| 摘要 |
PURPOSE:To make an amplitude of an optical output signal always constant by using a PLZT thin film total reflection type optical switch having a rgion whose transmission characteristic is saturated to a drive voltage as an optical modulator and applying a drive voltage exceeding a voltage required for the switching through AC coupling. CONSTITUTION:A light output from an LD 1 is led to an optical input terminal (b) of a PLZT thin film full reflection type optical switch 3. On the other hand, a PCM signal is amplified by an AC amplifier 41 of a drive circuit 4, its mean value is biased by a bias voltage fed from a bias generating circuit 5 and the result is fed to a drive signal input terminal 31. Then the LD light led to an optical input terminal (b) is subject to intensity modulation by the switch 3 and sent from an optical output terminal (d) via an optical fiber 22. When the drive voltage is a prescribed value or over, since the switch is operated stably, even if the center level of the drive voltage is fluctuated more or less, the optical switch is operated stably. |
