A predistortion circuit design technique for high performance analogue optical transmission

In radio over fiber systems, a highly linear optical transmitter is necessary to achieve the required signal dynamic range. In order to compensate for second and third order laser distortions, quadratic and cubic law circuits are usually required to work at up to 2 or 3 times the carrier frequency due to their nonlinear property. This paper presents an alternative design approach that uses multiple tank circuits to relieve the bandwidth requirement at the same time providing tunability to account for component variation, thermal effect and aging of semiconductor lasers. A laser pre-distorter example that works at 2 GHz range with about 300 MHz bandwidth was designed using standard CMOS technology. The average reductions of 20-30 dB for the 2nd and 3rd order harmonic distortion can be obtained in simulation.