Optically Powered Speech Communication Over a Fiber Lightguide

Abstract

The photovoltaic conversion of optical power transmitted over a fiber lightguide can supply electrical power to low-drain semiconductor devices in remote locations. Acoustic powers comparable to those of conventional telephone ringers have been produced <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup> in this way by using a fiber-coupled GaALAs photovoltaic detector <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> to excite an electroacoustic tone generator. It was conjectured1 that the electrical power for other telephone functions-transmit/receive, dialing, and hook-status recognition-could also be optically supplied, but the signaling techniques appropriate to a dielectric fiber were left unspecified. This note describes the implementation of two-way speech communication between an electrically powered local station and an optically powered station located at the remote end of a 1.1-km-long, single-strand, optical fiber. The remote-station sound alerter has also been operated over this link.