Agilent Technologies Agilent 86120C manual Σ Pi

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.
			N				λi
	MeanWavelength =		Σ		Pi
							P°
			i = 1
	where, Po 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.
		N	(λi –			)2
	σ =			λ
		Σ Pi	-------------------- 
		i = 1	Po

where:

λis the mean wavelength as defined above.

Pi is the power of a single peak.

Po is total power as defined in this section.

2-32