leased line modems over fiber, possible?

I've got old Motorolora Codex 2550, 4 wire leased line modems.  They work great when the line is up, but the local telco screws up the line all the time (this is Nicaragua, btw).  A cable provider/isp now has fiber running from our location to our remote antenna location.  What woudl be necesarry to make these old modems run over fiber.  I figure some sort of fiber mux?  Changing the modems to another technology is not feasable, these are VISA modems and they take an eternity to change things, especially in Latin America.  What kind of money am I looking at to make this work?  thanks,
fmedinaAsked:
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asarluhiCommented:
Yes - I was, in fact, assuming that the cable company/ISP was providing strands of dark fiber.

If, in fact, the connection is IP-based, then the options are somewhat limited for keeping the old modems.  There honestly aren't a whole lot of products that I know of that encapsulate analog leased lines into an IP stream (nor could I imagine much of a demand for them!!).  There are some products to transport a full T1 over IP (see http://www.engagecom.com/html/iptube.html) - so the channel bank advice from above would apply.  

To recap, though, each side would have a channel bank that took in the 4-wire circuit (...and 23 of its closest friends, if required) and produced a framed T1.  This T1 would be transported via the product described above - which would encapsulate the T1 frames into IP, which would be transmitted via your ISP to your remote site for de-encapsulation and subsequent demultiplexing.  

It still seems kind of odd to spend weeks of tweaking time and north of $10K US to preserve modems that cost $300 when they were new ten years ago.  I guess I've seen stranger, though.

Either way, though-
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asarluhiCommented:
It would be possible to put in some kind of channel bank that multiplexed the 4 wire connection out of the modems into some sort of higher order framing (probably T-1) - which, in turn, could be sent via fiber.  This is, essentially, what the telco is doing for you right now.  

Black box (www.blackbox.com) has channel banks - the approximate cost (US$) would be somewhere around ~2k per side for the channel banks themselves, plus another $1500 per side to convert the T-1 signal into fiber.  

I would reconsider the modem-replacement question.  You can get fiber optic line drivers that present async interfaces (...exactly like your modems) at each side for a few hundred total.  This wouldn't require any reconfiguration of the terminal equipment - and would probably be the easiest/cheapest to accomplish in the long run.  

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The--CaptainCommented:
Dark fibre?  Or did the isp already light it up with some of their own equipment?  I think the above advice is presuming dark fibre.

-Jon

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The--CaptainCommented:
I've seen stuff that would do what he wants - it called an FR or ATM mux - and yes, it's quite costly.  Should work, as long as he can get his provider to give him a PVC (and feels like wasting tons of cash on legacy tech).

You're right, tho - extremely tedious to do if all you can get is an IP stream.

-Jon
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HDWILKINSCommented:
May I ask that you do one of three things.

1.  If you still have a problem let us know and give us some more details.  

2.  If you feel someone helped you, accept their answer.  If you feel that more than one person helped you, then you can split the answer.

3.  If you feel that you were not helped, then you can post a 0 point question in Community Support and ask that this be deleted.  It also be polite to advise us why its being deleted.

If we don't hear from you in a reasonable period of time, I will request that an EE Moderator

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POINTS TO ASARTUHI

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DanRollinsCommented:
Upon review of the comments here, I am recommending this disposition:

        points to asarluhi

Please post a comment if you disagree.

DanRollins -- EE database cleanup volunteer
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SpideyModCommented:
per recommendation.

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