DWDM and CWDM Multiplexers

[ahami]

I have questions about DWDM and CWDM multiplexers and connecting different devices to them.

1)   There are various devices that use a port of 1550.00 nm, and as far as I know, DWDM multiplexers have a channel with a wavelength of 1550.12 nm while the passband is 0.11 nm. I want to know what is your solution for connecting the 1550.00 nm port of other devices to the 1550.12 DWDM input or other inputs?

2)   Due to the fact that CWDM multiplexers cover a shorter distance than DWDMs. I want to know approximately how far Cisco CWDMs generally cover.

[Tom Randstrom]

1) If the 1550.00 and 1550.12 transceivers are interconnected over a pair of fiber cores, not carrying any other DWDM wavelengths, then the two will interoperate. That said, in a typical DWDM network, all the client equipment attaching to the CWDM link will support the CWDM transceiver modules.  

2)  The distance of the link will typically depend upon the number of CWDM channels (mux/demux) and the reach of the selected optical transceivers. 

[ahami]

Hi. Thank you for your reply.
A) What if we use a single fiber instead of a pair of fibers?
B) I still did not get an exact answer. What is the solution for connecting 1550.00 nm ports of other switches and routers to DWDM ports?
C) If the CWDM has 8 or 16 channels, what is the approximate distance that can be covered?

[Tom Randstrom]

A) What if we use a single fiber instead of a pair of fibers?

There are CWDM mux/demux filters designed for single fiber or 2 fiber deployments.

B) I still did not get an exact answer. What is the solution for connecting 1550.00 nm ports of other switches and routers to DWDM ports?

Typically, if you wanted to use a standard 1550nm signal in a CWDM network you would use an outboard transponder module, which takes 2 transceivers, one for the 1550nm and the other for the CWDM 1550.xx nm. The 1550.xx would be attached to the mux/demux.
In CWDM system, you cannot add a standard 1550nm wavelength signal into a CWDM mux/demux port. It requires a narrow optical signal.

C) If the CWDM has 8 or 16 channels, what is the approximate distance that can be covered?

An 8 channel CWDM operating over 2 fibers at 10GE has a link reach of approximately 36km.

Not sure what your situation is so feel free to explain.  

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[ahami]

Consider a network consisting of SDH switches, MPLS routers, and OTN switches. Most of these work at wavelengths of 850, 1310 or 1550 nm. In addition, we have other equipment in the power system, such as differential protection relays. If we're going to put the traffic related to all this on a single fiber, we have to use DWDM multiplexers. As far as I know, DWDM multiplexers work passively and we want to use active equipment less as much as possible. However, there are challenges: Using DWDM is more desirable due to a large number of channels and coverage distance, but it will be challenging due to the narrow passband (0.11 nm) and not matching with the operating wavelengths of interfaces of other devices. But the use of CWDM is suitable because of the wider passband (20 nm) and support for wavelengths of 1550 and 1310 nm, but it has fewer channels and covers a shorter distance, which is not good.

[Tom Randstrom]

When you have legacy equipment that doesn't have integrated xWDM wavelength
modules, the purpose build xWDM systems from Ciena and Adva are needed to
do wavelength translation. Most of these are DWDM based. CWDM was developed
as a lower cost, lower capacity systems that typically used pluggable
client optics (SFP, GBIC) within the end terminal devices.

[ahami]

Hi.
Thank you for your responses.
I recently encountered doubts and questions. The distance covered by the passive DWDM and CWDM multiplexers we have talked about so far(like 100 km covered by DWDM MUX or below 40 km covered by CWDM MUX), is this the distance between only two MUXs, or do we need an amplifier between them?

[Tom Randstrom]

CWDM cannot be amplified, so it's distance is between muxes. 100km over
DWDM is amplified and is the typical spacing for equipment huts in backbone
networks.

[ahami]

Is there a solution to reaching a distance of 100 km without using an EDFA or any active device?

[Tom Randstrom]

Single channel, not DWDM or CWDM.