In conclusion, an optical power meter is designed to measure the power of optical signals at specific wavelengths, primarily 850 nm for short-distance applications and 1300-1310 nm for medium-distance applications. What people often refer to as wavelength range describes the span where an optical power meter works best. Getting this right matters a lot because if the meter isn't calibrated for the right range, its readings won't be accurate or reliable. For light power measurements outside the field of. While optical power meters are the primary power measurement instrument, optical loss test sets (OLTSs) and optical time domain reflectometers (OTDRs) also measure power in testing loss.