METHOD FOR CONTROLLING EXTINCTION RATIOS OF LASER DIODES, LASER DIODE DRIVING CIRCUIT, INTEGRATED CIRCUIT THEREOF, TRANSMITTER APPARATUS, AND COMMUNICATION SYSTEM

摘要

There is disclosed a technology for allowing the extinction ratios of laser diodes, in a optical transmission in which data intermittently occur, to be controlled even when the current/light conversion characteristics of the laser diodes vary with environmental temperatures or aging degradations. According to the technology, the mark ratio of intermittently occurring burst signals is measured (S301), and the current/light conversion efficiency is determined from the average output power variation, from a laser diode, which are caused by variation of the mark ratio for each of the burst signals (S310). This current/light conversion efficiency is compared with a reference value (S320), and if they are not coincident with each other, a modulated current is modified (S322,S324). An average output power is calculated based on the mark ratio and the measured value of average output power (S330) and then compared with a reference value (S340). If they are not coincident with each other, a bias current is modified (S342,S344). Repetition of the modulated current control and bias current control can keep the extinction ratio of the laser diode constant.