It's not ableism. Autism doesn't give license to act in a way that makes coworkers uncomfortable. I guess I could use more careful language comrade but I'm sorry, I'm not gonna sanction acting like a creep because you're autistic. Either ask someone out or find a dating pool where pining and stuff like that is acceptable. It's not work and it's not your org. Be professional.

I'll say tho, sorry for the "Be normal" - I recognize that normalcy is contingent, but in the workplace being normal is about respect to your fellow worker. If you build up this relationship for months in your mind, the denouement is likely going to be toxic. While there's places that can be fine, in a workplace you're putting your coworker in a position where she/he has to decide if they want to keep seeing the person who has been carrying a torch for them every day or not. Yes there's HR to smooth things over sometimes, but I think it's still just unfair to you and the other person if you involve them in a long and twisty psychic obsession at a place they need to work at to pay rent, etc. we don't live in communism where they can just get easily reassigned.