The Fiber Port Clusters are compact opto-mechanical units that combine two fiber-coupled sources with same wavelengths and then splits the combined radiation into multiple output fiber cables with high efficiency and variable splitting ratio.
The two input ports are fiber-coupled to PM fiber cables. Polarizers define the input polarization which is necessary for a long term stable splitting ratio.
Two photo diodes right after each input port allow for a continuous monitoring of the radiation. The two input sources are superimposed by means of a polarization beam splitter.
Subsequently, the radiation splitting is achieved by using a cascade of rotary half-wave plates in combination with polarization beam splitters. By use of the rotary half-wave plates, almost any desired splitting ratio can be achieved, see the tech note FiberPortCluster_2-6_Balancing.pdf for the limitations.
At the output ports further polarizers are placed in order to define the polarization at output of the system.
A fundamental component of a Fiber Port Cluster is the Laser Beam Coupler, which is the input into the opto-mechanical unit collimating the input radiation and, finally, couples the radiation back into the polarization-maintaining fiber cables. The stability of the total Fiber Port Cluster is determined by the stability of the laser beam coupler.