Patent ID: 6697400
Filing Date: 2004-02-24
Classification: H01S

Abstract:
A circuit for driving a laser diode which has a feed-forward type APC circuit in an optical transmitter supporting burst mode, comprising:a laser diode for emitting transmission signal light; a driver circuit for driving said laser diode according to a burst input signal; a pulse current control circuit for controlling pulse driving current for said laser diode according to the burst input signal by said driver circuit; a bias current control circuit for controlling bias driving current for said laser diode; an average value detector circuit for detecting the average value of the burst input signal and outputting the value corresponding to a mark rate; a temperature detector circuit for detecting a surrounding temperature of the optical transmitter and outputting a result of it; and a memory control circuit connected to plural memories for storing data having different characteristics with respect to the value corresponding to the pulse driving current for said laser diode and the value corresponding to the bias driving current for said laser diode according to the surrounding temperature of the optical transmitter, wherein said plural memories include a first memory stored with a characteristic of a steep slope of the driving current corresponding to the temperature, a second memory stored with a characteristic of a gentle slope of the driving current corresponding to the temperature, and a third memory with a characteristic of a more gentle slop of the driving current corresponding to the temperature, and wherein said memory control circuit selects one of said first memory, said second memory and said third memory in this order, corresponding to a magnitude of the mark rate from said average value detector circuit, reads out the value corresponding to the pulse driving current for said laser diode and the value corresponding to the bias driving current for said laser diode according to the surrounding temperature of said optical transmitter, and controls the light output and the quenching rate of said laser diode to be constant by adjusting the pulse driving current and the bias driving current.