The maximum input power that the AQ6370B can measure for pulsed light measurements is +20dBm per resolution at full span, per channel. Keep in mind that this limit is applicable to an averaged power of pulsed light, not to the pulse peak power. You will need to calculate an average power with pulse width, pulse peak power, and pulse repetition rate.
High performance with a 20 picometer wavelength resolution supporting 25 GHz DWDM spacing and 40G/100G applications, this OSA also supports non-Telecom applications with a wavelength range from 600nm to 1700nm.
An Optical Spectrum Analyzer (or OSA) is a precision instrument designed to measure and display the distribution of power of an optical source over a specified wavelength span. An OSA trace displays power in the vertical scale and the wavelength in the horizontal scale.
Optical test equipment or optical measuring instruments are used to measure and characterize the physical properties of light.