DWDM SFP modules - where to use?

[Todd Bren]

Hi, we are considering to interconnect two sites using DWDM. What type (colored, non-colored 1310) SFP modules should we use on our switches connecting to multiplexer/OADM? Does it depend on the actual MUX device?

[Tom Randstrom · Accepted solution]

DWDM multiplexers and OADM filters have wavelength specific ports, that are connected to an optical transceiver of the same wavelength.  Below is a link to the Cisco DWDM pluggable optical transceivers,

http://www.cisco.com/en/US/products/ps6576/index.html

The Cisco options for DWDM filters are linked below:

http://www.cisco.com/en/US/prod/collateral/modules/ps5455/product_data_sheet0900aecd806a1c36.html

http://www.cisco.com/en/US/products/hw/optical/ps1996/products_data_sheets_list.html

Optical transceiver to hardware compatibility

http://www.cisco.com/en/US/products/hw/modules/ps5455/products_device_support_tables_list.html

Let us know if you have additional questions. 

[Todd Bren]

Hi Tom, with CWDM, would we need just CWDM-MUX8A, one pair of dark fiber for transport and SFPs with specific wavelenghts on LAN side? In other words, without OADMs?

We need 6 point to point links between two locations. No CWDM ring is necessary.

[Tom Randstrom]

Yes, a pair of the CWDM-MUX8A mux/demux modules + 2 dark singlemode fibers + 6 pairs of the appropriate wavelength CWDM SFPs, and you will have 6 point-to-point links (6 pairs of virtual fibers) with two links to expand to. 

You didn't mention the fiber length between the two data centers.

The current Cisco CWDM SFPs are only available at 1GE.  The Cisco DWDM solutions operate a 10GE (SFP+, XFP, X2, XENPAK) or higher rates.

[Todd Bren]

Length is some 34 kilometers. What is the operational distance of Cisco CWDM SFP modules (via passive CWDM-MUX8A)? Would we need external optical signal amplifiers?

[Tom Randstrom]

34 kilometers is well within the operation of the CWDM solution.  Presently, optical amplification is not available for CWDM, because the wavelengths are outside the amplifer band of a standard EDFA.  

[Todd Bren]

Thank you for all answers. I will mark one of these as correct. But prior this I'm curious what is the operational reach of Cisco CWDM modules with usual 0.25dB/km link loss? How to do the math?

Cisco CWDM specs:

http://www.cisco.com/en/US/prod/collateral/modules/ps5455/ps6575/product_data_sheet09186a00801a557c.html

[Tom Randstrom]

This link has a good tutorial on calculating optical links.  You will need to add the CWDM-MUX8As filter loss for each end (2 x 2.2dB = 4.4dB) to their calculations. The CWDM optical transceivers have a Transmit of +1dBm and Receive of -29dBm. 

I hope this helps!

[Todd Bren]

Hi Tom,

I've been busy a few days, so a bit late reply. Thanks for the calc now I got the numbers. One last question, as there are still two unused channels in CWDM I'm thinking of extending core interlink as well (for DR purposes). However this one must be 10G.. It seems that only 1G CWDM speeds are supported on Cisco side, is this true?

So when I want to add 10G channel to 6x1G CWDM channels then is the only choice to use DWDM SFPs on core interlinks via two additional EWDM muxes (EWDM-MUX8)?

Thank you, after this I will select the correct answer, promise!

[Tom Randstrom · Accepted solution]

Currently, Cisco only supports CWDM at 1Gbps.

Your solution of CWDM-MUX8A and EWDM-MUX8 would support your described application. FYI.... if the EWDM muxes are not installed day 1, the upgrade will be service impacting as the CWDM muxes feeds through the DWDM muxes.

Another option would be to deploy your network using just the EWDM-MUX8s with 1G and 10G DWDM optical transceivers. May increase the total network cost, but only requires one filter module at each end.

Hope this helps.