| Popis: |
In optical submarine systems there may be a requirement for branching units (BU) in the trunk path, these devices allow traffic to be sent from the trunk to a spur and vice-versa. In single channel systems this is a simple task of routing the entire fibre to a spur. In WDM systems, routing functions can be realized by dropping and adding wavelengths from a trunk to the spur. This operation can be achieved by a different type of BU utilizing gratings as wavelength selective filters, and circulators to allow selective channels to be dropped. The main problem with this simple approach is that it requires one fibre for each add and drop channel resulting in four fibres (two fibre pairs) from a single fibre pair trunk. Moreover the BU would have a significant loss associated with it. We propose an alternative novel solution which can multiplex the add and drop elements from different trunks onto one fibre pair, and also incorporates gain elements, not only to compensate for the device losses but also to provide the channels with appropriate gain. (5 pages) |
