Patent ID: 9503195
Filing Date: 2016-11-22
CPC Classification: G02F,H04B

Claim Text:
1. A working point controlling device to be used with an MZ modulator, comprising a light modulator for performing phase modulation to an input data signal, and further comprising a transimpedance amplifier, a low-noise amplifier, a high Q band-pass filter, a first power level conditioning, a micro processor and a second power level conditioning that are connected in an order, wherein: the transimpedance amplifier is configured to convert current output by a Photodetector (PD) of the MZ modulator into a voltage signal; the low-noise amplifier is configured to detect and amplify a low-frequency signal component of the voltage signal in order to improve the signal/noise ratio of the system; the high Q band-pass filter is configured to filter off a desired low-frequency signal from the amplified low-frequency signal component of the voltage signal to obtain a light detection signal of a subsequent low-frequency square signal to be input into the MZ modulator; and configured to detect and amplify an error signal in order to improve the signal/noise ratio of the system; the first power level conditioning is configured to perform power level condition on the error signal of a phase so that the signal output falls into an input range of Analog-to-Digital (A/D) conversion; the micro processor is configured to generate the subsequent low-frequency square signal and to perform software synchronous detection and Proportional Integral (PI) adjusting algorithm; and the second power level conditioning is configured to perform condition to the voltage output by Digital-to-Analog (D/A) conversion so that the D/A output is able to meet DC bias whole controlling range power voltage of the MZ modulator and to convert the generated subsequent low-frequency square signal into a low-frequency square signal having small amplitude and the DC signal output into a DC bias full-control range of the MZ modulator and superimpose the low-frequency square signal having small amplitude and the DC bias full-control range of the MZ modulator.