Study on the Compensation of Silicon Photonics-Based Modulators in DCI Applications

For next generation high speed optical coherent systems, digital pre-emphasis filters are essential as they can pre-compensate for the transmitter frequency response and mitigate receiver noise enhancement. However, the downside of using full pre-emphasis to completely pre-compensate for the low bandwidth transmitter is that it increases the signal peak-to-average power ratio (PAPR), thus posing a higher effective number of bits (ENoB) requirement for the digital to analog converter (DAC) and increases optical modulation loss. In this paper, we study the impact of partial pre-emphasis filters on signal PAPR and show how partial pre-emphasis reduces DAC ENoB requirements and MZM modulation loss. Our proposed scheme reduced the DAC ENoB requirement from 5 to 4.5 bits at the same implementation SNR. This enables a lower optical module power through the reduction of DAC and driver amplifier (DA) power. The experimental results, for single-pol case for a partial pre-emphasis filter, showed that the system bandwidth can be extended from 10GHz to 20GHz and tolerate a 6dB loss for a 0.4dBQ penalty factor, and a 0.8dB PAPR reduction.