{"id":356474,"date":"2024-03-11T17:43:42","date_gmt":"2024-03-11T17:43:42","guid":{"rendered":"\/forum\/forums\/topic\/edge-coupler-sin-waveguide-to-smf-fiber-strange-field-problem\/"},"modified":"2024-03-11T17:43:42","modified_gmt":"2024-03-11T17:43:42","slug":"edge-coupler-sin-waveguide-to-smf-fiber-strange-field-problem","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/edge-coupler-sin-waveguide-to-smf-fiber-strange-field-problem\/","title":{"rendered":"Edge Coupler SiN waveguide to SMF fiber Strange Field Problem"},"content":{"rendered":"

Hello, I am trying to simulate SiN waveguide to SMF and extract the S parameters or just see the transmission into the fiber mode to get the coupling loss. <\/p>\n

I do not use ports because I break up the simulation into two parts and ports cannot export\/import sources. I followed this example to perform the export\/import: https:\/\/optics.ansys.com\/hc\/en-us\/articles\/360034383034-Using-monitor-data-to-define-the-spatial-field-profile-of-a-source-in-FDTD<\/p>\n

Part 1) The inverse taper in the SiN waveguide to convert\/expand the mode to better match MFD of the fiber. I use a mode source going towards the fiber from the nominal WG width and I export the fields just before the interface to the fiber.<\/p>\n

Part 2) The WG to SMF interface. On the PIC side, I import the source using the export from part 1. On the fiber side, I have modal expansion and DFT monitors tied together to get the transmission into the fiber mode.<\/p>\n

My original modal source for part 1 is the fundamental TE mode (it’s TE mode WG), I set wavelength from 1.5um to 1.6um, my mesh setting is “3” and I <\/p>\n

When I try to change the inverse taper to help me design the coupler and find the correct length, sometimes I get reasonably results, but mostly I don’t. See these videos:<\/p>\n

300um taper 1500nm to 250nm: https:\/\/youtu.be\/4w1wdh_IBDY<\/p>\n

200um taper 1500nm to 250nm: https:\/\/youtu.be\/cDQYOpT9qME<\/p>\n

100um taper 1500nm to 250nm: https:\/\/youtu.be\/8mfLJqDixOg<\/p>\n

The 300um one works as I expect and I get reasonable result at the end (total transmission into fiber mode ~50% or -3dB). However the 200um and 100um I get a very long simulation where a strange field grows from the PIC side. You can easily see in the videos at the end. This field can’t be physical and I must have something set incorrectly, any ideas?<\/p>\n

Also, you can see all the videos the majority of the time nothing is happening. Is there any way to speed this up and simulate only the important parts?<\/p>\n

Thank you,<\/p>\n

George<\/p>\n","protected":false},"template":"","class_list":["post-356474","topic","type-topic","status-closed","hentry"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t