{"id":433022,"date":"2025-05-31T13:09:37","date_gmt":"2025-05-31T13:09:37","guid":{"rendered":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/simulation-of-propagation-fiber-modes-through-lens-in-fdtd-and-zemax\/"},"modified":"2025-05-31T13:09:37","modified_gmt":"2025-05-31T13:09:37","slug":"simulation-of-propagation-fiber-modes-through-lens-in-fdtd-and-zemax","status":"publish","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/simulation-of-propagation-fiber-modes-through-lens-in-fdtd-and-zemax\/","title":{"rendered":"Simulation of propagation fiber modes through lens in FDTD and Zemax"},"content":{"rendered":"<p>&lt;p&gt;Hello everyone, I have a question related to simulations In FDTD and Zemax. Firstly, I did simulations of propagation fiber mode through 1 mm length and 200 um thickness lens. And according to examples I exported fiber mode from FDE solver as a source in zemax and used POP and it worked&nbsp;pretty well.&lt;\/p&gt;&lt;p&gt;<img decoding=\"async\" src=\"https:\/\/innovationspace.ansys.com\/forum\/wp-content\/uploads\/sites\/2\/2025\/05\/31-05-2025-1748695460-mceclip0.png\" \/>&lt;\/p&gt;&lt;p&gt;For example I got parameters of lens for 4mm focus, but then i wanted to do simulations in only FDTD to get nice picture of EM wave. Of course only in 2D because the size of simulation in 3D would be too demanding for my computer. And unfortunately i got different results.&lt;\/p&gt;&lt;p&gt;<img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/innovationspace.ansys.com\/forum\/wp-content\/uploads\/sites\/2\/2025\/05\/31-05-2025-1748696061-mceclip1.jpg\" width=\"712\" height=\"434\" \/>&lt;\/p&gt;&lt;p&gt;End of the lens is at 0 on x axis. As you can see simulated focus is closer to 1mm than 4 mm. As a BC i used stretched coordinate PML to avoid any reflections. I did mesh override close to the core of fiber and used mesh size is 0.1&nbsp; in x and 0.4 in y directions. Do you have any idea why the results are different, or is it because FDTD is more accurate here? I already tried most of the things suggested in knowledge base, but nothing changed the results in FDTD.&lt;\/p&gt;<\/p>\n","protected":false},"template":"","class_list":["post-433022","topic","type-topic","status-publish","hentry","topic-tag-LumericalFDTD-1","topic-tag-physical-optics-propagation","topic-tag-zemax-interoperability-1"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_forum_id":["27833"],"_bbp_topic_id":["433022"],"_bbp_subscription":["486113","50911"],"_bbp_author_ip":["85.222.46.216"],"_bbp_last_reply_id":["433472"],"_bbp_last_active_id":["433472"],"_bbp_last_active_time":["2025-06-06 08:05:17"],"_bbp_reply_count":["3"],"_bbp_reply_count_hidden":["0"],"_bbp_voice_count":["2"],"_bbp_engagement":["486113","50911"],"_btv_view_count":["222"],"_bbp_topic_status":["unanswered"],"_bbp_likes_count":["0"]},"test":"01159423pw-edu-pl"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/433022","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics"}],"about":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/types\/topic"}],"version-history":[{"count":0,"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/433022\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=433022"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}