| 摘要 |
PROBLEM TO BE SOLVED: To provide a light output control circuit in an optical communication system capable of shortening a time until a prescribed light output can be obtained after start. SOLUTION: Driving currents corresponding to the discrete value of a light output control counting circuit (counting circuit) are supplied to a light emitting element, the monitor voltage of the output light level of the light emitting element is compared with a reference voltage, the counting direction of the counting circuit is controlled according to the compared result so that the driving currents can be controlled so as to be required driving current, and a counting initial value is set in the counting circuit. This light output control circuit is provided with a step control circuit for setting a counting step in the counting circuit so that the counting step to be set in the counting circuit after start can be decided according to the size of the discrete value of the counting circuit. When a counter clock is counted the prescribed number of times by the step control circuit, the counting step of the counting circuit is set in an LSB. |
