Sound Alerter Powered Over an Optical Fiber

The potential introduction of lightguide connecting residential and commercial premises to central switching offices offers exciting possibilities for communications users. The availability to each customer of hundreds of megahertz of inexpensive switchable bandwidth could revolutionize telecommunications. One cost barrier to the employment of lightguide in the local loop would be eased if the guide could also be used to provide the essential functions of ordinary telephone service without requiring metallic wires to carry electrical power to the telephone. The possibility would then exist for introducing a lightguide telephone system; the essential functions of this system would be powered from central offices, and broadband services could subsequently be added to it in a cost-effective manner. The broadband services and non-essential telephone services could be locally powered. 3309 The largest technical uncertainty limiting the consideration of dielectric lightguide for ordinary telephony is power: Can telephone operating power requirements realistically be met by photovoltaic conversion of optical power emergent from the lightguide? Since the largest power demands in a conventional telephone occur when the bell is rung, we have given first priority to investigating the power efficiency of an optically driven sound alerter. The other essential functions--speech signaling and recognition of the telephone hook status--will be discussed in a subsequent report.