G02B 6/2861

Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals {forming multipart couplers without wavelength selective elements, e.g. "T" couplers, star couplers using fibre optic delay lines and optical elements associated with them, e.g. for use in signal processing, e.g. filtering }