I've played a couple of Olimars during Socal tournys, many of them are really good (Mr.X).
I noticed that if you stay too far away from olimar, he seems to have a huge advantage over fox. The trick to playing against olimar in my opinion would be to stay close to him at all times in order to pressure him to get some distance.
If you fight Olimar mid-range, you're almost surely going to lose since his Pikmin specialize in mid-range fighting. So your best bet would be to hug onto olimar, but be smart about it.
Fox has a really strong advantage over olimar through arial attacks. Since Olimar can only smash horizontally or strictly vertically, coming at an angle with a SH fAir or dAir can be helpful. One thing I learned is that if Olimar attempts to uSmash while fox does his dAir, almost certainly Fox's dAir wins because he cancels out the pikmin and then drills into olimar.
As far as lasering goes, don't waste your time camping an Olimar. If the Olimar is quick, he'll easily punish you for staying in your laser position for too long, and that's definately not what you would want.
There are two really easy ways to kill an Olimar: Vertical KO or edge gimping.
Of course fox specializes in killing almost any character through an uSmash at around the range of 80% to 115% (this includes all light to all heavy characters). Because Olimar is classified as a light character, you can easily Vertically KO him through an uSmash at around 90% for a sure kill.
Another KO technique that could be situational is when you edge gimp an Olimar through edge hogging while Olimar has no other options when he is off the stage. If you have olimar near the edge of the stage, you can do an easy combo of dAir > dSmash which will launch Olimar in a downward direction, a really hard recovery for olimar if you edgeguard. Just remember not to stay on the edge for too long just in case he gets smart and smacks you with a fAir =).
In order to kill Olimar, I prefer doing a dAir > uSmash combo at high percentage because it's almost always a certain kill, but don't forget you have the other option of gimping Olimar on the edge.
I think I covered everything. If not, i'm sure someone else will fill in the blanks =).
-Gamble