1000Base-SX Peer-to-peer

1000Base-SX Peer-to-peer

Post by Maarten ter Mor » Sun, 08 Jun 2003 05:19:08



Hi,

here's a message from another one of those idiots who want to have a Gigabit
Ethernet link and only connect two machines to it. And not even over copper
this time, but over fiber too!

What I plan to do is connect device A (an embedded appliance) to my
workstation, B. Device A is equipped with a 1000Base-SX GigE interface. Now,
from what I gather, this physical medium consists of two fibers, one for
send and one for receive, with SC connectors at the ends.
Can I simply cross the fibers like in an old null modem cable?  So send on
machine A to receive on machine B and vice versa?

I know I should get a switch and I probably will - but suppose the boss cuts
my budget, _can_ I use this kind of cross-connection?

Thanks.

Maarten ter Mors

 
 
 

1000Base-SX Peer-to-peer

Post by William Tass » Sun, 08 Jun 2003 05:41:22



> Hi,

Hello

Quote:> here's a message from another one of those idiots who want to have a
> Gigabit Ethernet link and only connect two machines to it. And not
> even over copper this time, but over fiber too!

takes all sorts

Quote:> What I plan to do is connect device A (an embedded appliance) to my
> workstation, B. Device A is equipped with a 1000Base-SX GigE
> interface. Now, from what I gather, this physical medium consists of
> two fibers, one for send and one for receive, with SC connectors at
> the ends. Can I simply cross the fibers like in an old null modem
> cable?  So send on machine A to receive on machine B and vice versa?

that's it.  if you get one of those patch leads that has send and receive
moulded together you should find that this is the only option you have

Quote:> I know I should get a switch and I probably will - but suppose the
> boss cuts my budget, _can_ I use this kind of cross-connection?

No need for a switch with just two devices

--
William Tasso - http://www.WilliamTasso.com

 
 
 

1000Base-SX Peer-to-peer

Post by Daniel J McDona » Wed, 11 Jun 2003 06:03:27




Quote:>What I plan to do is connect device A (an embedded appliance) to my
>workstation, B. Device A is equipped with a 1000Base-SX GigE interface. Now,
>from what I gather, this physical medium consists of two fibers, one for
>send and one for receive, with SC connectors at the ends.
>Can I simply cross the fibers like in an old null modem cable?
Absolutely
>  So send on
>machine A to receive on machine B and vice versa?

Light to dark and dark to light (don't look at the light, but in a
darkened room you should be able to see a red spot if you point it at a
white piece of paper).

--
Daniel J McDonald CCIE # 2495, CNX
Visit my website: http://www.austinnetworkdesign.com

 
 
 

1000Base-SX Peer-to-peer

Post by M.C. van den Bovenkam » Wed, 11 Jun 2003 07:21:59



> Light to dark and dark to light (don't look at the light, but in a
> darkened room you should be able to see a red spot if you point it at a
> white piece of paper).

Are you sure that works?

AFAIK, visible red ends somewhere around 750 nm in humans; anything
longer is IR. And with -SX wavelength defined as falling between 770 and
860 nm (and mostly at the long end of that range, as '850 nm'), I'd say
you're unlikely to see anything.

I know I never have.

                Regards,

                        Marco.

 
 
 

1000Base-SX Peer-to-peer

Post by Ben Hockenhul » Wed, 11 Jun 2003 12:16:19





>> Light to dark and dark to light (don't look at the light, but in a
>> darkened room you should be able to see a red spot if you point it at a
>> white piece of paper).

> Are you sure that works?

> AFAIK, visible red ends somewhere around 750 nm in humans; anything
> longer is IR. And with -SX wavelength defined as falling between 770 and
> 860 nm (and mostly at the long end of that range, as '850 nm'), I'd say
> you're unlikely to see anything.

Yep, I've seen red light on cisco-branded (and manufactured by a variety
of manufacturers) SX GBICs many time.  I suppose it could just be light
for convenience's sake, and not actually at carrier wavelength, but it's
there nonetheless.

Ben

 
 
 

1000Base-SX Peer-to-peer

Post by Glen Herrmannsfeld » Wed, 11 Jun 2003 13:56:45





> > Light to dark and dark to light (don't look at the light, but in a
> > darkened room you should be able to see a red spot if you point it at a
> > white piece of paper).

> Are you sure that works?

> AFAIK, visible red ends somewhere around 750 nm in humans; anything
> longer is IR. And with -SX wavelength defined as falling between 770 and
> 860 nm (and mostly at the long end of that range, as '850 nm'), I'd say
> you're unlikely to see anything.

With enough power you can see 850nm.

http://an.hitchcock.org/repairfaq/sam/laserioi.htm#ioicav2

The eye sensitivity is pretty much an exponential tail, about a factor of
two for each 10nm down.  It 850nm you might see it just before your eye
melts, but at 770nm, in a dark enough room you should be able to see it.

-- glen

 
 
 

1000Base-SX Peer-to-peer

Post by M.C. van den Bovenkam » Wed, 11 Jun 2003 16:31:59



> With enough power you can see 850nm.

> http://an.hitchcock.org/repairfaq/sam/laserioi.htm#ioicav2

> The eye sensitivity is pretty much an exponential tail, about a factor of
> two for each 10nm down.  It 850nm you might see it just before your eye
> melts, but at 770nm, in a dark enough room you should be able to see it.

Makes sense. I don't think I ever took the trouble to switch off the
lights in the equipment room :-).

                Regards,

                        Marco.

 
 
 

1000Base-SX Peer-to-peer

Post by Phil Partridg » Thu, 12 Jun 2003 06:01:26







>> > Light to dark and dark to light (don't look at the light, but in a
>> > darkened room you should be able to see a red spot if you point it at a
>> > white piece of paper).

>> Are you sure that works?

>> AFAIK, visible red ends somewhere around 750 nm in humans; anything
>> longer is IR. And with -SX wavelength defined as falling between 770 and
>> 860 nm (and mostly at the long end of that range, as '850 nm'), I'd say
>> you're unlikely to see anything.

>With enough power you can see 850nm.

>http://an.hitchcock.org/repairfaq/sam/laserioi.htm#ioicav2

>The eye sensitivity is pretty much an exponential tail, about a factor of
>two for each 10nm down.  It 850nm you might see it just before your eye
>melts, but at 770nm, in a dark enough room you should be able to see it.

>-- glen

With the caveat (as original poster did not seem to be too familiar with
fibre...) NEVER look directly at the end of a fibre. - Even if you
*know* there is no signal on it. If you never do it, you will never wish
you hadn't!

A darkened room and point it at a sheet of paper, or use a visible
wavelength source to id which fibre is which.
--
Phil Partridge

 
 
 

1. 1000Base-SX Peer-to-peer

Hi,

here's a message from another one of those idiots who want to have a Gigabit
Ethernet link and only connect two machines to it. And not even over copper
this time, but over fiber too!

What I plan to do is connect device A (an embedded appliance) to my
workstation, B. Device A is equipped with a 1000Base-SX GigE interface. Now,
from what I gather, this physical medium consists of two fibers, one for
send and one for receive, with SC connectors at the ends.
Can I simply cross the fibers like in an old null modem cable?  So send on
machine A to receive on machine B and vice versa?

I know I should get a switch and I probably will - but suppose the boss cuts
my budget, _can_ I use this kind of cross-connection?

Thanks.

Maarten ter Mors

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