| 摘要 |
PURPOSE:To enable high-accuracy phase control over a light signal in optical communication and optical switching by varying the refractive index of the delay line of an optical waveguide made of a medium which varies in refractive index with an applied voltage, an impressed current, and temperature. CONSTITUTION:The light signal (a) is inputted to the optical delay line 1 and outputted to an output waveguide 4. At this time, part of the light is branched and its phase difference is compared by a phase difference detection part 3 with a reference phase; if the phase difference shifts from the setting, an error signal is outputted to a control part 2, which applies a control signal to the optical delay line 1 to vary its delay quantity. The optical delay line 1 consists of plural optical waveguides 1-1 - 1-4 and obtains the required quantity of variation in delay time. The optical waveguides are formed on a lithium niobate substrate. This medium varies in refractive index by being applied with a voltage, so the applied voltage is varied as the control signal. |
