Optical Signal Processing for W-Band Radio-Over-Fiber System With Tunable Frequency Response

Tunable frequency response is designed and experimentally demonstrated in this paper. The performance of frequency response in proposed radio-over-fiber (RoF) systems is investigated in terms of theoretical analysis, simulations, and experimental results with various fiber transmission distances. The notch in frequency response can be easily circumvented by changing the oriented angle of polarized lightwave in the proposed direct detection (DD) scheme. For comparison, the conventional Mach-Zehnder modulator (MZM) based DD scheme suffers from fixed frequency notch at certain frequencies, which generates forbidden frequency bands for W-band signal delivery. Our experimental results show that the proposed DD scheme exhibits a stable EVM performance of the 16-QAM signal from 83 GHz to 87 GHz via 25-km standard single-mode fiber (SSMF) and 1-m wireless transmission. On the contrary, the conventional MZM-based DD scheme encounters severe signal degradation at 85 GHz and 86 GHz. In this paper, the proposed scheme is implemented to demonstrate full bandwidth availability within a desirable frequency range by tuning the frequency response. Furthermore, a 10-Gbps 16-QAM signal located at 85 GHz is successfully transmitted by the proposed DD scheme which can provide 10-gigabit data transmission under 5G requirement.