On 08/09/2010 22:32, Felix Nkansah wrote:
> Is there a way to set the transceiver interface on the 7600 to adjust to the
> short distance? such as changing the transmission power or something?
>
> Your suggestions please. Thanks.

Put an optical attenuator on the link. This will cost you a very small
amount of money (couple of €/$). You should be able to get them from the
same place where you buy your fibre cables.

Nick
_______________________________________________
cisco-nsp mailing list cisco-...@puck.nether.net
https://puck.nether.net/mailman/listinfo/cisco-nsp
archive at http://puck.nether.net/pipermail/cisco-nsp/

On Wed, 8 Sep 2010, Felix Nkansah wrote:

> I am told that using the LR for short distance connections would cause
> problems, but we don't have time to order new transceivers.

10GBASE-LR is for 1m - 10km distances. We routinely put 1m patch cords on
LRs and it's just fine.

10GBASE-ER/ZR is for 40 and 80km respectivel need attenuators, I'd
recommend at least 5, preferrably 10dB minimum attenuation.

> Is there a way to set the transceiver interface on the 7600 to adjust to the
> short distance? such as changing the transmission power or something?

No such thing, go with the external optical attenuators recommended by a
previous poster.

--
Mikael Abrahamsson email: swm...@swm.pp.se
_______________________________________________
cisco-nsp mailing list cisco-...@puck.nether.net
https://puck.nether.net/mailman/listinfo/cisco-nsp
archive at http://puck.nether.net/pipermail/cisco-nsp/

On Thu, Sep 9, 2010 at 07:55, Mikael Abrahamsson <swm...@swm.pp.se> wrote:

> On Wed, 8 Sep 2010, Felix Nkansah wrote:
>
> I am told that using the LR for short distance connections would cause
>> problems, but we don't have time to order new transceivers.
>>
>
> 10GBASE-LR is for 1m - 10km distances. We routinely put 1m patch cords on
> LRs and it's just fine.
>
> 10GBASE-ER/ZR is for 40 and 80km respectivel need attenuators, I'd
> recommend at least 5, preferrably 10dB minimum attenuation.<swm...@swm.pp.se>

He should actually be ok even with ER and no attenuators as minimum transmit
power is -4.7 dBm and max receive power is -1 dBm (per cisco site).
Just check optical power levels and see if they are in limits.
_______________________________________________
cisco-nsp mailing list cisco-...@puck.nether.net
https://puck.nether.net/mailman/listinfo/cisco-nsp
archive at http://puck.nether.net/pipermail/cisco-nsp/

On Thu, 9 Sep 2010, Danijel wrote:

> He should actually be ok even with ER and no attenuators as minimum
> transmit power is -4.7 dBm and max receive power is -1 dBm (per cisco
> site). Just check optical power levels and see if they are in limits.

Well, the maximum allowable transmit power is +4 dBm so that's definitely
blinding on a -1 dBm maximum receiver.

So unless one always checks each individual unit before trying it (think
future spare replacements etc) it's better to go with worst combination of
min/max values and then a 5 dB attenuator is a must.

--
Mikael Abrahamsson email: swm...@swm.pp.se
_______________________________________________
cisco-nsp mailing list cisco-...@puck.nether.net
https://puck.nether.net/mailman/listinfo/cisco-nsp
archive at http://puck.nether.net/pipermail/cisco-nsp/

On Thu, 9 Sep 2010 09:12:37 +0200, you wrote:

> He should actually be ok even with ER and no attenuators as minimum
> transmit power is -4.7 dBm and max receive power is -1 dBm (per cisco
> site). Just check optical power levels and see if they are in limits.

Uhm, no.

*Maximum* transmit power is 4 dBm and max receive is -1 dBm, so an
attenuator is certainly highly recommended for short distances.

