Open Optical Networks (OON): The new paradigm for multi-vendor Optical networks

It is the choice of network operators to decide how fast and how far, they want to have transition — from a proprietary network to a fully open architecture

By Dr Anuj Kumar Srivastava

Optical communication systems have been a closed-end to end proprietary infrastructure consisting of an optical system, transponders at both ends, a line, and a management system. In this conventional optical network, architecture components were supplied by a single vendor with proprietary rights. While the concept of disaggregated or open optical components is an open interface or non-proprietary interface. This enables the service providers to purchase different components from different vendors and assemble a system themselves in the most optimized, innovative, and cost-effective manner.

This concept of openness in optical network architecture facilitates a multi-vendor solution and enables to mix and match devices from different vendors with the expectation to have the greatest innovation that the broadband industry provide can provide.

Such network is called Open optical networking and describes an optical network that uses open standards and commodity hardware and components which provides network operators with more choice and enables each function of the node to innovate in its own manner because of disaggregation of transponders and line systems. Open Optical networking enables interoperability and data exchange around a set of equipment from different vendors in a network. This enhances expandability and extendibility — in both hardware and software - in the optical network.

Network operators and service providers can reap benefit from open Optical networking system because of number of choices of hardware and software as they have not to depend on a single vendor.

Advances in silicon performance improvement cycle described by Moore’s law, the advent of Coherent optical transceivers, and research in photonic technology provide a faster innovation cycle relative to the conventional optical line system. Network operators and service providers can reap benefits from an open Optical networking system because of a number of choices of hardware and software as they have not to depend on a single vendor. Out of various benefits that come from open networking, the most important is the potential to save in cost compared to proprietary vendor products and the extra flexibility in configurability.

Motivation for Open Optical Networking- Increasing Traffic Demands

A number of research reports have found and given indications about the increasing traffic demands on our networks. In the era of Covid-19, the importance of networks has been greatly realized– not only for entertainment but for remote learning and work-from-home also. Anticipated Annual Traffic Growth by Network Segment is depicted in Figure1.

Such a high anticipated traffic growth is a strong motivation for service providers to reconfigure and switch to open optical networking with non-proprietary and multi-vendor components at lower costs.

There is an indefinitely increasing array of bandwidth-hungry applications with the ever increase of digital traffic coming out of social media, multimedia services, VoIP, mobile applications, and cloud computing. With the growth of the Internet of Things (IoT) and Machine-to-Machine (M2M) communications, an explosion of data is being generated. Therefore, this will give a potential impetus to the growth of the optical transport network market.

Hence, the tremendous growth of digital traffic will have a substantial positive effect on the optical transport network. To minimize losses because of system failures, service providers depend on high-speed optical transport networks. The widespread pandemic of the COVID-19 has also resulted in a major disruption in the supply chain of telecom infrastructure. So the ever-rising requirements for home connectivity, digital health, and also even economic indexing measures may give a boost to low cost, highest reliability, and lowest latency optical connectivity.

This has given birth to the idea of an Open Optical Network. Since 2017, optical transport networks have seen the emergence of various initiatives for transformation culminating into an open optical architecture similar to the emergence of the open 5G Radio Access Network (OpenRAN) and open architectures in the data center, etc.

The benefit of Open Optical Networking

The objective of more and more openness a to get rid of vendors’ monopoly over proprietary infrastructure and to enhance supply chain resilience by having multi-sourcing options. By incorporating SDN and orchestration, the network becomes smarter, more capable, and grows in scope. Simultaneously open interfaces also grow in relevance and importance. Applications of well-defined standard protocols and open-source code versus proprietary APIs, greatly simplify the Integration efforts.

