| 摘要 |
The invention provides a branching unit for a wavelength division multiplex optical communication system. The branching unit has at least an input for a trunk input fibre, an output for a trunk output fibre, and one or more branch inputs or outputs, each for connection to a branch fibre. The branching unit comprises an amplified add/drop multiplexer, which has two or more doped fibre optical amplifiers (21, 22, 23) and a pump laser section comprising two pump lasers (31, 32) for pumping the optical amplifiers. A fibre optic coupler (33) is provided to split the output of the pump laser section and to route a first part along fibre (34) towards the first doped fibre amplifier (21, 22) and the second part along fibre (35) towards the second doped fibre amplifier (23). The arrangement is adapted such that the signals passing straight through the branching unit along the trunk fibre will be amplified, and that signals passing between the trunk fibre input or output and one of the branch inputs or outputs will also be amplified, in both cases the pumping for the amplifier being provided by the pump lasers (31, 32) of the pump laser section. This arrangement allows for use of the minimum number of pump lasers to achieve redundancy, and also allows for optimisation of gain and noise characteristics. |
