Patent ID: 7715728

Claim:
An optical transmitter comprising: a light-emitting element; a driving circuit that causes, based on an input signal, the light-emitting element to emit an optical signal having a pulse shape; a temperature detection unit that detects an ambient temperature of the light-emitting element; a storage device that stores temperature characteristics information of the light-emitting element, the temperature characteristics information stored in the storage device being information in which ambient temperatures of the light-emitting element and driving currents flowing into the light-emitting element are associated with each other; and a control circuit that controls the driving circuit based on the ambient temperature detected by the temperature detection unit and the temperature characteristic information stored in the storage device, so that an extinction ratio of the optical signal having the pulse shape becomes substantially constant; wherein a relation between the ambient temperatures of the light-emitting element and modulation currents satisfies Δ I =( k·ΔP /η(θ)) where ΔI denotes the modulation current, η(θ) denotes a slope efficiency of the light-emitting element at an ambient temperature θ, ΔP denotes a difference between a light intensity of the light-emitting element when the input signal takes a H level and a light intensity of the light-emitting element when the input signal takes an L level and 0.2<k<2.