Open Optical and disaggregation networking give impetus to optical networks with an enhanced velocity of the innovation cycle, economic benefit, and evolution as the telecommunications industry matures. Such evolution can be seen across a number of areas in networking, including open RAN initiatives for 5G. As per ACG Research Survey report 2021, service providers are anticipating a are number of benefits

Three top envisaged benefits of Open Optical Networking are:

1. Increase the Innovation Velocity of Optical Network

Leverage of innovation capabilities of network operators can be enhanced regarding the entire optical ecosystem by disaggregating the optical network into functional blocks depending on their innovation cycle, by selecting the best-in-class technology from any vendor. The increased pace of velocity of innovation is another benefit of open optical networking. On separating the network functions each of them becomes capable to innovate itself at its own pace. The innovation ecosystem which is expanded further simplifies the integration of new technology with YANG data models and with open APIs, etc. This is in contrast to the traditional network where up-gradation of the networks are entirely based on the capabilities of innovation of the single vendor regarding the propriety interface.

2. Optimize and Differentiate with Multivendor Solutions

With the implementation of open optical networking, network operators or service providers can build a more tailored network with the help of the combination of the best technology from each vendor which gives them a competitive advantage. Open optical networking also immensely increases the scope for operators to build a network that optimally meets their specific needs and provides a platform for differentiating their services.

3. Transform the Economics of Optical Network

Open optical networking enhances tremendous economic benefits to the operators and service providers by enabling them to scale up the capacity of their networks within the scope of budget limitations. Accelerated innovation speed is the most important driver for reductions in cost-per-bit in Open optical networks. Because by doing so, each generation of coherent technology offers an additional step of change in increase in capacity-reach, This reduces footprint and power consumption. By enabling a multivendor option, the economic benefits of ecosystem-level innovation are quickly realized in the entire network lifecycle. The flexibility and option to select the best products in a multivendor scenario for each layer and domain independently rather than purchasing whole solutions from a single vendor only is one more reason for a better economics

Optical Industry Evolution to Openness and Disaggregation

This evolution is now enabling and facilitating optical networking to take advantage of the principles of openness and disaggregation by separating the two key primary functions in optical networks i.e. optical line systems and transponders and also by minimizing challenges with the help of disaggregated optical solutions and by reducing the operational issues arising due to multi-vendor networks.

Open Optical and disaggregation networking gives impetus to optical network with enhanced velocity of innovation cycle, economic benefit and evolution as telecommunications industry matures. Such evolution can be seen across a number of areas in networking, including open RAN initiatives for 5G. As per ACG Research Survey report 2021,

These aspects of openness are arrived at by using coherent transceiver technology; adopting line systems along with flexible grid support and monitoring power per wavelength; driving standards and interoperability in terms of optical transmission, open APIs, and standardized YANG data models, and by organizations, including ITU-T, Open ROADM MSA, OpenConfig, Open Networking Foundation (ONF), and Telecom Infra Project (TIP).

Implementation of Open Optical Networks- Requirements

It is the choice of network operators to decide how fast and how far, they want to have transition — from a proprietary network to a fully open architecture — and all points in between -Open Xponders and Open (optical) line systems. To assist with the transition to open, the Open Line System (OLS) and compact modular platforms with a wide range of functions reference architecture to provide a general guideline for constructing disaggregated systems. There are important four points to be discussed for the transition from proprietary to fully open architecture :

Open Xponders provided by any vendor with performance are not dependent on specific optical line system features. It is a highly desirable attribute that Open Xponder should have the ability and capbility to tune the center frequency along with baud rate/spectrum, and modulation of the wavelength.

An open (optical) line system (OLS) should be able to support a wide range of open Xponders supplied by a third party. OLS allows independent selection of ROADM and transponder vendors in a number of configurations in terms of per-channel power monitoring and attenuation for third-party wavelengths, flexible grid support, link control algorithms from any third-party Xponders without affecting performance.

Compact modular platforms have a wide range of functions. They are enabled by self-contained sled-based hardware and with a robust and flexible microservices-based software architecture. It provides footprint, power, and cost benefits and reduces the number of platforms for each vendor. It further speeds up the pace of deployment of new functions and technologies from a particular third-party vendor.

