A new form of optical-fibre data-highway telemetry system enables a large number of separate data sources to be input anywhere along the fibre cable, without involving optical connections

Phase-modulated data transmission in multimode optical fibres is complicated by signal fades due to variations in intermodal phase. The letter describes a very simple technique to recover the data without the use of complex diversity receivers. The method involves varying the relative modal phases at a rate sufficient to ensure at least one signal maximum during each bit period. Thus the input sig...

Reliable detection of a phase-modulated optical carrier has been demonstrated over 500 m of graded-index optical fibre using a semiconductor-laser source and mode-mode interference. The system performance is limited by the noise and spectral properties of the optical source. Spectral measurements indicate that transmission over several kilometres should be possible. This has direct significance for amplitude-modulated systems with semiconductor-laser sources as it implies that modal noise can occur at fibre connections up to several kilometres from the optical source