Long-range wireless optical power transfer system using an EDFA

A wireless optical power transfer (WOPT) system using an erbium-doped fiber amplifier as an optical power source is proposed to achieve long range, high power, and hazard-free power delivery in the air. The transmitter generates a wide band of amplified spontaneous emission around the central wavelength of 1550 nm. A wavelength division multiplexing (WDM) filter (λ=1552.25 nm) is deployed to obtain a safe narrowband beam illuminating the receiver units. A ball lens retroreflector reflects a small portion of the incident beam back to the transmitter, establishing a closed ring resonance loop. An improved safety mechanism is proposed to terminate the resonance when an obstacle blocks the transmitter-receiver line of sight. The measured incident power of 1 W decreases to 0.79 mW after the WDM filter is deployed which is well within defined maximum permissible exposure standards. For the demonstration of free-space transmission, transmitter-receiver separation is extended to 30 m. The experimental results show that a single-channel WOPT system provides an optical power of 400 mW with a channel linewidth of 1.027 nm over 30 m and an electrical power of 85 mW is acquired using a gallium antimonide photovoltaic.