Abstract: A wavelength division multiplexed self-healing passive optical network using a wavelength injection method includes a central office for coupling modulated multiplexed optical signals (MMOS) and broadband optical signals (BOS)for an upstream light source into one signal transmitted to a plurality of optical network units (ONUs) through a working main fiber and a protection main fiber. A remote node connects to the central office via the main fiber and protection main fiber and to the ONUs through working distribution fibers and protection distribution fibers. The remote node demultiplexes the MMOS and the (BOS) for an upstream light source. The remote node transmits demultiplexed signals to the ONUs, which receive the modulated optical signals and the BOS for an upstream light source which corresponds to predetermined ONUs, and demodulate the modulated optical signals, and modulate upstream optical signals via demultiplexed BOS for an upstream light source.

Abstract: Process for the preparation of urea from ammonia and carbon dioxide in which the composition of the various process streams is measured via an ultrasonic measuring principle and in which the results of these measurements are used for process control. The process is particularly suitable for continuous measurements in a urea process.