The overall design of CFP optical module system

40Gbit/s CFP overall design of the optical module is mainly to solve the transmitting unit, the receiving unit implementation issues and control unit. Specific design methods are introduced each unit below.

In the transmitting unit, the selection of 10Gbit/s DML (directly modulated laser) as TOSA (light emitting component), laser driver integrated circuit chips within the drive. Laser driver receives a differential input data and provide a laser bias and modulation currents. Since the semiconductor laser slope efficiency will vary with changes in temperature, it is necessary to APC and extinction ratio compensation circuitry to achieve a stable laser average optical power. Lasers PD (photodiode) Monitoring LD optical output power and the output value of the feedback monitor PD to MCU (microcontroller), MCU by detecting feedback IBias values ​​to control the bias current output, thereby adjusting the bias Set circuit causes LD remains constant optical power output. Meanwhile, in order to avoid high-speed PCB (printed circuit board) on the other line interference on signal lines in the wiring of the signal differential signal transmission lines.

The receiving unit is mainly composed of PIN (photodiode) and TIA (transimpedance amplifier) ​​package together photodetector and limiting amplifier, thus completing the optical / electrical conversion. Four different wavelengths of light signals from each detector receives the appropriate wavelength and converts it into an electrical signal having a certain level, and then after the limiting amplifier signal power progressively larger, simultaneous extraction and recovery by the CDR circuit clock signal The signal received decision value dynamically created to allow data recovery and output.

The control unit uses MCU chip, through the acquisition of digital information for each of the corresponding port real-time monitoring of each channel voltage, temperature, laser bias current, input optical power and received optical power and reporting, in order to achieve the following three major functions: (1 ) communicate with the host computer system; (2) extracting module internal analog and digital information, testing, reporting and alerting; (3) modules within the various parameter settings intelligent control.