The Nu-Wave XLS is a high-performance unrepeatered DWDM system that delivers an unprecedented combination of capacity and reach for both new systems and upgrades of existing systems. When used in upgrades, the Nu-Wave XLS is able to extend the life of existing unrepeatered subsea systems by providing capacity above and beyond the initial design, without having to deploy a new cable.
The Nu-Wave XLS performance in terms of reach and capacity is unmatched in the industry. Traditional unrepeatered DWDM products typically couple Raman amplification with the more conventional Erbium-Doped Fiber Amplification (EDFA) to bridge longer distances. By eliminating the use of EDFA altogether, the Nu-Wave XLS exploits the full potential of all-Raman amplification to simultaneously provide a significant improvement in both distance and capacity.
The Nu-Wave XLS helps operators to reach new markets, by allowing access to places previously accessible only via more expensive satellite or repeatered systems. In effect, the Nu-Wave XLS helps to close the “digital divide” and to spread the globalization of broadband services by:
- improving connections to resources
- reaching underserved markets
- providing same type services as available on mainland
The Nu-Wave XLS can help generate new revenue streams via the distribution of these new services, for example video or gaming applications. By extending the life of existing unrepeatered systems, the Nu-Wave XLS postpones a heavy capital investment such as the deployment of a new cable.
Finally, its support of advanced IP and wavelength services (GbE – 40 Gb/s) in a space saving 600 Gb/s single rack configuration saves operators on OpEx.
In summary, the Nu-Wave XLS offers:
- An elegant, cost-effective solution for long-reach, high capacity unrepeatered links.
- An alternative to more expensive solutions requiring either Remote Optically Pumped Amplifiers or repeaters to bridge span distance.
- Maximum capacity on all fiber types, including “DWDM-challenged” fibers (LS™, DSF).
Nu-Wave XLS offers this unprecedented combination of reach and capacity using industry proven transmission techniques along with state-of-the-art amplification technology. It maximizes the benefits of all-Raman amplification by tightly integrating distributed Raman and discrete (or lumped) Raman amplification in an innovative and patented way. Commercially available XLS line terminating equipment has been used to demonstrate transmission of 8 channels at 10 Gb/s over 440 km. This result was accomplished without the use of in-line devices, such as Remote Optically Pumped Amplifiers (ROPA), or advanced modulation schemes. With the same terminals, equipped with 40G transponders, the transmission of 10 channels at 40Gb/s over 468km (82dB of loss) was achieved.
When deployed using the latest developments in transponder technology and ultra-low loss fibers, specifically developed for submarine unrepeatered applications, the reach of the Nu-Wave XLS approaches 500 km.
To date, the Nu-Wave XLS has been used to deploy the longest reach (393 km), high-capacity (190 Gb/s) unrepeatered system in the world. To further extend this range Xtera has designed the XLA, a configuration of the Nu-Wave XLS , that can be deployed when a submarine cable reaches land. The XLA can be located at the landing site to extend the capacity of the cable to a city POP or potentially on an island between two long unrepeatered submarine segments.
Raman Amplification Overview
A Raman optical amplifier is based on a different physical principle than conventional optical (rare-earth doped) amplifiers. In a Distributed Raman Amplifier (DRA), pump lasers are connected to the line fiber and transmit optical energy down the length of the line fiber. As it passes along the fiber this extra energy interacts with the optical signal increasing its strength. Since the amplification is distributed along the length of the fiber Raman amplifiers have some significant advantages. First, the distances between amplifiers can be stretched further even when pumped from only one end of the fiber. Where extra distance is required the fiber can be pumped from both ends, further increasing the distance. Secondly the distributed amplification provides a much improved Optical Signal to Noise Ratio (OSNR) performance compared to conventional optical amplifiers. This makes it possible to increase the number of cascaded amplifiers enabling very long links (3000 km) without the need for regeneration. In a Discrete (or Lumped) Raman Amplifier (LRA), gain is provided in Dispersion Compensating Fiber (DCF). So, as an added benefit, an all-Raman amplifier (which combines DRA & LRA) not only provides gain but also provides dispersion compensation, thus limiting the need for external Dispersion Compensation. Finally the optical bandwidth of a Raman amplifier can be increased by adding extra pump lasers at different wavelengths. This makes it possible to transmit many more optical signals (up to 240 wavelengths) on a single fiber than a typical EDFA-based system (80-96 wavelengths). As a significant side benefit, the multiplicity of pump lasers results in a more robust amplifier (a defectice pump laser could be overcome by its neighbors), leading to higher system reliability and thus network availability.
Nu-Wave XLS Implementation
Place mouse over areas of diagram for descriptions