Patent ID: 7539424
Filing Date: 2009-05-26
Classification: H04B

Abstract:
1. A burst mode optical receiver comprising: a photodiode, which receives an optical signal and converts the optical signal into a current signal; a pre-amplifier, which converts the current signal into a voltage signal, amplifies the voltage signal with a gain according to a control signal, and outputs an amplified signal, the pre-amplifier comprising an impedance control unit which controls an impedance of the pre-amplifier in response to the control signal and an amplifying unit which converts the current signal into the voltage signal and amplifies the voltage signal with a gain corresponding to said impedance controlled by the impedance control unit; a first peak detector, which detects a top peak voltage and a bottom peak voltage of the amplified signal and outputs an average value of the detected top peak voltage and the detected bottom peak voltage as a first reference voltage; the gain controller, which compares the first reference voltage with a comparison voltage and outputs the control signal which controls a gain of the pre-amplifier according to the comparison result, the control signal having a first level when the first reference voltage is lower than the comparison voltage, and the control signal having a second level when the first reference voltage is higher than the comparison voltage; a first limiting amplifier, which receives the amplified signal and the first reference voltage and amplifies a difference between the amplified signal and the first reference voltage; and a buffer, which buffers a limitedly amplified signal from the first limiting amplifier, wherein, when the control signal of the first level is generated from the gain controller, a transistor of the impedance control unit is turned on to decrease a trans-impedance of the pre-amplifier and, when a control signal of the second level is generated from the gain controller, the transistor is turned off to increase the trans-impedance of the pre-amplifier.