Figure 9
From: A low cost, short range quantum key distribution system
The six state QKD receiver, (a) shows a schematic of the layout, including the fold mirrors to ensure the output ports are on the perimeter of the optics box. (b) shows the actual device, with the optical path superimposed. Note the beamsplitters are all on tip/tilt stages (Newport MM-075-HEX-M), to allow for fine corrections to alignment