I’ve blogged about Open Cables for quite some time now, as it is, and continues to be, top of mind for submarine cable operators and vendors around the world, and for very good reasons. Open Cables provide operators with greater freedom of choice via a broader and more secure Submarine Line Terminal Equipment (SLTE) supply chain and the ability to select the very latest in modem technology, when and where it’s required.

Can the Open Cable model be simplified, and wet plant capacity further optimized? The answer is yes.

Priyanth+Mehta_Ciena+Submarine+ExpertTo better understand where the Open Cable business model is coming from and where it’s headed, I sat down with Ciena’s resident submarine networking expert, Priyanth Mehta, to get his view on the soon to be published G.977.1 standard by the International Telecommunication Union (ITU), a significant milestone for the submarine networking industry.

In a nutshell, what are open submarine cables?

Open submarine cables are cables that allow the purchaser, wholesaler or Internet Content Provider (ICP), the freedom to choose the SLTE, including coherent optical modems, separately from the submerged wet plant.

Haven’t we been operating in a quasi-open environment for many years?

Yes, upgrades of submarine cables with foreign coherent transponders has occurred since 2008. The ITU-T standards provide agreed-upon definitions for terminal technology acceptance that have supported a quasi-open environment allowing for massive increases in capacity to both existing and new submarine cables.

What are the modeling and link engineering challenges associated with non-standardized Open Cables?

Prior to the acceptance of the Open Cable deployment model, a single vendor was responsible for both the wet plant and modems used. This coupling allowed for an accurate link budgeting process, as all required data was available to the single vendor. As cables began to open up, data required by a modem vendor was held by the wet plant vendor, requiring the cable owner to act as a middleman in procuring this data. Once available, the data may differ from what the modem vendor may expect for their link budgeting process. The standardization of Open Cables makes the data expectations understood from the onset, allowing for high quality link budgeting.

What are the deployment and sign-off challenges associated with non-standardized Open Cables?

Submarine cables are very complex networks and not simply point-to-point systems that some people envision.  The use of Branching Units (BU) can lead to networks with multiple submerged optical paths, which require both testing and acceptance. The process for agreeing on parameters to deliver, and how those parameters will be tested, can be rather contentious with non-standardized Open Cables. The definition of the cable specifications in the upcoming ITU-T G.977.1 Open Cables standard provides the cable owner with the information they need to validate that the cable meets the performance expectations when formally accepting the submarine cable.

In your mind, what should be formally standardized to facilitate Open Cables?

Defining both the parts of an Open Cable, along with the parameters of importance required to describe the cable performance, is important to standardize. The ITU-T G.977.1 does a good job in achieving this goal.

Can you tell us about the SubOptic Open Cables Working Group and its goals?

The SubOptic Open Cables Working Group was created to bring together a wide range of industry experts, from both vendors and operators, who could provide guidance and input on the parameters that were being proposed for standardization and how to apply that information to real world applications when procuring, accepting, and upgrading submarine cables.  The working group presented their initial white paper at SubOptic 2019.

What about the new ITU-T G.977.1 standard and its industry benefits?

G.977.1 is a comprehensive Recommendation that describes all the parameters and processes wet plant vendors use to design, commission, and accept a submarine cable system. In addition, several example templates are provided to give customers and operators a detailed examination of the performance under a given terminal technology configuration. Modem vendors can also use this information to produce accurate assessments of capacity and power budgets.

What was Ciena’s role in the development of the new ITU-T G.977.1 standard?

Ciena is a contributor to many ITU-T Study Groups and Questions. Question 8 leads the development of all submarine related Recommendations and Ciena has been a contributor for many years and led the editorship of G.977.1. The Editor is responsible for drafting the document, providing guidance, and revising this material with the inputs of Question 8 experts. It took several years of negotiations and delegations with the industry experts on the Recommendation structure, technical content, procedures, references, and many more items.

Any final thoughts on where the submarine cable industry is or should be headed?

Design, commissioning, and acceptance of submarine cables are a well-oiled machine. We continue to make unique technical observations for each cable system that ultimately drive requirements for future transmission technologies. Consequently, we’re entering a new generation of hardware, with feature sets so broad that our understanding of fundamental performance parameters, such as the Q-factor or Bit Error Rate (BER), may not scale efficiently. The ITU-T and the industry will continue to work together and progress this area, as new approaches in performance metrics are demonstrated.

Learn more

You can learn more by listening to Priyanth’s “Understanding the New Standardized Recommendations on Open Submarine Cable Acceptance” presentation from Submarine Networks World 2020.

You can also download our free handbook here.

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