Externally modulated laser driver with integrated clock and data recovery

The ONET1131EC, from Texas Instruments, is a 2.5V EML modulator driver with transmit clock and data recovery (CDR) designed to operate between 9.8Gbps and 11.7Gbps without the need for a reference clock. CDR bypass mode can be used for operation at lower data rates and a two-wire serial interface allows digital control of features like output polarity select and input equalisation. The transmit path consists of an adjustable input equaliser for equalisation of up to 300mm of microstrip or stripline transmission line of FR4 printed circuit boards, a multi-rate CDR and an output modulator driver. Output waveform control, in the form of cross-point adjustment and de-emphasis, is available to improve the optical eye mask margin. The device provides bias current for the laser and an integrated APC loop to compensate for variations in average optical power over voltage, temperature and time. The device contains internal analog to digital and digital to analog converters to support transceiver management and eliminate the need for special purpose microcontrollers.