NETCONF, RESTCONF, and gRPC/gNMI APIs are Open APIs and YANG data models which are compliant with Open ROADM and/or OpenConfig, These data models are compatible on compact modular platforms and they in turn support the management and control of multi-vendor optical networks and also multi-layer networks. It facilitates new optical technologies for smooth integration with industry tools for streaming telemetry, analytics, dashboard, automation, and machine learning, etc

Optics for Open Optical Networks

400G OpenZR+ and Digital Coherent Optics (DCO) shall transform conventional data center interconnect, metro, and regional markets, because both 400G OpenZR+ and Digital Coherent Optics (DCO) have been standardized to be inserted directly into any optical, router, and/or switch platform. This plug-and-play or pluggable option did never exist earlier before and this aspect opens the optical networking market for DCO optics and may be deployed ubiquitously based on the standards.

Few options are shown in Fig 3 (ref Cisco blog )This includes the 400G QSFP-DD, which is either the 400G ZR of Optical Internetworking Forum (OIF); or the OpenZR+ supporting Open Reconfigurable Optical Add-Drop Multiplexer (ROADM) on the line side; or the Open ROADM, in CFP2 format.

The barrier to Open Optical Networking Adoption

The operational complexity of dealing with multiple vendors is the paramount barrier to the adoption of open optical networking. Other top barriers are lack of standards and immaturity of the standards which are presently existing. Because of all these barriers, the industry is making efforts into standardizing data models, application programming interfaces (APIs), and different protocols.

Figure 4 above presents barriers to open optical networking adoption in percentage.

Industry Initiatives for Open Optical Networking

The vision and the initiative of Open Optical Networking are quite complex and compelling. If the industry agrees on reference architectures and standard protocols, it leads to modular building blocks for both open optical hardware and open-source Software Defined Networks(SDN). This in turn will attract new vendors and develop and build up a robust open ecosystem. Following are some of the major initiatives in the industries:

Open ROADM: Defines specifications of interoperability for, pluggable optics, transponders, and ROADM. It covers both YANG data models and optical interoperability.

TELECOM INFRA PROJECT(TIP): It works on various sub-projects regarding different parts of the network Open Optical & Packet Transport (OOPT) group

GNPy is an open-source library for building route planning and optimizing the tools for real International multi-vendor optical networks

DOS (Disaggregated Optical Systems) defines and builds open transponders and other disaggregated optical hardware.

CANDI (Converged Architectures for Network Disaggregation & Integration) works on defining and proving service provider use cases in open converged packet/optical networks.

OOPT-NOS (Network Operating Systems ): works on a reference open-source Network Operating System (NOS) and supports disaggregated hardware platforms of OOPT (Open Optical Packet Transport Network ).

ODTN (Open and Disaggregated Transport Network): This is initiated by a service provider for building data center interconnects with the use of disaggregated optical equipment along with open and common standards, and open-source software.

Open Optical and disaggregation networking gives impetus to optical network with enhanced velocity of innovation cycle, economic benefit and evolution as telecommunications industry matures. Such evolution can be seen across a number of areas in networking, including open RAN initiatives for 5G. As per ACG Research Survey report 2021,

A project of the ONF (Open Networking Foundation), OpenConfig: It is a working group of an informal service provider adopting SDN (software-defined networking) principles.

OpenDaylight: This is an Open source SDN controller for customizing and automating optical networks.

Open Network Automation Platform: It is for orchestration, management, and automation of network and edge computing services and virtual network functions.

These initiatives sometimes overlap, though sometimes they have differences in their approach and specific areas of focus. They are associated with the telecom industry and optical networking industry.

Future of Open Optical Networks

The group of open initiatives appears to be sometimes confusing and even sometimes contradictory. Each of them has a different level of openness. They have strengths as well as weaknesses. Ultimately openness in the open optical networks provides cost-effectiveness and opportunity for innovating on one side and value to customers on the other.

The future of Open Optical Networking will have some specific reference network components and a few new technologies such as Opening the ROADM network, Disaggregating the Transponder, Planning with Multi-Vendor Optical Design Tools, Controlling Multi-Vendor Optical Networks, Adding Alien Wavelengths, etc.

Dr. Anuj Kumar Srivastava, Former Executive Director, MTNL, Government of India, Visiting Faculty IIT Delhi, and FMS University of Delhi

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