In Raman amplification, the fiber is used as the medium for amplification. An optical beam – or, “pump wave” – is launched at an appropriate wavelength into the fiber. The data signal propagating across that wavelength is amplified as the optical beam releases its energy. In this technique, amplification is distributed over the length of the fiber strand, as opposed to being limited to discrete amplifier sites in the case of Erbium-based amplification (Figure 2).



Figure 2: Raman amplification in transmission fiber.

Pump-induced Raman scattering provides amplification of the data-carrying signal in new and already-installed transmission fiber, boosting performance beyond that achievable with conventional Erbium amplifier technology.

With Raman amplification employed, synchronous storage applications of speeds up to 10Gbit/s can be supported across distances of 200 km. Because it relies on the optical fiber as a medium for amplification, Raman amplification does not require doping of the fiber. This means that Raman amplification can be performed on an enterprise’s or managed service provider’s already-installed base of single-mode fiber. And eliminating the amplifier sites necessary in Erbium-based amplification slashes costs, improves transmission characteristics, abstracts away security concerns and increases survivability of a data mirror by allowing longer optical links between storage data vaults.

Amplification also can be based on a combination of Raman scattering and in-line Erbium-doped amplifiers. High-performance, hybrid Raman/Erbium amplifiers are emerging that enable asynchronous storage applications to be supported over even longer distances. Fewer amplifier huts are needed than if Erbium-based amplification alone was used, and the enterprise’s CAPEX, EFI&T and OAM costs are cut accordingly.


Conclusion

The cost savings to be realized in reducing or eliminating amplifier hut sites should not be underestimated. CAPEX, EFI&T and OAM burden all stand to be cut. Consider, too, that leased office space may run an enterprise as much as $1,000 to $2,000 per month when power and air conditioning are included. Elimination of just a single mid-span amplification site along a 200-kilometer link could save the enterprise up to $100,000 over a five-year period. The economic argument for Raman amplification in enterprise networking is strong.

In context of storage services, the ability to lengthen the distance between data vaults rates is an even more compelling benefit. To gain the protection they want (and governments more and more frequently require), enterprises must be able to put more distance between their primary and backup data centers. Raman amplification cost-effectively delivers that capability.