Sub-Devices

With MT-FIMMPROP creating large waveguide devices/ circuits, there are more opportunities to find efficiency gains through symmetry and repetition in your design. This can be achieved with a sub-device.

A sub-device is a component simulation which can be copied around the MT-FIMMPROP canvas. When the full circuit is simulated, the sub-device is evaluated just once and the result copied to all repetitions. Sub-devices can also be flipped allowing symmetric simulations to be cut in half.

Coupling regions between the rings and the waveguide bus are created using sub-devices. This reduces five more taxing simulations down to just two for this device. Straight waveguides and constant curvature bends require just one mode list so are near instant relative to structures where the cross section varies which require multiple mode lists.

Additionally, each coupling simulation is symmetric meaning the sub-device can be just half of the coupling region cut down its axis of symmetry, further halving the number of modelists needed to be simulated.

Without sub-devices, this set of cascaded MMIs would contain 14 demanding simulations from its bend sections and 7 copies of the same MMI; in other designs MMI’s may require a large number of modes or even include a taper as they do in this example.

As sub-devices can be flipped, with only 3 unique bends and a single MMI as a sub-devices we can describe the entire device.