Author Topic: Fiber optics, single mode && multimode??  (Read 7392 times)

Barek (jerm)

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Fiber optics, single mode && multimode??
« Topic Start: September 30, 2011, 06:38:04 PM »
I've been talking with a number of vendors about installing fiber in our manufacturing building.  We've settled on a solution that calls for 1 MDF and 6 IDF cabinets, each with ethernet switches, but with a fiber backbone.

One vendor wants to do 6 strands of singlemode and 6 strands of OM4 multimode to each cabinet.  Their pitch is that having both varieties in there gives me more flexibility and more options down the road with regard to equipment.

I'm not certain though - it almost seems that I'll end up using one and the other will just sit dark.

Anyone have any experience with this kind of thing?
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egamma

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Re: Fiber optics, single mode && multimode??
« Reply #1: September 30, 2011, 07:11:36 PM »
I recommend multimode. I used to work with fiber on a university campus, and almost all of our fiber was multimode. Singlemode is mostly useful when you need extremely long distances, and unless your building is Boeing's manufacturing plant, you won't need to worry about that.

From wikipedia:
The equipment used for communications over multi-mode optical fiber is less expensive than that for single-mode optical fiber.[1] Typical transmission speed and distance limits are 100 Mbit/s for distances up to 2 km (100BASE-FX), 1 Gbit/s to 220–550 m (1000BASE-SX), and 10 Gbit/s to 300 m (10GBASE-SR).

Equipment for single mode fiber is more expensive than equipment for multi-mode optical fiber, but the single mode fiber itself is usually cheaper in bulk. In 2005, data rates of up to 10 gigabits per second were possible at distances of over 80 km (50 mi) with commercially available transceivers (Xenpak). By using optical amplifiers and dispersion-compensating devices, state-of-the-art DWDM optical systems can span thousands of kilometers at 10 Gbit/s, and several hundred kilometers at 40 Gbit/s.

Barek (jerm)

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Re: Fiber optics, single mode && multimode??
« Reply #2: September 30, 2011, 07:17:36 PM »
Thanks egamma.

Our manufacturing building is 1,650 feet long.  I know single mode is great for very long hauls.  OM4 multimode is good for 1,500, which is sufficient, in this case that last 150 feet can be covered by ethernet.

The more I look at this, the more I think that we can ditch the single mode and go all multimode.
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egamma

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Re: Fiber optics, single mode && multimode??
« Reply #3: September 30, 2011, 07:50:34 PM »
Thanks egamma.

Our manufacturing building is 1,650 feet long.  I know single mode is great for very long hauls.  OM4 multimode is good for 1,500, which is sufficient, in this case that last 150 feet can be covered by ethernet.

The more I look at this, the more I think that we can ditch the single mode and go all multimode.

Make them provide a concrete use example for the SM, other than increasing their profit. I can't see one.

Barek (jerm)

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Re: Fiber optics, single mode && multimode??
« Reply #4: September 30, 2011, 09:31:46 PM »
Yup yup.  ditched single mode.

Followup question:  6 strands to each cabinet, or 12?   There'll be at least one switch in each cabinet, in some cases more, but multiple switches will likely use stacking.  12 strands means lots of dark fiber.  But is having that extra worth the cost, I wonder..
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egamma

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Re: Fiber optics, single mode && multimode??
« Reply #5: October 01, 2011, 09:02:57 PM »
Yup yup.  ditched single mode.

Followup question:  6 strands to each cabinet, or 12?   There'll be at least one switch in each cabinet, in some cases more, but multiple switches will likely use stacking.  12 strands means lots of dark fiber.  But is having that extra worth the cost, I wonder..

Are all 6 cabinets are direct-run from your MDF? I would just do 6. Even if you have massive bandwidth needs, you should have plenty of bandwidth with 3 pairs.

I dont know if you have massive bandwidth needs, but you should be fine with 6.

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Re: Fiber optics, single mode && multimode??
« Reply #6: October 05, 2011, 06:18:23 PM »
Are all 6 cabinets are direct-run from your MDF? I would just do 6. Even if you have massive bandwidth needs, you should have plenty of bandwidth with 3 pairs.

I dont know if you have massive bandwidth needs, but you should be fine with 6.

Well, if the bandwidth needs are large (probably nearing 450 G/s?), 6 may not be enough redundancy in the event of a failure, in which case the 12 will provide you with full redundancy. It isn't always just about bandwidth.
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egamma

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Re: Fiber optics, single mode && multimode??
« Reply #7: October 05, 2011, 08:08:53 PM »
Well, if the bandwidth needs are large (probably nearing 450 G/s?), 6 may not be enough redundancy in the event of a failure, in which case the 12 will provide you with full redundancy. It isn't always just about bandwidth.

