Impact of ADC Bandwidth and Clipping Ratio on COF-PON Systems Based on Spatial Coding and Subcarrier Multiplexing

In this paper, we analyze the impact of analog-to digital convertor (ADC) bandwidth and clipping ratio on the performance of a 1 Gb/s x 15 user CDM-over-fiber-PON (COF PON) system based on 16-QAM modulation, spatial coding and subcarrier multiplexing. We consider the clipping ratio, resolution and bandwidth of ADCs with fixed sampling speed in both back-to-back and 25 km standard single mode fiber (SSMF) transmission cases, taking into account nonlinear propagation effects in fiber transmission. We find that the best error vector magnitude (EVM) performance can be achieved when a clipping ratio (CR) of 1.5-1.8 is applied for different ADC resolutions, and that in order to achieve an EVM of smaller than 0.12, an ADC with at least 5-bit resolution should be used.