Configuring optical amplification modules and optical power splitting modules

A method comprising:

• arranging an input port configured to receive an optical wave;
• arranging a plurality of optical amplification modules, each configured to apply a gain to an optical wave propagating through that optical amplification module;
• arranging a plurality of optical power splitting modules, each configured to provide portions of an input optical wave to each output of two or more outputs according to an optical power splitting ratio associated with that optical power splitting module;
• arranging a plurality of optical ports, each configured to provide an optical wave;
• and
• configuring a tree network to interconnect the plurality of optical power splitting modules, the tree network comprising:
• a root stage of the tree network comprising a path segment between the input port and an input of a first optical power splitting module of the plurality of optical power splitting modules,
• a final stage of the tree network comprising a plurality of path segments between a respective output of an optical power splitting module and a respective optical port of the plurality of optical ports, and
• a plurality of inner stages of the tree network, each inner stage comprising a plurality of path segments between a respective output of an upstream optical power splitting module and a respective input of a downstream optical power splitting module;
• wherein at least two inner stages each include a respective optical amplification module on one or more path segments of the plurality of path segments of that inner stage.