DRoF incorporating multi-level modulation for radio-over-fiber

Digitized RF-over-fiber (DRoF) has been proposed as a high-performance low-cost solution for wireless signal distribution over optical fiber. However, the large overall optical data rate limits the implementation of DRoF for high frequency RF signals. Here, we propose a DRoF link using multi-level optical transmission to reduce the overall optical data rate and relax the requirements on the optoelectronic hardware while maintaining a relatively simplified architecture of base station. In this paper, a proof-of-concept experiment incorporating DRoF transport scheme with multi-level modulation is demonstrated. The results show that: (1) the fiber length has minimal impact on the performance of multi-level DRoF link; (2) optical links using RZ format have better performance comparing to using NRZ format; (3) an optical SNR above 11.5 dB results in a DRoF SNR of 20 dB; (4) a four-level modulation using RZ format is a promising solution to implement digitized RF-over-fiber transmission.