If they're that large then I expect he would have someone on his staff answering questions instead of me  :o

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Re: Fiber optics, single mode && multimode??
« Reply #8: October 05, 2011, 09:18:40 PM »
If they're that large then I expect he would have someone on his staff answering questions instead of me  :o

Maybe he's that person on the staff. ;)
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egamma

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Re: Fiber optics, single mode && multimode??
« Reply #9: October 06, 2011, 01:10:18 AM »
Maybe he's that person on the staff. ;)

True. all my assumptions have been that he is using the system for regular internet/office use, not massive data transfers. I know it says manufacturing facility, but don't they normally store all needed code locally on the die press or whatever?

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Re: Fiber optics, single mode && multimode??
« Reply #10: October 06, 2011, 03:29:03 AM »
True. all my assumptions have been that he is using the system for regular internet/office use, not massive data transfers. I know it says manufacturing facility, but don't they normally store all needed code locally on the die press or whatever?

No, firstly depending on what sort of process, the information from various machines and sensors will be needed in several other processes, requiring some sort of communication system. Secondly nearly all manufacturing systems now have MES, asset management and other data analysis directly communicating to the process machines to extract all that lovely data that makes all those lovely graphs for management, things like resources in, resources out, down time, fault logs etc. For many years these needs were served by propriety communication protocols often based on RS-232 RS-485 RS422 etc, but since Ethernet and fibre are now so cheap an affordable, and as the amount of data utilised in processes has increased, they have moved to these in a lot of cases.
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egamma

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Re: Fiber optics, single mode && multimode??
« Reply #11: October 06, 2011, 05:24:17 AM »
No, firstly depending on what sort of process, the information from various machines and sensors will be needed in several other processes, requiring some sort of communication system. Secondly nearly all manufacturing systems now have MES, asset management and other data analysis directly communicating to the process machines to extract all that lovely data that makes all those lovely graphs for management, things like resources in, resources out, down time, fault logs etc. For many years these needs were served by propriety communication protocols often based on RS-232 RS-485 RS422 etc, but since Ethernet and fibre are now so cheap an affordable, and as the amount of data utilised in processes has increased, they have moved to these in a lot of cases.

And if he had such a system, he would likely know what his precise requirements are, or the people doing the installations would know. They seem to be leaving it up to him, which indicates to me that the fiber needs are likely minimal.

If 12 fibers is only a little more expensive than 6--and you could get away with only terminating half of them--then you might as well run 12. But I'm trying to spend as little money as possible.

De-Legro

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Re: Fiber optics, single mode && multimode??
« Reply #12: October 06, 2011, 05:30:42 AM »
And if he had such a system, he would likely know what his precise requirements are, or the people doing the installations would know. They seem to be leaving it up to him, which indicates to me that the fiber needs are likely minimal.

If 12 fibers is only a little more expensive than 6--and you could get away with only terminating half of them--then you might as well run 12. But I'm trying to spend as little money as possible.

You would be surprised. I'm a control engineer, my networking knowledge is limited to what I have learnt while installing control systems, yet I've been asked to design large scale fibre networks, the logic being that since the network would connect my control architecture together, obviously I would know what is required. It is similar in IT, managers just assume that computer people know all this stuff. It is amazing on large scale projects how much money can be wasted because for some reason nobody thinks to actually engage a specialist in different required disciplines.
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cjnodell

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Re: Fiber optics, single mode && multimode??
« Reply #13: October 06, 2011, 08:27:46 PM »
The problem is that a lot of information is needed when determining how much fibre to run. What is the anticipated load? What are your plans for redundancy? What equipment are you using? What expansion plans do you have? What is the budget like? How many clients are there now and how many will there be next year?

For example, if you are trying to get away with old switches using a bunch of 1gig ports in a port group you will need more fibre than a newer switch with a single ten gig uplink. If redundancy is too expensive and not intended to be implemented in the future (bad idea in my mind) then you just cut the needed runs in half. If you do plan on having redundancy and can tolerate half the bandwidth during an outage and are OK with using both links when possible you can also reduce the number of runs. Otherwise more runs are needed. So many variables!

Barek (jerm)

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Re: Fiber optics, single mode && multimode??
« Reply #14: October 07, 2011, 11:32:31 PM »
Yeah, I'm it as far as technical staff goes, and I have pretty minimal experience thusfar with fiber, hence the question.

The purpose of this fiber network is just to make data connectivity available throughout the manufacturing building.  I don't expect to be moving large volumes of traffic, aside maybe from data from IP cameras.  Even then, I don't expect to fill up a 1 gig pipe with that traffic.  The rest of it will be for PLC/machine tools, some workstations and IP phones, maybe a few access points, but the traffic needs (aside from the IP cameras) should be quite small.

In fact, this fiber plan should give me throughput of up to 10Gbps, while my switching equipment will likely only handle 1Gbps connectors.  But having that extra potential bandwidth on the fiber gives me growth for the future.

I appreciate all of the answers and insight.
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