A Remote Power-Feeding System with Converters Fed with Constant Current used for Optical Fiber Systems

For the first 140-Mbit/s optical waveguide link in the long-haul network of the Deutsche Bundespost a new power-feeding system has been developed. On part of the route linking Hamburg and Hanover, three intermediate regenerative repeater stations are housed in underground containers. They are remotely powered via their own power cable laid alongside the optical cable. Two series-connected power-feeding units per power-feeding circuit supply a constant current of 400 mA. At the regenerative repeater stations, converters convert this current into a constant voltage of nominally 60 V. As up to five regenerators can be connected to each route converter, up to 60 optical fiber systems can be supplied with power via the 24-wire power cable. The high power-feeding voltage (max. ±700 V) is only switched on after the feeding circuit has been automatically tested for continuity with a low voltage of 40 V and opposite polarity. Interruptions during service lead to immediate reduction of the high power-feeding voltage and indication of the faulted section. If the balance of the normally floating route is disturbed by a ground short, the power-feeding current is like-wise disconnected. Hazard to persons is thus precluded at all times. The line power converters fed with constant current on the route are a new combination of a step-up switching regulator (boost converter) and an uncontrolled forward converter. The constant input current is converted into a constant voltage, from which the isolated output voltage is then generated.