Abstract: Power of multi-path interference light is measured by setting the cycle of pulse modulation for a light source in correspondence with the length of an optical medium of a target to be measured, by inputting pulse light after being modulated to the target to be measured, by modulating the pulse signal light output from the target to be measured with the use of a pulse signal for modulation having the same cycle as the set cycle, and by observing the wavelength dependency of the power of the light after being modulated. In this way, a modulation condition is set according to a condition of a target to be measured when multi-path interference light caused by double Rayleigh scattering light or reflection at the end of a connector is measured with a pulse-OSA method, so that measurement accuracy is improved.

Abstract: The present invention relates to a device for optical amplification, and a primary object of the present invention is to provide a method and device for optical amplification which can maintain the wavelength characteristic of gain constant and can obtain a wide input dynamic range. The device according to the present invention includes a first optical amplifying unit having a Raman amplifying medium and a first pump source for pumping the Raman amplifying medium, and a second optical amplifying unit optically connected to a rear stage of the first optical amplifying unit. The second optical amplifying unit has an optical amplifying medium and second pump sources for pumping the optical amplifying medium. The present invention is characterized by a control unit for controlling the gain of the first optical amplifying unit so that variations in output power of the first optical amplifying unit due to variations in input power of the first optical amplifying unit are canceled.