Patent ID: 8023541

Claim:
An optical transmission circuit comprising: a light emitting device having different temperature characteristics at low temperature and high temperature; differential switch transistors for driving the light emitting device, the differential switch transistors having sources connected to each other and drains connected to the light emitting device and a power supply, respectively; a bias current source for causing a bias current to flow through the light emitting device; a modulated current source for causing a modulated current to flow through the light emitting device; and a temperature compensation current source for controlling currents of the bias current source and the modulated current source so as to compensate for both temperature characteristics at low temperature and temperature characteristics at high temperature of the light emitting device, wherein the light emitting device is a surface emitting laser device, the surface emitting laser device having characteristics in which a threshold current causing a start of a current-light conversion increases and a current-light conversion efficiency decreases at the high temperature, and the threshold current causing the start of the current-light conversion increases and a current-light conversion efficiency decreases at the low temperature, and the temperature compensation current source has: a first temperature compensation current source for compensating for the high-temperature characteristics of the light emitting device; and a second temperature compensation current source for compensating for the low-temperature characteristics of the light emitting device, the temperature compensation current source changing characteristics of the bias current source and the modulated current source depending on the temperature such that the surface emitting laser device is compensated and a predetermined optical output power is constantly output.