ELECTRO-OPTICAL SAMPLING OSCILLOSCOPE

PROBLEM TO BE SOLVED: To provide an electro-optical sampling oscilloscope wherein the configuration of an optical system is simplified for smaller device. SOLUTION: A light-emitting circuit 20 which emits a reference laser light La0, a directional coupler 22 comprising such function as emitting the reference laser light La0 to one end surface of an optical fiber 23, an electro-optical crystal 28 which changes its refractive index according to the electric field due to a measured signal coupled through a metal pin 27, a reflection mirror 29 which reflects the reference laser light La0 as a signal light La1, a reflection plate 30 which reflects the reference light La0 as a reference light La2, and a light- receiving circuit 32 which converts a signal light La3 into an electric signal, are provided.