Wideband, Bidirectional Lightguide Communication With an Optically Powered Audio Channel

The feasibility of bidirectional speech-television communication over a single-strand lightguide, with emergency optical powering of the remote station telephone, has been demonstrated. The remote circuits drew ∼250 μA at 0.9 volt from a double-heterostructure photovoltaic detector at 0.65 mW of received optical power; the detector low-pass response into 50 ohms was down 6 dB at 60 MHz. The optical packages featured GRIN-lens bidirectional couplers and, at the remote station, a low-threshold-current, buried-heterostructure laser.