presumably you can have more than one laser link using the same frequency and bandwidth of light since it is a laser beam just put the next link a couple meters over and they should not interfere with each other at all.
The parent comment is confused. NYC mesh doesn't use actual laser beams, they use a cheap 5Ghz TDMA solution made by Ubiquiti called Litebeam. Interference can be a big issue for this equipment, especially in an urban environment with a high noise floor.
(No affiliation with NYC folks, just a WISP guy handing out the basics)
(No affiliation with NYC folks, just a WISP guy handing out the basics)