EXFO FTB -5240S/5240BP Optical Spectrum Analyzer - Manual (Page 627)

Formulas Used with Your Optical Spectrum Analyzer
OSA 621
Bandwidth Calculation (Spectral Transmittance)
Bandwidth Calculation (Spectral
Transmittance)
Bandwidth is calculated using the following equation:
Where
b is the bandwidth at X dB,

N
is the nominal wavelength,

XdBLeft
is the wavelength on the left at which the power is X dB below
the power at the nominal wavelength.

XdbRight
is the wavelength on the right at which the power is X dB
below the power at the nominal wavelength.
b 2Min 
N

XdBLeft
–   
XdBRight

N
–      =