At a first glance it seems like you have not set the laser frequencies in your business, residential and school mall sub systems. Once I changed them to 1310, 1330, 1350 nm the example with mux-demux design seems to work correctly. The issue with the bidirectional splitter needs further investigation however you should be able to complete your design with the fix I suggested.
This error usually occurs when the simulator cannot find a DC solution for the first time step. This can be very challenging when you have multiple transistors in a circuit. Instead of starting your voltage or current sources from a certain value you can try to ramp them up slowly (using Vpulse or Ipulse) during the transient simulation.