Optical Spectrum analyzers (OSA) are instruments that measure the Optical Power as a function of Wavelength or frequency.

A spectrometer spectrally divides the Light under measurement by transmitting the components thereof at different, wavelength-by-wavelength angles using a Chromatic Dispersion device, and detects the light thus spectrally divided by the chromatic Dispersion device, using an optical detector. Optical spectrum analyzers are used for analyzing the output light beams from lasers, light-emitting diodes and other light sources. Optical spectrum analyzers are particularly useful for analyzing light sources for optical telecommunications, where it is preferable to ensure that the optical carrier includes only a single, spectrally pure wavelength. The three main optical spectrum resolving technologies that have been used in optical spectrum analyzers are Michelson interferometers, tunable Fabry-Perot optical filters and Diffraction gratings. Optical spectrum analyzers typically comprise a tunable Filter that Bandpass filters an input signal. A Detector is used to measure the filtered signal and thereby determine the optical power within the filter’s current pass band. In optical spectrum analyzers, the light Intensity of a light beam is displayed as a function of wavelength over a predetermined wavelength range. Parameters of importance include wavelength range, wavelength and amplitude accuracy, sensitivity, resolution, measurement speed, Polarization insensitivity and dynamic range.