Fiber Optic Ring-Lan Design with Improved Reliability through the Use of Four-Port Couplers,

Fiber optic ring-LANs are sensitive to failures in the cable or in the equipment. One can prevent network breakdown due to equipment failure if optical four-port couplers are provided as a bypass. Also, by taking advantage of state-of-the art digital signal processing techniques with high dynamic range, unwanted disturbing signals can be suppressed as long as a minimum SN ratio is maintained. Since the worst case amplitude of the disturbing signal can be calculated, this required SN ratio results in a reasonably low value.