Due to the vagaries of telecom pricing, I've ended up with a 2.5gig wavelength service between two locations when what I really wanted was a gig-e or two.

I'm really not sure if this is a "transparent" wave service or not... the carrier is using gear from Ciena to hand it off to us and they seem to be big on transparent waves, so maybe it is, but nobody seems to be able to say for sure.

OTU-1 ? Is it coming off a ciena CN 4200 ? OTN / G.709 ? Go see: http://www.ciena.com/products/flexselect_otn.htm or this one, (but the OTN/G.709 link seems to be failing for some reason) http://www.sonet.com/EDU/edu.htm OTU-1 can carry an intact OC-48 that is really part of someone elses network with no undesired interactions (think "tunnel"). OTU-2 carries an OC-192 the same way, and OTU-3 is for OC-768. With the right hardware, OTU-n transports random other optical (ethernet, storage, video, etc) signals without having them on an OC-x SONET signal. And Sonet traffic can also be muxed in and carried with all the random other stuff on the same OTU-n pipe. They can probably cheerily hand you either an OC-48 capable connection or an OTU-1 one to match what you are getting for hardware, but ask. Their OTU-1 based service they are providing you might be an individual wave/lambda/color but more likely is on an OTU-2 or even OTU-3 on a system that potentially carries many dozens of them on the same fiber using DWDM.. The OTN/G.709 stuff is relatively new and very desirable, Ciena has is as well and some others - see if that is what they are using. You may want to see what Ciena has to offer you to make use of it.. They can take in an OTU-n signal in what at first glance seems to be just a transponder or possible a mux-ponder card, but they are doing a complete OEO transformation and the E part, unlike some of their competition, is used effectively to let random spare ports even on other cards in the chassis be used for components being muxed up onto this particular OTU-x signal. It is quite flexible, and that could be why you are getting confusing information about what you actually have available to you. You could get old Cerent 454 aka Cisco 15454 gear pretty cheap, but the original 15454 gig-e cards will not make you happy. Newer cards can give you 2 full Gig-es and probably a modest amount of spare DS3 or DS1 tdm capacity on an OC-48, but then the price will be higher. They probably want more $$s if you ask them to hand you your "OC-48" as multiple smaller pieces (eg 2 x Gig-e), and I would think you should want to do the muxing yourself., but ask, if that is easiest for you. It will help if you KNOW what their hardware is actually capable of.

So, how can I best make use of this beast in my ethernet-centered world?

1- Since it doesn't cost me anything, I'm going to try to send a gigabit LX signal and see what happens. The handoff from the carrier to me seems to be a plain 1310 type of signal... Light goes on, light goes off, maybe the carrier's gear doesn't care that it's not modulating "fast enough" and I'll get lucky?

Unlikely. They probably have to know exactly what is coming at them, though it may be easily configured to be any of several possibilities at or around the same speed (eg OTU-1 vs OC-48)

2- MRV's EM2009-GM2 card takes 2xGE and spits out a 2.5G signal of some sort. However they won't guarantee me that it'll work when talking to the Ciana card the carrier is using. I should probably inquire about their return policy and go for it.

Don't play with "returns", have them DEMO it for you for a few weeks. If they won't, shop elsewhere. MRV has all sorts of nice "bag or tricks" gadgets, but I'd first ask Ciena what small chassis they have that can play here. It will also be a "free" education into what the carrier's own capabilities probably are, and Ciena should know what equipment is in use there.