Patent ID: 8264682

Claim:
An optical spectrum analyzer for generating dispersed light beams having particular wavelengths from incident light, and measuring an optical spectrum of the incident light by measuring intensities of the dispersed light beams, the optical spectrum analyzer comprising: a diffraction grating to extract and output a component light of a particular wavelength; a diffraction grating controller to change the wavelength of the component light by driving the diffraction grating to change the relative angle with the incident light; a light detector to detect light intensity of the component light; a calculator configured to calculate a target diffraction grating angle data where a wavelength component extracted by the diffraction grating becomes a sampling wavelength of the component light to detect intensity, and to store the calculated target diffraction grating angle data in an inner memory; and a FIFO memory to receive a part of the target diffraction grating angle data stored in the inner memory, and output the target diffraction grating angle data each time a trigger signal indicating timing of sampling is generated, a trigger signal generator configured to generate the trigger signal based on the target diffraction grating angle data output by the FIFO memory and an angle of the diffraction grating; a FIFO memory controller configured to read continuing target diffraction grating angle data from the inner memory and input the continuing target diffraction grating angle data into FIFO when an amount of target diffraction grating angle data remaining in FIFO reaches a set value or less, wherein the FIFO memory controller inputs the continuing target diffraction grating angle data to FIFO memory during a polling period of the calculator.