Chapter 5 Measurement Functions
5-66
Spectrum Division Calculation Method
The level of the ASE output from the optical amplifier is the sum of the
following levels:
●
Noise Level generated in optical amplifier
●
Noise level for amplified optical signal
The spectrum division method finds the noise level generated in the
optical amplifier (spectrum correction value) by subtracting the amplified
optical signal level from the optical amplifier output level.
The ASE optical output level Pase is measured from the spectrum
correction value, which is calculated using the spectral division method.
The formula for the spectrum correction value Pcorr (λ) is as follows.
The spectrum correction value is calculated after first calculating the
provisional gain G
1
.
BPFLcal
PinlossPin
G
Poutloss
PoutPcorr
⋅
⋅
−
⋅=
)
(
)(
)(
1
l
ll
PinlossPin
PoutlossPout
G
s
s
⋅
⋅
=
)(
)(
1
l
l
Pcorr(λ)
=0 when
Pcorr(λ)
<0
Pin(λ):
Level at optical input wavelength λ (W)
Pout(λ):
Level at optical output wavelength λ (W)
Pinloss:
Linear value for Pin Loss entry
Poutloss:
Linear value for Pout Loss entry
G
1
:
Gain
BPFLcal:
Linear value set at O.BPF Lvl Cal
Calculation using polarization nulling method
The polarization nulling method removes the optical signal from the
optical output using a detector. Consequently, it is not necessary to
subtract the optical signal level from the ASE optical output level.
However, correction is required because the ASE optical output level is
halved by the detector.
In the polarization nulling method, Pin, Pout, and Pase are obtained from
the following equation using the gain and noise figure calculation.
Pase = 2•Psp-ase•Polloss
Pin(λ) = Psp-in(λ)•Pinloss
Pout(λ) = Pap-out(λ)•Poutloss
Psp-ase: ASE level (W) calculated by fitting curve
Polloss: Linear value of value input at Pol Loss
Psp-in(λ): Level at optical input wavelength λ (W)
Pap-out(λ):Level at optical output wavelength λ (W)
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