To surely suppress the pattern jitter of an optical output signal and to obtain reduced pulse duty.

In the light transmitter for driving a semiconductor light emitting element (LD) in accordance with an input electric pulse signal and outputting an optical pulse signal, remaining carrier accumulated in the element LD immediately before light emission can be forcedly removed by temporarily applying reverse bias to the element LD in non-light-emission. Thereby the remaining carrier in the element LD is turned to '0' in succeeding light emission state independently of the data patterns '101', '1001' or the like of the input electric pulse signal, so that pattern jitter can surely be suppressed. When the pattern jitter is suppressed, required pulse duty can simply be obtained.