First the bad news; as a fiber network engineer for the last 20 years and a technician for 10 before that, hearing these comments and answers is painful, and a bit frustrating.
This should be a clue that either a lot more research and investigation needs to be done, or hire someone to do it that knows what is going on. This is assuming the network you are talking about campus LAN or bigger. Anything smaller and the installation cost to do anything with fiber will always outweigh the overall benefit with regards to both performance or budget.
Someone mentioned DWDM? DWDM is strictly carrier class, long haul, single-mode fiber (and a very specific type of single-mode fiber at that), and more complicated than newcomers will conceive of, before thinking your gonna whip up this DWDM network. I highly doubt the network in which this person is asking advice about comes close the required performance of DWDM equipment (and correct fiber specs), I say that because if it was, he would never need to ask any of these questions and would rather be already very knowledgeable about fiber.
It is truly an instance where it is almost necessary that you know as much about installing the fiber, splicing it, terminating it, and testing it, as the vendor you will hire to do this work. The install, configuration, and turn up of the equipment isn't even practical to get involved with to deep, it takes years of experience installing and troubleshooting these systems to do it right, and right the first time. and if you really want to install some fiber or build your fiber network as you said, you can do this yourself with not a fraction of the fiber knowledge needed for wan, metro, long haul, and sub-oceanic systems. there really isn't a lot of trouble you can get into. Install a 6 or 12 strand single-mode fiber optic cable between every switch, hub and router in your network. direct terminate sc connectors or splice sc pigtails to each fiber strand in a mounted fiber panel and test. this work you will need to hire a vendor for. You design, purchase and install new switches or other equipment your replacing, and turn up the new service all yourself very, very, easily. 6-12 strand fiber cables are very easy and usually done very well (ie., the polish, the quality of test results, etc). not a lot of babysitting of fiber technicians to make absolutely sure they are installing the correct equipment at the this level is what I'm getting at.
It's not like your doing a live mid-sheath splice on a 120 strand fiber cable working off a detailed splice schematic put together well before your planned event network outage, counting on it being created and printed correctly. these are typical tasks on systems requiring anything like DWDM or larger networks. anyway best of luck and take my advice, my take on it here wont differ much between anyone that really knows what they're doing with fiber.
I've worked on every phase of just about the most technically advanced fiber networks that are in service today; as well as design from small campus LAN to extended long haul networks covering the united states and sub-oceanic systems. To some it up in one sentence I would say if it is a small network in physical size (single building or one level), short distances between switches and hubs, and satisfactory reports from end users with regards to speed, then don't worry about fiber; stick with copper and wireless and put the money somewhere else. like network documentation software, and maps where it will help tremendously during future localized network outages!!
If its that larger metro or campus network, then just hire someone to do the fiber. your only job here is to get that deeper knowledge of fiber and manage the vendors. Once again, its only in the case your network is reasonably small, along with the stubborn idea that you absolutely must have fiber for the this small network that I tell you just go ahead its safe to do it yourself.