Bidirectional fibre=optic telecommunications system - has divergent laser focussed on annular receiver formed by fibre=optic core

摘要

The device is for use with radiant energy systems such as fibre optic cables comprising an energy source (5) such as a semiconductor laser emitting a divergent beam coupled through an anamorphic lens system (9) to a receiver which is typically the outer annular zone (5) at a two-way fibre optic (f). The fibre optic core (fi) is connected in normal fashion to a diode detector (D). The anamorphic lens system (9) comprises an optical collimator (L1) converting the source beam into a parallel beam, a deviator (DE) transforming the parallel beam into a divergent annular beam, and a refocussing optic (L2) focussing the beam as an annular beam on the annular- zone of the receiver. The collimator and refocussing optics are Fresnel lenses. The deviator may be of moulded plastic, an optical system of symmetrical revolution or such as a Fresnel prism. The arrangement may be reversed with the source and detector interchanged.