alright... well The first thing that gets to pretty much any Fox user is the fact lasers are useless in the match up heres why:
SHDLs travel too high
SHLs need precise aim, something you should NOT be concentrating on
SHTLs Get block by pikmin
Standing lasers get blocked by pikmin
Really the only time you should laser in this match up is when olimar camps, you camp back your lasers block the pikmin majority of the time but still i would try to approach despite the fact that's what they want, unfortunately it's your only choice.
Now he ***** our already meager approach options your only legit options would be Nair, Dash attack, Illusion :\, a fastfalled Fair (one or 2 legs hit), And a riskier on would be drill. Now you may think that's a lot of options but they are ALL risky so expect to get punished.
Now What does fox have on olimar? Tilts... seriously i say this all the time cause it's true tilts destroy small characters, Why? because they almost always hit and are safe options and they lead into a fair bit of things. Up tilt is fundamental with every match up. Side tilt leads in upsmash, drill, Nair, Dash attack it's up to you to be creative. Down tilt is easily the most undrestimated Tilt learn how to space it and get the comboing sweetspot (white tip of his tail) and it's a great move it leads into any aerial.
Offstage is Fox's **** zone in this match up olimar has no edgegame, just don't get spiked be above him at all times and watch out for his UpB cause it WILL stage spike you in most cases not much to be said here, shine spike or nair.
Olimar has one start up combo most mains use it's Downthrow>Fair the second you get Dthrowed at low percents DI Away form olimar as much as you can cause this really hurts fox at lower percents.
Olimar's kill power is completely broken he can kill you at like 60 percent so play very carefully. Space well and even though i said lasers are useless i still move with SHDLs because it gets the slightest more damage than doing nothing so still use those. Just either be VERY agressive or Very defensive.
Thats all i could remember for now so i hope that helps
i would get some video's against an olimar for you bu i haven't uplaoded any of mine so sorry bout that.