What Is L-band?
Submarine networking has long been—and, in many cases, still is—the unknown, yet critical, part of the global Internet. Terrestrial networks (and, to a lesser extent, satellites) have been the most visible networking cogs. Of course, terrestrial networks serve as critical links, but they stop at the coastlines. And satellites carry a tiny fraction of data traffic around the world.
The fact is, submarine cables carry upwards of 99 percent of global Internet traffic between continental landmasses. Current growth trends show no signs of letting up. With channel capacity limits fast approaching and little appetite for adding cables, how can submarine cable operators add sufficient submarine capacity to satisfy insatiable demand?
About a decade ago, the terrestrial fiber industry faced a similar situation. The technology of the time—which used On-Off-Keying (OOK) to shutter a laser on and off to send digital ones and zeros through an optical fiber—had its limitations, especially when compared to current coherent optical transmission technology. Nonetheless, it worked well at the time, and was able to maintain pace with relatively modest demand growth.
But as broadband took off with video and other bandwidth-intensive applications became increasingly popular, the industry suddenly faced the immutable laws of physics—you can only squeeze so many 10G channels into a single fiber pair.
Deploying more terrestrial optical line systems was not always practical, and technologies such as 40G were not yet realities. The industry had to face reality: it needed to get more out of the fiber plants already deployed.
So the focus turned to better utilizing the existing wavelength bands in the already deployed fiber. Traditionally, fiber providers used the C-band, which runs from approximately 1530nm to 1565nm. They were able to space numerous 10G channels very close together through the fiber. But on very high-capacity and constrained routes, this approach was quickly reaching its limits, so the industry started using adjacent optical spectrum, known as the L-band, which runs from approximately 1565nm to 1625nm.
Now, in yet another example of technologies originally conceived in the terrestrial realm finding their way beneath the seas, the submarine industry is looking to utilize L-band to increase line capacity.
Vendors with extensive L-band terrestrial network experience can take that existing knowledge and real-world field experience to reliably adapt and incorporate L-band modems into their existing Submarine Line Termination Equipment (SLTE) to support both C-band and L-band, effectively doubling the available optical spectrum and the addressable revenue along a submarine route. At the same time, this combination offers greatly improved economies of scale. Expanding beyond the C-band to the L-band also enables the introduction of new and differentiated services based on Spectrum Sharing, which uses virtualization for the logical partitioning of the optical spectrum in a submarine optical fiber pair between different end-users. As such, each end-user sees only their dedicated ‘virtual’ fiber pair, which is a subset of the overall spectrum of the same, shared physical fiber.
L-band, or long band, is a wavelength band immediately adjacent to the C-band that has been used for a decade to expand capacity of terrestrial networks. It is now being evaluated for use by submarine network providers.
How Ciena helps
Ciena, with deep expertise in both terrestrial and submarine networks, enables submarine cable operators to mix and match building blocks to create purpose-built network solutions that can utilize both C-band and L-band. While adding that flexibility, Ciena continues drive change in the closed and proprietary nature of submarine networks. Submarine cable operators can now easily choose the best terminal equipment technology for the right cost from any vendor.
Every day, submarine cables carry more than US$10 trillion in transactions—the very definition of critical infrastructure. Bandwidth consumption will grow at more than 40 percent CAGR over the next few years in all regions. So utilizing a solution like Ciena’s will enable submarine providers to get more out of their existing infrastructure. Ciena’s GeoMesh Extreme helps you overcome the challenges of submarine networks with four categories of available components—all of which can be mixed and matched to address your specific business needs.
- Optical: Submarine WaveLogic Ai, Liquid Spectrum™, WaveLogic Photonics, L-band support, and integrated test capabilities
- Switching: 5430 Packet-Optical Platform, 6500 Packet-Optical Platform, 8700 Packetwave® Platform, and OneConnect intelligent control plane
- Management: OneControl Unified Management System, Blue Planet V-WAN for agile connectivity, Blue Planet Manage, Control, and Plan (MCP), and Blue Planet Multi-Domain Service Orchestration
- Services: Cloud-based SLA Portal, PinPoint Coherent Optical Time Domain Reflectometer (C-OTDR), Managed NOC, network health, topology discovery, and alarm correlation
How GeoMesh Extreme is being used and rolled out
Looking to expand into L-band wavelengths, submarine cable operators are turning to GeoMesh Extreme for its unique architecture that leverages both submarine and terrestrial technologies. But GeoMesh Extreme also provides a wealth of additional benefits to submarine networks, such as the analytics and machine learning capabilities that come with a Software-Defined Network (SDN).
Other GeoMesh Extreme features and services include:
- SLA Portal, which dramatically improves customer satisfaction and retention by providing transparent visualization of service performance. Customers can self-diagnose network service health and verify SLA performance assurance
- PinPoint C-OTDR, which provides visibility into the performance of multiple segments and systems of submerged plant. It also enables remote access to C-OTDRs in various sites from a centralized NOC/data center
- Ciena’s Managed NOC services, which extend your customers’ business with the networking skills and experience required to manage their network infrastructure, provision bandwidth growth, and minimize network downtime that impacts critical business processes
- Network Health Predictor, which utilizes big data analytics to enable you to proactively identify and address areas where network issues and faults might occur
- Topology Discovery, which ensures you can utilize the network to maximum capacity by revealing actual network connectivity, stitching circuits, and identifying stranded bandwidth
- Alarm Correlation, which groups events to reduce the number of issues you need to investigate. Because it identifies related alarms and targets them simultaneously, you don’t spend as much time troubleshooting
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