CISCO OADM and DWDM

Why Passive 4 or 8 Channel OADM is a very good tool for private ISP and enterprise intranet to expand their IP network.

OTN (ITU-G.709) and MPLS-TP are cool technologies, however, it's way too expensive for most private ISP or typical large enterprise-level IP users like hospital group, or large banks, etc.

Why? Because the target user of OTN and MPLS-TP are typical INCUMBANCY TELECOM companies, rather than IP / ICP / Internet Content users. Such historical orientation leads to a very natural result, that OTN and MPLS-TP are embedded with huge benefits and features in typical pipe-type business (DPLC and IPLC), being necessary for the TELECOM companies to keep supporting their traditional SDH type users.

So what if you simply want to ENLARGE your metro network capacity (typically from couple Gb to 10Gb or 40/80Gb), and say you do NOT have any pipe-type business? Here comes the passive OADM solution supporting 4-8 DWDM channels in a very small footprint. If you just need typical 10G Ethernet on each channel, the cost would be less than 5~7K USD per colored FO interface, then you could easily have a 4~8 x 10GE network.

Typical 10GE DWDM FO transceivers supports === 80Km === distance by default, so for most metro (or even province / county / state level) network, this is good enough for any topology.

Benefits:
1. Saved huge cost on the pipe-type business tools, e.g ROADM, Transponder / Muxponders, making the budget very affordable, typically at the same level of a routing / switching project.
2. All passive optical layer, and could be controlled by Cisco Transport Controller, being very easy to maintain.

Constraints:
--- Being rigid in the optical-layer alignment of resources, needing manual adjustment when any change needs to be done on optical-layer alignment. Any pipe-type service needs to be done has to be arranged on the upper layer, typically the IP layer. The SLA has to be implemented on equipment like ME 3600 / 3800 or ASR 900 / 1000 / 9000 routers.

Therefore, if you suffer from shortage of FO resources, needing to enlarge your IP network capacity, and you DO NOT care much pipe-type services, the above Passive OADM based DWDM system is definitely a good option.

Another option is to simply use 40GE or 100GE on your existing FO network. It's not expensive either. For a 40GE-uplink Cisco switch (e.g Nexus 3000), now the cost is less than 10K per unit. However, the BIG challenge is the transceiver distance, that 40GE or 100GE transceivers ALONE could still only transport 10Km. So if the average of each span in your transmission ring is less than 10Km, a switched 40GE might be useful; if it's higher than 10Km, the passive DWDM makes more sense.

Any discussion is welcomed. 

Morris Hagen, ICI Team - Network Expertise Helps You Succeed

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