser. This analyser can be connected along the WDM system
on all critical measurement points, located at the extremities of the links or at the
amplifier locations.
Measurement results
The optical spectrum analyser displays a waveform which is showing all the
channels. Measured results are presented on a complete spectral analysis and as
a WDM table, listing all carriers with their relevant parameters.
The optical spectrum analyser is performing automatic detection and
measurement for all channels.
The number and the composite power are provided like, for each channel:
•
the wavelength
•
the spacing
•
the power level
•
the signal over noise ratio
The total power of the system could also be provided.
In order to qualify the amplifier, tilt and slope gain could be calculated. In
principle, the amplification shall be flat over the full WDM spectrum.
1. Amplified Spontaneous Emission
Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com