Analog Response in Optically Powered Radio-Over-Fiber Links With Distributed Amplification in Single-Mode Fibers

Photonic systems with analog radio-over-fiber (ARoF) and power-over-fiber (PoF) technologies can transmit high-rate RF subchannels and energy to feed remote antenna units (RAU) and sensors. We introduce a one-fiber bidirectional link in ARoF-PoF systems based on standard single-mode fiber (SMF) to address the reception of RF signals from RAUs without using remote lasers. This so-called hybrid setup complements the classical forward architecture used for transmitting signals remotely. This work exploits the transmission of high power at the SMF's lowest attenuation wavelength in both setups based on an erbium-doped fiber amplifier (EDFA) to generate the feeding light at 1550 nm in addition to the commonly used Raman laser operating in the S-band. Analog metrics quantify the overall impact of the optical high-power in the RF signal due to Raman amplification, amplified spontaneous emission (ASE) noise, pump noise transfer, and fading caused by the chromatic dispersion of the fiber. Improvements of 57 dB in RF gain, 43 dB in noise figure, and 28 dB in dynamic range are achieved for a 5-GHz signal under 3.5 W of injected optical power in the hybrid setup, compared to the values for the no-pump state. Experimental measurements are compared to analytical curves under different operating conditions in a 10-km SMF link. Despite the good fit for most results, the RF signal is noisier than expected for pump powers above 1.8 W in the hybrid configuration. Better optical transmission efficiency is obtained when the EDFA is used to generate power in the optical C-band.