The APEX Technologies Optical Spectrum Analyzers clearly show much more details than the grating based OSA and leaves any kind of guess work behind.
Use it as a Wavelength Meter…
The 3 internal Wavelength calibrators (absolute and relative) allow the equipment to provide an excellent wavelength accuracy specification (+/- 3 pm). This high wavelength accuracy gives the possibility to use the equipment as a wavelength meter.
Optical spectrum analyzer with an High Wavelength Accuracy