Fibre Channel SAN Extension over Optical Networks
Coarse Wave Division Multiplexing
• CWDM also multiplexes wavelengths
• Fewer channels per fiber than DWDM
• Less expensive but less scalable
• Can be implemented using CWDM SFPs
instead of transponders
CWDM “colored SFP”
• CWDM multiplexers are passive,
unpowered, inexpensive devices
Coarse Wave Division Multiplexing (CWDM) is a lower-cost version of DWDM.
As with DWDM, multiple native protocol channels are multiplexed on to a
single pair of optical fibres. However, the wavelengths used by CWDM are
spaced more widely, so CWDM can support fewer FC channels per fibre pair.
Scalability is the primary limitation of CWDM.
On the other hand, CWDM is significantly cheaper to implement. It can be
implemented by installing “coloured” CWDM GBICs and SFPs in the switches
instead of using separate transponders. These coloured SFPs are tuned for
The CWDM multiplexer is also a relatively simple and inexpensive device. A
CWDM multiplexer is typically a passive, unpowered device. The multiplexer is
essentially a very accurate prism that simply refracts the incoming light from
each of the coloured SFPs onto a single fibre.
As a point to point distance we can go up to 120km.