1. Adding CWDM to single wavelength Networks
This application note describes how to use a passive optic MUX/DEMUX to add
CWDM wavelengths to 1310/1550nm single wavelength network rings.
Enterprises and service provider have traditionally been building their gigabit speed
metro networks with 1310nm and 1550nm wavelengths. This network has consisted of a
pair of fibers connected between two or more buildings with a SONET ADM (or Ethernet
switch) at each building. Figure 1 shows a diagram of this application.
B u ild in g 2 B u ild in g 1
SONET
SONET O C -1 9 2
ADM
ADM 1310nm
40km
Figure 1. Single wavelength 1310nm link application
When additional bandwidth is needed between the two buildings the user adds either
more fiber between the buildings or implements an expensive DWDM solution.
With the advent of CWDM transceivers and passive optics, a simple low cost solution is
possible by adding a WDM MUX/DEMUX at each end with additional CWDM
wavelengths. Figure 2 depicts an example of this solution. Note that with two additional
CWDM wavelengths an Ethernet and Fibre Channel switch are deployed.

2. Adding CWDM to Single Wavelength Networks
Building 2
Building 1
1310nm/OC-192
1470nm/1.25G Ethernet
1510nm/2G Fibre Channel
40km
SONET 1310/CWDM MUX 1310/CWDM MUX
ADM
SONET
ADM
Ethernet
Sw itch
FC
Sw itch
Ethernet
Sw itch
FC
Sw itch
Figure 2. 1310nm link upgraded with additional CWDM
Wavelengths.
Implementing the Solution
The upgrade solution is simple and cost effective. At each node in the network add a
passive MUX/DEMUX with a single network side port and a 1310nm port with
additional CWDM ports on the equipment side. The 1310nm wavelength is completely
transparent to the added CWDM wavelengths. Up to 8 CWDM wavelengths can be added
as the bandwidth requirements grow without interruption to the existing service.
The following block diagrams show how to upgrade a network using passive
MUX/DEMUXs to insert and de-assert optical CWDM wavelengths from an existing
single 1310 wavelength ring. Each step in the process of building the ring is shown below
with an equipment view, node view and network view.
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3. Adding CWDM to Single Wavelength Networks
Equipment View
The equipment block diagram view, shown below, illustrates how to add/drop CWDM
wavelengths to/from a 1310 wavelength ring network by connecting a 1310/CWDM
MUX/DEMUX to a four channel CWDM MUX/DEMUX. The 1310/CWDM
MUX/DEMUX connects to the network and splits the 1310nm wavelength from the
CWDM group of wavelengths. After being connected to the 1310nm CWDM port, the
CWDM MUX/DEMUX breaks out each of the individual CWDM wavelengths, which in
turn go to an Ethernet switch.
Jumper CWDM
Port to Network
To Network Port of CWDM
MUX/DEMUX
SC SC
Network 1310/CWDM MUX/DEMUX Net k
wor CWDM MUX/DEMUX Expansion
Plug-In Plug-In Port
1310 CWDM Port 1470 1510 1550 1590
SC SC SC SC SC
SC
1RU Rack Mount
To 1310 Transceiver
To Ethernet Switch
Plug-In front panels views of the DEMUX/DEMUX equipment:
1310/CWDM MUX/DEMUX
CWDM MUX/DEMUX-4-EX
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4. Adding CWDM to Single Wavelength Networks
Node View
The node view, shown below, illustrates two sets of 1310/CWDM MUX/DEMUXs with
CWDM MUX/DEMUXs connected to an Ethernet switch to make a protected node. The
1310 wavelengths are cabled separately to the 1310 network equipment.
To Network WEST To Network EAST
1310/CWDM Network Newor
t k Network Newor
t k
CWDM
MUX/DEMUX
1310 CWDM Port 1470 1530 1570 1590 1310 CWDM Port 1470 1530 1570 1590 MUX/
Plug-In
DEMUX
Plug-In
CWDM
To 1310 CWDM Transceivers
To 1310
Equipment Transceivers
Equipment
Ethernet
Switch
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5. Adding CWDM to Single Wavelength Networks
Network View
The network view, shown below, shows how to build a three node network with the
protected node design shown above.
1310 1310
Equipment Equipment
Long Distance Fiber
Link
Network
WEST Network
WEST
1310/ 1310/
CWDM CWDM
MUX/ MUX/
DEMUX DEMUX
Pair Pair Ethernet
Ethernet
Switch Switch
1310/ 1310/
CWDM CWDM
Network
MUX/ MUX/
DEMUX WEST DEMUX
Pair Pair
Network
EAST Long Distance Fiber
Link
Ethernet
NODE 2 Switch
Long Distance Fiber
Link
NODE 3
Network Network
WEST EAST
1310/CWDM MUX/ 1310/CWDM MUX/
DEMUX Pair DEMUX Pair
CWDM
1310 CWDM
1310 Ethernet
Equipment
NODE 1
Switch
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6. Adding CWDM to Single Wavelength Networks
Summary
The solution shown in this application note illustrates how to simply upgrade a 1310nm
single wavelength network ring to a WDM network ring with four additional
wavelengths. Further, the expansion need not be limited to four wavelengths. By adding a
8 channel CWDM MUX/DEMUX in place of the 4 channel CWDM MUX/DEMUX, 8
CWDM wavelengths become available on the network ring. For future bandwidth that is
beyond the capability of 8 CWDM wavelengths, insert a DWDM MUX/DEMUX into the
CWDM MUX/DEMUX for creating 45 more wavelengths with DWDM on CWDM (see
Optics Central’s app note for DWDM on CWDM).
Finally, this solution is also available to single wavelength networks deployed with
1550nm. In the above solution, substitute the 1310nm MUX/DEMUX with a 1550nm
MUX/DEMUX that splits the 1550nm wavelength from the CWDM wavelengths.
For additional information see Optics Central app notes:
“The WDM Metro Access Solution”
“Implementing DWDM on CWDM”
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