-A

_______________________________________________
cisco-nsp mailing list cisco-...@puck.nether.net
https://puck.nether.net/mailman/listinfo/cisco-nsp
archive at http://puck.nether.net/pipermail/cisco-nsp/

On Thu, Sep 9, 2010 at 09:59, Asbjorn Hojmark - Lists <li...@hojmark.org>wrote:

> On Thu, 9 Sep 2010 09:12:37 +0200, you wrote:
>
> > He should actually be ok even with ER and no attenuators as minimum
> > transmit power is -4.7 dBm and max receive power is -1 dBm (per cisco
> > site). Just check optical power levels and see if they are in limits.
>
> Uhm, no.
>
> *Maximum* transmit power is 4 dBm and max receive is -1 dBm, so an
> attenuator is certainly highly recommended for short distances.
>

Yes, but it won't be transmitting max power for sure. All I'm saying that it
will work even without attenuators.
He can always check power levels and see if there is a need for an
attenuator.
_______________________________________________
cisco-nsp mailing list cisco-...@puck.nether.net
https://puck.nether.net/mailman/listinfo/cisco-nsp
archive at http://puck.nether.net/pipermail/cisco-nsp/

On Thu, 9 Sep 2010 10:02:46 +0200, you wrote:

>> *Maximum* transmit power is 4 dBm and max receive is -1 dBm, so an
>> attenuator is certainly highly recommended for short distances.

> Yes, but it won't be transmitting max power for sure.

No... it might be transmitting with only 2, or even 0 dBm, but that's
still too much.

> All I'm saying that it will work even without attenuators.

Yeah, you're likely to get a link. That's certainly not the same thing
as it being a recommended setup for production.

> He can always check power levels and see if there is a need for an
> attenuator.

You are aware that the power levels can and do change?

The attenuator might be 1$, so why bother trying to run something out
of spec?

-A

_______________________________________________
cisco-nsp mailing list cisco-...@puck.nether.net
https://puck.nether.net/mailman/listinfo/cisco-nsp
archive at http://puck.nether.net/pipermail/cisco-nsp/

>> He should actually be ok even with ER and no attenuators as minimum
>> transmit power is -4.7 dBm and max receive power is -1 dBm (per cisco
>> site). Just check optical power levels and see if they are in limits.

>Uhm, no.

>*Maximum* transmit power is 4 dBm and max receive is -1 dBm, so an attenuator is certainly highly recommended for short distances.

"Minimum cabling distance for -LR, -SR, -LX4, -ER modules is 2m, according to the IEEE 802.3ae standard"
http://www.cisco.com/en/US/prod/collateral/modu...

/chris

_______________________________________________
cisco-nsp mailing list cisco-...@puck.nether.net
https://puck.nether.net/mailman/listinfo/cisco-nsp
archive at http://puck.nether.net/pipermail/cisco-nsp/

On Thu, 9 Sep 2010 10:46:29 -0500, you wrote:

>> *Maximum* transmit power is 4 dBm and max receive is -1 dBm, so
>> an attenuator is certainly highly recommended for short distances.

> "Minimum cabling distance for -LR, -SR, -LX4, -ER modules is 2m,
> according to the IEEE 802.3ae standard"

And?

-A

_______________________________________________
cisco-nsp mailing list cisco-...@puck.nether.net
https://puck.nether.net/mailman/listinfo/cisco-nsp
archive at http://puck.nether.net/pipermail/cisco-nsp/

I asked a transport guy (I couldn't even pretend to be one) and he said that
the answer depends on the equipment. Each device/card should have an
overload rating and a damage rating. Exceeding the former will cause damage
and/or degradation over time and exceeding the latter will cause more
immediate problems. I would purchase the attenuators, they are literally 1
dollar. However, if your in a pinch you can measure the signal levels at
the far end and just make sure that they are not hazardous to your
equipment.

