Waveguide substrates and waveguide substrate assemblies having waveguide routing schemes and methods for fabricating the same

A waveguide substrate comprising:

• a first surface and a second surface;
• a plurality of waveguides within the waveguide substrate, wherein:
• the plurality of waveguides defines a plurality of inputs at the first surface;
• a subset of the plurality of waveguides extend to the second surface to at least partially define a plurality of outputs at the second surface;
• at least one branching waveguide extending between the first surface to a surface other than the second surface,
• wherein the at least one branching waveguide is a drop-waveguide;
• an add-waveguide extending between the second surface and a surface other than the first surface;
• a first input alignment feature and a second input alignment feature within the first surface, wherein the plurality of inputs is disposed between the first input alignment feature and the second input alignment feature;
• and
• a first output alignment feature and a second output alignment feature within the second surface, wherein the plurality of outputs is disposed between the first output alignment feature and the second output alignment feature.

A waveguide substrate comprising:

• a first surface and a second surface;
• a plurality of waveguides within the waveguide substrate, wherein:
• the plurality of waveguides defines a plurality of inputs at the first surface;
• a subset of the plurality of waveguides extend to the second surface to at least partially define a plurality of outputs at the second surface;
• and
• at least one branching waveguide extending between one of the first surface and the second surface to a surface other than the first surface and the second surface,
• a first input alignment feature and a second input alignment feature within the first surface, wherein the plurality of inputs is disposed between the first input alignment feature and the second input alignment feature;
• and
• a first output alignment feature and a second output alignment feature within the second surface, wherein the plurality of outputs is disposed between the first output alignment feature and the second output alignment feature,
• wherein the at least one branching waveguide comprises:
• at least one first drop-waveguide extending from the first surface to a third surface of the waveguide substrate;
• at least one second drop-waveguide extending from the first surface to a fourth surface of the waveguide substrate opposite from the third surface;
• at least one third drop-waveguide extending from the first surface to a fifth surface of waveguide substrate;
• and
• at least one fourth drop-waveguide extending from the first surface to a sixth surface of the waveguide substrate opposite from the fifth surface.