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Making Measurements
Measuring Fabry-Perot (FP) Lasers
Measurement Description
FWHM FWHM (full width at half maximum) describes the spectral
width of the half-power points of the laser, assuming a
continuous, Gaussian power distribution. The half-power points
are those where the power spectral density is one-half that of
the peak amplitude of the computed Gaussian curve.
FWHM = 2.355 σ
where, σ is sigma as defined below.
MEAN The wavelength representing the center of mass of selected
peaks. The power and wavelength of each spectral component
are used to calculate the mean wavelength.
where, P
o
is total power as defined in this section.
MODE The mean wavelength spacing between the individual spectral
components of the laser.
PEAK The power level of the peak spectral component of the laser.
The wavelength of the peak spectral component.
SIGMA An rms calculation of the spectral width of the laser based on a
Gaussian distribution. The power and wavelength of each
spectral component is used to calculate mean wavelength.
where:
λ
is the mean wavelength as defined above.
P
i
is the power of a single peak.
P
o
is total power as defined in this section.
MeanWavelength
N
Σ
i1=
= P
i
λ
i
P
°
σ
N
Σ
i1=
P
i
λ
i
λ–()
2
P
o
------- --------------
=