On Wed, Sep 8, 2010 at 5:32 PM, Felix Nkansah <felixnkan...@gmail.com>wrote:

> Hi,
>
> I have Long-Reach STM4 transceivers (can go up to 80km) in a Cisco 7600
> router that is to connect to a transmission device that is just 10m away.
>
> I also have Long-Reach tenGig X2 transceivers for connection to other
> devices that are also just a few meters away.
>
> I am told that using the LR for short distance connections would cause
> problems, but we don't have time to order new transceivers.
>
> Is there a way to set the transceiver interface on the 7600 to adjust to
> the
> short distance? such as changing the transmission power or something?
>
> Your suggestions please. Thanks.
>
> Felix
> _______________________________________________
> cisco-nsp mailing list cisco-...@puck.nether.net
> https://puck.nether.net/mailman/listinfo/cisco-nsp
> archive at http://puck.nether.net/pipermail/cisco-nsp/
>
>
>
_______________________________________________
cisco-nsp mailing list cisco-...@puck.nether.net
https://puck.nether.net/mailman/listinfo/cisco-nsp
archive at http://puck.nether.net/pipermail/cisco-nsp/

>>> *Maximum* transmit power is 4 dBm and max receive is -1 dBm, so an
>>> attenuator is certainly highly recommended for short distances.

>> "Minimum cabling distance for -LR, -SR, -LX4, -ER modules is 2m,
>> according to the IEEE 802.3ae standard"

> And?

The linked document (which you trimmed) specifically says that an attenuator is required for an ER link <20km (underscoring your point), but doesn't mention that requirement for the OP's LR link.

I guess you didn't find the link to information regarding minimum cable lengths, and attenuator requirement relevant to the discusstion?

I hope that the OP, and the commenter running 1m LR links, and the commenter who suggested running short ER links without an attenuator find it useful.

<shrug>

/chris

_______________________________________________
cisco-nsp mailing list cisco-...@puck.nether.net
https://puck.nether.net/mailman/listinfo/cisco-nsp
archive at http://puck.nether.net/pipermail/cisco-nsp/

On 10/09/2010 15:21, Christopher.Mar...@usc-bt.com wrote:
> The linked document (which you trimmed) specifically says that an
> attenuator is required for an ER link<20km (underscoring your point),
> but doesn't mention that requirement for the OP's LR link.

The patch cable length really doesn't matter. What matters is the
attenuation and ensuring that your received light level at each end is
within the threshold of what's acceptable to the transceiver receiver port.

Nick
_______________________________________________
cisco-nsp mailing list cisco-...@puck.nether.net
https://puck.nether.net/mailman/listinfo/cisco-nsp
archive at http://puck.nether.net/pipermail/cisco-nsp/

Nick:

> The patch cable length really doesn't matter. What matters is the attenuation and ensuring that your received light level at each end is within the threshold of what's acceptable to the transceiver receiver port.

So, where does that leave the OP's LR links? Does it boil down to "get a meter"?

Suddenly I'm really interested - I'm about to turn up a bunch of closet switches in an all-singlemode building. All links use LR optics, but some links (to wiring closets immediately above and below) are quite short.

This stuff all ran in staging with 2m patch cords with no apparent problem.

Where attenuators are required, does it make any difference where along the fiber run it's installed (near the sender or near the receiver)?

Thanks!

_______________________________________________
cisco-nsp mailing list cisco-...@puck.nether.net
https://puck.nether.net/mailman/listinfo/cisco-nsp
archive at http://puck.nether.net/pipermail/cisco-nsp/

On Fri, 10 Sep 2010, Christopher.Mar...@usc-bt.com wrote:

> So, where does that leave the OP's LR links? Does it boil down to "get
> a meter"?

10GBASE-LR doesn't need attenuators, and spec requires at least 2 meters
of patch cable.

10GBASE-ER needs a 5dB attenuator to be within spec.

Otoh:

OC192-LR is another beast, it's more closely related to ER/ZR in
10GBASE-space when it comes to specs.

OC192-SR and 10GBASE-LR has very similar optical specs.

--
Mikael Abrahamsson email: swm...@swm.pp.se
_______________________________________________
cisco-nsp mailing list cisco-...@puck.nether.net
https://puck.nether.net/mailman/listinfo/cisco-nsp
archive at http://puck.nether.net/pipermail/cisco-nsp/