Optical Hybrid Fiber/Free-Space and 25 GHz Wireless Transmission using LTE M-QAM Signals

We experimentally demonstrate a seamless hybrid transmission of radio-over-fiber (RoF), radio-over-freespace optics (RoFSO) and millimeter wave wireless link using long-term evolution (LTE) 4/16/64-QAM signals for broadband wireless access applications. The signals are transmitted and evaluated over the hybrid channel consisting of 5 km of standard single-mode fiber (SMF), 2 m FSO under the turbulence level up to $3.2\times 10^{-11}\mathrm{m}^{-2/3}$ and 3.3 m25 GHz wireless channel. The performance shows that, the error vector magnitudes (EVM) are below the 3GPP standard for 4/16/64-QAM signals. We show that, the bit error rate (BER) for all signals is below the forward error correction limit of 10-3. We also perform simulation analysis at higher bit rates of 10 and 15 $\mathrm{G}\mathrm{b}/\mathrm{s}$ for the hybrid link of SMF (5 km) and FSO (extended up to 500 m) under the turbulence level of 1$.3\times 10^{-15}\mathrm{m}^{-2/3}$ for the practical outdoor scenario. We achieved acceptable performance for 4- and 16-QAM at 10 and 15 Gb/s.