Connecting data center services in a scalable and controlled way

The business case for embedded DWDM over a carrier-managed service

Several methods are available for connecting data center services in an enterprise network. Companies can run the network by themselves in a private network or have an operator run it for them through a managed service. In some cases, if the fiber isn’t available the enterprise has no choice but to contact an ISP or MSO and lease the required data traffic as individual managed services. But if fiber is available, owning and operating an embedded WDM network can bring both commercial and technical benefits.

Owner-managed private network using embedded WDM technology

If dark fiber is available, embedded WDM makes an attractive option for connecting data center services. It gives you the ability to transport up to 80 individual traffic channels over a dark fiber network. It works on the same principle as a simple ELWL circuit except the ELWL transceiver is replaced by a CWDM or DWDM variant connected directly in to the SAN or IP switch. Instead of being connected on to the line fiber, these DWDM signals are connected by an LC patch cable to a passive multiplexer (a 1U fiber termination unit), which gathers them together and transports them over a single dark fiber link.

Carrier-managed wavelength services

With a carrier-managed service, each individual service needs to be leased from the service provider. So, if eight channels are required then eight services need to be purchased. A service contract is normally purchased over a two- or three-year period. The ROI calculation that the service provider uses is based on a return over six months, with the monthly payment usually staying the same for the remainder of the contract.

While a service provider is normally efficient with Ethernet and Sonet/SDH services, they are not so adapted to Fibre Channel traffic. This means that for connecting corporate data center services, the efficiency and latency of the network tend to suffer. A carrier-managed service usually requires the FC switch to be run in R_Ready mode, which tends to limit some of the functions from the switch. And the OEO (optical-electrical-optical) nature of the equipment used impacts latency, which is often key in certain applications.

Carrier-managed circuits

Embedded DWDM

Individual services vs. Embedded DWDM
  • No ownership of network or control of new circuit uptime
  • Telecom equipment used, not aimed at enterprises
  • FC switch must be in R_Ready mode
  • R_Ready removes the FC proprietary functions
  • FEC in the FC switch must be disabled
  • Expensive and inflexible networking
  • Ongoing opex soars higher
  • Up to 88 channels over a single fiber pair
  • ELWL approach with DWDM transceiver and multiplexer
  • New channels easily added just by adding SFPs
  • Any mix of SAN & IP traffic, up to 80 channels
  • Just a single fiber pair required
  • Low TCO, no hidden opex, quick ROI
  • More budget freed up for other areas of the network
  • No power, small footprint, green data center networking

Graph showing how the opex with managed services compares to the TCO of running an embedded DWDM system

8-channel 16Gbps embedded WDM system

Investment (first 3 years)
1 x Embedded DWDM system $68,000
Capital expenditure (capex): $68,000

Continual operational costs (for 3 years)
Fiber leasing costs $36,000

Total cost (3 years): $104,000

8 managed services from carrier

Investment (first 3 years)
Eight channel active DWDM system cost $69,730
Monthly lease based on 6 month ROI for carrier $11,622

Continual operational costs (for 3 years)
Monthly equipment rental $11,622
Monthly fiber rental and service cost ($1000/month) $12,000
Total opex cost/month: $19,622

Total cost (3 years): $706,392


The carrier-managed service is based on a capital equipment cost of $70K for an 8-channel 16Gbps DWDM system with ROI required after 6 months, which results in monthly fee of $12K for the equipment rental and $8K per month for the fiber and service costs.

The embedded DWDM platform is based on a fiber rental cost of $1000/month and $50K for an 8-channel system.

The clear benefits of dark fiber and embedded DWDM

Without a doubt, using a managed service enables you to transport data between customer sites. But this approach is expensive to scale when you need more services. A service is only available if there is an existing fiber optic network between the sites anyway. And for the opex costs over the period of the service, it pays to investigate the cost of purchasing a dark fiber connection. In the end, you’ll gain a more flexible and scalable solution to the growing demands for bandwidth.

Embedded DWDM offers the same capacity as an active transponder-based DWDM platform, but in a much simpler way. With a passive multiplexer at the heart of the system, you eliminate unwanted heat or noise emissions, keep space to a minimum, and gain the ultimate green data center DWDM network. New services are quickly and conveniently added just by adding the required number of optical transceivers. Embedded DWDM — it really is that simple.

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