Development of an active star repeater

The authors have developed a star repeater that performs optical regeneration and distribution of optically encoded digital data without optoelectronic conversions. Active integrated optics provide the key to implementing the repeater. With active integrated optics, optical signals can be amplified as they propagate through the waveguides, allowing scattering and absorption losses in the material to be offset so that branching networks do not attenuate the optical signals. The repeater is made up of two integrated optic devices. The devices are made of AlGaAs/GaAs and have a graded-index, separate-confinement-heterostructure, single-quantum-well epitaxial layer design that provides low intrinsic loss and high efficiency. Each device has a 1-to-10 active power splitter, ten electroabsorption modulators, and ten traveling-wave optical amplifiers, integrated on the same substrate. These devices transmit and amplify data bidirectionally, allowing operation as either a data distributor or a concentrator. A 5*5 repeater has implemented using two unit cells. The interconnections use single-mode, polarization-maintaining optical fiber to maximize TE mode gain through the active waveguides.<>