Abstract: This invention is applied to an optical amplifier evaluation method of modulating by an optical modulator 23 light output from a light source 1 into a rectangular optical signal which is enabled/disabled in a predetermined period, then applying the optical signal to an optical fiber amplifier 2 to be measured, and obtaining the gain and noise figure of the optical fiber amplifier from the light intensities in the ON and OFF periods of an optical signal output from the optical fiber amplifier and the light intensity in the ON period of an optical signal input to the optical fiber amplifier. Output light from the optical fiber amplifier in a no-input state is passed through an optical path extending from the light source to the optical fiber amplifier and an optical path extending from the optical fiber amplifier to a light intensity measurement position, thereby obtaining optical losses on the respective optical paths. By the obtained optical losses, the light intensities are corrected.

Abstract: In an optical measuring apparatus, a laser beam is transferred to a diffraction grating so that the laser beam is spectrally separated into respective wavelength components. The wavelength components are sequentially guided into a polarizing optical element in which the respective wavelength component are separated into S and P polarized components, when the diffraction grating is rotated. The S and P polarized components of the respective wavelengths are detected by photodetectors and electrical signals from the photodetectors are supplied to a signal processing unit. In the signal processing unit, the electrical signals corresponding to the P and S components are corrected with a spectral efficiency characteristic of the grating, a percent loss characteristic of the polarizing element and photoelectro conversion characteristics of the photodetectors and the corrected signals are analyzed to obtain an absolute value of the laser energy for the respective wavelength.

Abstract: A driving circuit for rotating the grating of a monochromator thereby changing the wavelength of light which is emitted from the monochromator. This driving circuit includes an operating panel for supplying wavelength data, a data converting circuit which obtains a trigonometric function value corresponding to the wavelength data when the data converting circuit receives the wavelength data, and which converts the wavelength data to angle data on the basis of the trigonometric function value, and a motor driver for rotating the grating into the angular position corresponding to the angle data.