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 radiation 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 stability of the laser beam coupler.