Chapter 5 Measurement Functions
5-48
Spect Div On:
Uses the spectrum division method.
Pout and Pase are obtained by subtracting the level of the optical input
spectrum from the level of the measured output spectrum.
PLZN Nulling:
Polarization Nulling Method
With the polarization nulling method, Pout and Pase are obtained by
assuming that the state of polarization of the optical output from the
optical amplifier is as follows:
•
The signal is polarized.
•
The ASE is unpolarized.
If the signal is blocked by the polarizer, then the ASE level can be
measured. Pout is the level when the optical signal is passed by the
polarizer and Pase is the level when it is blocked by the polarizer.
Pulse Method:
Pulse Method
The ASE level of the optical amplifier is the level that is held for an
instant after the optical signal level is blocked. The pulse modulated
optical signal is input to the optical amplifier and Pout and Pase are
measured by making use of this property.
Pout is the output level when the optical signal is on and Pase is the
output level when the optical signal is off.
WDM Measure:
Measurement of wavelength multiplexed light
The gain and noise figure are measured for the wavelength
multiplexed light. Pout and Pase are measured using the pulse method
described above for the target wavelength.
●
ASE Fitting
At Spect Div Off and Spect Div On, Pase is obtained from the spectrum
through an approximation method by a fitting method.
There are two types of fitting method as follows:
Gauss Fitting:
Fitting Method Using a Gaussian Function
Fitting is performed using the second-order approximation
L(λ)=aλ
2
+bλ+c from data in the range of λ1 to λ2 (dBm units) and λ3 to
λ4 in Figure 5.7.1-2 (a). The level of the optical signal wavelength λs
found from this function is Pase.
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