LASER BEAM WIDTH MEASURING INSTRUMENT USING INDUCTION BRILLOUIN SCATTERING

PROBLEM TO BE SOLVED: To make it possible to easily measure the laser beam width from a narrow laser beam width to a wide laser beam width and to simultaneously measure the single channel and multichannel laser beam widths by using a light having a frequency moved by induction Brillouin scattering in an optical fiber. SOLUTION: A first optical coupler 11 branches the light signal from a laser 10 to two signals and outputs these signals to an optical amplifier 12 and a second optical coupler 15. The optical amplifier 12 outputs the signal through an optical circulator 13 to the optical fiber 14 so that the induction Brillouin scattering can be induced within the optical fiber 14. The optical circulator 13 introduces the light to a second optical coupler 15 while minimizing the loss of the light. The second optical coupler 15 accepts the light of the moved frequency outputted from the C terminal of the optical circulator 13 at its input, accepts the original light signal to be measured from the first optical coupler 11 and generates howling by both. A photodetector 16 converts this signal to a howling spectral electric signal, outputs the signal to an analyzer 18 and measures the spectral width via a howling amplifier 17.