I want to check reflectivity of a mirror using OSA and then plot the graph of reflectivity (%) vs wavelength(nm). Can I do it using OSA or I have to calculate reflectivity from the output power obtained form OSA? I use circulator with insertion loss around 0.41dB from port 1 to 2 and 0.39 from port 2 to 3. Do I have to consider these values when calculating reflectivity?