[vcf-midatlantic] SX GBIC fiber cable speed

Jameel Akari jakari at bithose.com
Mon Feb 15 20:06:23 UTC 2021

On 2021-02-15 14:38, Ethan O'Toole wrote:
> FS.COM is pretty good.

I'm hard-pressed to think of anyone else that provides the same kind of 

> I used to work at a place that used 10baseFL. It was a big waste of
> money. Every computer that came in had an Intel 100mbps nic, it got
> yanked and replaced with a $400 10 megabit fiber card. But when
> lightning struck near one of the buildings, it blew out like $100K
> worth of Lucent Definity phone boards and every HP cat5 jetdirect
> board.

We had it to span a 12-story building with waaaaay to large a collision 
domain. :)
But it sounds like 10base-FL (forgot that name...) saved your computers?

> I still have a Sun and Indigio2 FDDI card or two somewhere, and one
> for Indy. At one point in time I had like 5 Indy/Challenge S all on
> FDDI. Will probably bring some of it to the next swap event.

I have some mild interest in these things. :)


> On Mon, 15 Feb 2021, Jameel Akari via vcf-midatlantic wrote:
>> Before somebody says "it's not vintage!" consider that 1Gb Ethernet on 
>> fiber was spec'd for FDDI cables, and there were optical transceivers 
>> for even 10Mb Ethernet - I brought a set of AUI to 2xST for the Unix 
>> Town networking, just because I had them. Also, early 1Gb Ethernet was 
>> all 1000base-SX with SC connectors, at least that I saw.  It took a 
>> while for copper UTP to be supported.  I have a few Digital and Sun 
>> 1Gb NICs that are optical, and so I run them that way.
>> Now, at 25m, you /really/ don't need fiber for 1Gb Ethernet.  Properly 
>> installed UTP copper should work reliably for years in normal 
>> environments. It's surprising and unusual you had some fail.  
>> Exception: crimped RJ45 ends on solid conductor UTP cable is likely to 
>> fail over time if there's any movement or vibration.  Punch on some 
>> jacks and use premade jumpers.
>> You can run 10Gb over Cat6A UTP at this distance as well.  This is 
>> harder to terminate by hand, but you could just get premade patch 
>> cables (they will be 26-28 AWG stranded, most likely)
>> But since you've already got optics and fiber is a lot cheaper than it 
>> used to be... why not?
>> - You're better off not trying to use the same cabling for 1Gb and 
>> 10Gb, but:
>> - You *can* do short-range 1000base-SX with OM3, though it's not spec 
>> depending on where you look.  It will work.
>> - By the book, use OM2 for 1Gb and OM3 for 10Gb, assuming short-range 
>> optics like your SX SFPs. (SFP, not GBIC, if you're talking LC 
>> connectors)
>> - OM2 is usually orange and OM3 is usually aqua-blue.
>> - As far as I can tell, you don't need mode conditioning for SX 
>> (short-range) optics.  If you needed to use LR 1Gb optics, or use 
>> single-mode optics into MMF cabling plant, then you'd use a 
>> mode-conditioning cable to clean up the noise.
>> - Bend radius is typically 10x the outside diameter of the cable, 
>> unless otherwise specified. Here, it's a single strand of a duplex 
>> cable.  So if it's about 3mm across, bend radius is 30mm.  (but see 
>> below on bend-insensitive cable). When I dress cables I usually 
>> eyeball 3-4" diameter loops.  Any smaller just doesn't look or feel 
>> right anyway.
>> I'm assuming that at only 25m you're buying pre-terminated cables with 
>> LC plugs both ends. This means you need large enough holes in things 
>> for those plugs to fit through.  Otherwise it's definitely not worth 
>> splicing your own at this scale.
>> https://www.fs.com/products/74386.html?attribute=226&id=99219 - for 
>> $16.72 each at 25m, you get new "bend insensitive" cable (7.5mm 
>> radius!)
>> I love FS.com for all manner of fiber and related cabling:
>> https://community.fs.com/blog/advantages-and-disadvantages-of-multimode-fiber.html
>> https://community.fs.com/blog/single-mode-cabling-cost-vs-multimode-cabling-cost.html
>> These have some rule-of-thumb charts.
>> I think that covers it?
>> -- Jameel Akari
>> On 2021-02-15 12:25, Neil Cherry via vcf-midatlantic wrote:
>>>  I've posted this in the CDL list also. I don't know of a polite way 
>>> to
>>>  post once to both and
>>>  I'm not sure it's a good idea to try. :-)
>>>  It has been a while since I played with fiber (2010) and I'm trying 
>>> to
>>>  figure out if I
>>>  should go fiber or copper in my home. Here's what I know from my 
>>> current
>>>  switch:
>>>  - SX GBIC
>>>  - LC
>>>  - duplex
>>>  - MMF
>>>  I want to buy about 25M of fiber. I think the price is competitive
>>>  with copper. I'm also
>>>  hoping that the fiber will age better than the copper. I'm seeing a
>>>  few old copper drops
>>>  fail to lower settings. One went to 10/half (wow, that's bad).
>>>  The GBIC & switch I have handle 1G. So I can easily pop in a few
>>>  1000baseT, put them
>>>  into a LAG and get 4G (4 ports). So I'm covered for a while.
>>>  - Can the same piece of fiber handle 1G or 10G? (in case I upgrade 
>>> in
>>>  the future).
>>>  - Does anyone know the bend radius of this fiber?
>>>  - What color should I expect for SX fiber. ?
>>>  - What's a "mode-conditioning patch cord" ?
>>>  I'm seeing a $35 price for 25 Meter OM3 LC LC Fiber Patch Cable
>>>  (Corning 50/125um core/cladding)
>>>  and it says 1G but with a "mode-conditioning patch cord" (an 
>>> attenuator?).
>>>  Any pointers?

Jameel Akari

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