Designing UIs has been part of my job for a while now, and it's always about the bigger picture. Where is this "optional" information being used? If it's optional, does this introduce complexity down the line (handling / not handling it depending on whether it was provided)?
You can always break down and simplify things. Perhaps this optional information is irrelevant -- exclude it altogether. Is it relevant in some contexts only? Handle it separately for these contexts only.
Marking "required" fields is lazy design imo.