Coupler for optical communication system

Claim 1

In an optical communication system having a plurality of optical signal transmission lines each comprising at least one optical waveguide having an acceptance angle theta , a coupler for coupling a portion of the optical signal propagating in any one of said transmission lines to each of the remaining transmission lines, said coupler comprising support means for disposing the end portions of said optical signal transmission lines in a parallel bundled array having a maximum cross-sectional dimension D, the optical waveguides of which said transmission lines are comprised terminating in faces that are disposed in a substantially planar array, thereby constituting a transmission line bundle endface, and concave light reflecting means spaced from said endface and being so disposed with respect to said endface that a portion of the optical signal radiating from any one of said optical signal transmission lines reflects from said reflecting means back into each of the remaining optical signal transmission lines, said reflecting means being symmetrical about an axis that passes through the center of said array, said reflecting means including a light reflecting surface, the cross-sectional shape of which is given by the equation y (4px)1/2(1 - kx)1/2 where k is given by -1/(2p) < OR = k < OR = 1/(2p) and p is determined by the equation p D/2 tan theta said acceptance angle theta being an angle up to 12*.