With network operators currently facing huge bandwidth demands, various approaches have been explored to meet a projected capacity crunch in the worldwide fiber communications system. To this end, the availability of inexpensive, high-power diodes as pump sources for Raman amplification has generated new interest in Raman technology, which has been commercially available for some 15 years.
Indeed, not only is the role of Raman amplifiers within dense wavelength-division multiplexing (DWDM) networks expected to increase beyond their typical application in long-haul networks, Raman amplifiers have also proven useful for all technology choices that can be used to deploy 100G and above.
The principal advantage of Raman amplification lies in its ability to provide distributed amplification within the transmission fiber, thereby increasing the length of spans between amplifier and regeneration sites. And, because the amplification bandwidth of Raman amplifiers is determined by the pump wavelengths utilized, amplification can be provided over wider and different regions as compared with other amplifier types.
When it comes to meeting the demand for higher transmission capacity, network designers have several options available, from extending beyond the C-band into the L-band to increasing the symbol rate to ≈45 GBd or higher, increasing spectral efficiency through the use of higher modulation formats, or even reducing the spacing between channels at the same modulation format.
Raman amplifiers offer a unique benefit because they provide network designers with the higher optical signal-to-noise ratio (OSNR) required in all of these scenarios.
Of course, to understand the true benefits and advantages, it is important to understand how distributed Raman amplification works in comparison to discrete amplifiers such as erbium-doped fiber amplifiers, or even discrete Raman amplifiers.
In addition, network planners and designers need to take design considerations such as pump power density into consideration in order to optimize gain. Of course, the characteristics of different fiber types, fiber attenuation and Raman pump reach will also have an impact.
To learn more about Raman amplification, from deployment considerations, testing recommendations and how to deal with issues such as backreflection, check out our white paper on how to prepare networks for the next generation of Raman amplification.