The issue here is with the use of the Delay component and the settings of the Travelling Wave SOA component. The settings for the SOA were not giving any output, so you will want to make sure that they are correct. Open up the component properties, by double clicking the SOA, and then click on the Help button for more detailed information.
The Delay component is generally used on one of the inputs of a bidirectional component to allow a backwards propagating signal to reach it on a subsequent iteration. For more information on how the Delay component and iterations parameter work take a look at this forum post:
Bidirectional Components [Optical System]
To fix your project file the Delay component between the Travelling Wave SOA and Photodetector APD was removed. The Travelling Wave SOA was removed and replaced with an Optical Amplifier. The number of iterations was also increased from 3 to 9, to allow the system to converge.
Hope this helps!