There has been momentum in the broadband industry to provide fiber to the premises (FTTP) solutions as a part of an operator’s service portfolio. While optical technologies have long been a part of the cable network, FTTP is the chosen architecture for all-fiber access networks.

For FTTP, the premises can be a subscriber’s home, a commercial location, a campus environment, a multi-dwelling unit (MDU) or another location. Over the past couple of decades, operators have embraced the passive optical network (PON) technology for their fiber-based access network implementations. The point-to-multipoint topology of PON lends itself nicely to the current and future designs of the broadband network.

More recently, many operators have begun deploying PON technologies defined by the International Telecommunications Union Telecommunications Standardization (ITU-T). As a part of its standards development, ITU-T has released standards for 10 Gigabit Symmetrical PON (XGS-PON).

With broadband operators beginning to deploy multiple gigabit service, there’s a growing current of enthusiasm and interest for the efficient deployment, management and maintenance of those access networks. Furthermore, the speed at which technology is moving is impressive and expensive. It is challenging to keep pace with these advancements, which require a matrix of expertise and decision-making support.

Building on PON’s Momentum

PON is one of the technologies that keeps marching forward. CableLabs has participated in the development of PON-based standards and specifications for over a decade, and we’re continuing in that vein to help operators lower barriers for deploying and operating FTTP solutions.

Common provisioning and management of PON in the broadband industry typically requires support of legacy systems that have been in place for decades, e.g., DOCSIS® operations support system (OSS) or integration with newer back-office systems. Near-term objectives for the work CableLabs is beginning include XGS-PON and 25GS-PON support, covering applicability for next-gen PON flavors with special focus on vendor neutrality through device interoperability.

CableLabs has created two working groups dedicated to optimizing the integration of ITU-T PON technologies into cable networks. The two working groups are the Common Provisioning and Management of PON (CPMP) and Optical Operations and Maintenance (OOM). These two groups are complementary in their activities. The CPMP group is focused on supporting the back-office provisioning and management of XGS-PON as well as the interoperability of optical network units (ONUs) with optical line terminals (OLTs). The OOM working group is focused on the operations and maintenance of the underlying optical networks.

Hurdles in Interoperability

There are always tradeoffs with technology, whether it’s price, timing or things out of an operator’s control, such as product availability. However, when customer premises equipment (CPE) is required, there is always an underlying benefit to the interoperability of that device with the network that it connects to.

Interoperability provides necessary competition, which results in pricing benefits, innovation and choice for operators. Having the choice of which ONU is connected to the OLT is instrumental in providing lower cost services with the ability to help foster innovation.

Interoperability involves several technical and logistical challenges. Addressing these hurdles typically involves a combination of adherence to standards, thorough testing and collaboration between vendors to ensure equipment from different manufacturers can work together seamlessly. These hurdles to interoperability include:

• Standardized technology: Standards are not necessarily the end-all-be-all for successful interoperability. In the context of XGS-PON, there is the ONU Management and Configuration Interface (OMCI). This OMCI information is defined in the ITU-T G.988 standard. This is the accepted way to configure and manage ONU equipment via the OLT. OMCI is extremely comprehensive and as such, it is very difficult to provide simple and extensible ways to support interoperability.
• Vendor-specific implementations: Vendors may support proprietary features or extensions in their products. While these can offer enhanced performance, additional functionality and vendor differentiation, they can also create interoperability issues if these features are not supported universally across different vendor equipment.
• Operator requirements: Each operator deployment is different, and each operator requires a specific implementation to support their business objectives. While certain configuration parameters, fault reporting and performance monitoring are common among different implementations, there are always variations, and this requires different configurations for network components and CPE.
• Network configuration, service activation, and management: XGS-PON networks require precise network management and configuration to ensure proper operation. Differences in management systems and configuration approaches between vendors can create integration challenges.
• Testing and certification: Comprehensive testing is required to ensure that equipment from different vendors works together as expected. Many operators and vendors don’t have the infrastructure to support such testing, which becomes a barrier when choosing equipment suppliers. A significant impact on time-to-market is testing. Testing and validation of requirements is a significant cost and effort.

Mitigating Interoperability Hurdles

CableLabs, with the support from vendor partners and member operators, has long had a successful formula for developing specifications that have transferred to CPE interoperability. Device interoperability is the primary objective when producing interface specifications between network components. Vendor neutrality through that device interoperability is a key intention for operators deploying XGS-PON in cable networks.

Developing documentation to standardize technology with the intent for interoperability is a fine line to walk when working with multiple operators and equipment manufacturers. To add fuel to the fire, when standards have already been written, developing a method for interoperability can require modifications to the original formula. By leveraging the existing G.988 OMCI standard, CableLabs is developing a Cable OpenOMCI specification to support ONU configuration in an interoperable way within the industry.

While it is always a goal to develop common processes and requirements that encourage the vendor ecosystem, sometimes vendor-specific parameters are required to support vendor differentiation. It’s important for vendors to differentiate their products, which provides their teams to innovate. The work CableLabs is doing to support device interoperability includes the ability for vendor-specific configurations when needed.

Each operator is different, and each operator has its own set of business objectives that translates to the products it buys, the services it offers, and the networks it builds. When developing specifications to support a myriad of operator requirements that span the globe, we must always be cognizant on ways to support those requirements. During our specification development we work together to identify and accommodate those differences needs across the industry.

While each network is different, for interoperability, some network configuration, service activation, and management must be standardized. This can be required anywhere in the network from the back office all the way to the end of the network with CPE. When building a program to support interoperability this entire ecosystem is in play. The coordination effort and the development of a common set of processes to support interoperability with device configuration, service activation and management is key.

In February, we hosted a DOCSIS® Provisioning of XGS-PON Interop·Labs event for members of the CPMP working group. Testing and certifying devices are very important for interoperability. To help remove the barriers of cost and reduce time-to market with comprehensive testing, CableLabs provides formal interoperability events like this as well as ongoing interoperability activities. Additionally, if needed, CableLabs will develop a certification program to test and certify ONUs against the specification.

Pushing Toward XGS-PON Adoption

While XGS-PON is gaining interest with cable operators, the industry is keen to develop procedures and specifications to support ONU interoperability with OLTs. While there are always common hurdles to interoperability, they are never enough to stop interoperability. Since the XGS-PON technology has already been defined and standardized by ITU-T, this does bring a different hurdle to the work.

Typically, CableLabs and its vendor partners and member operators develop the specifications that support interoperability. However, in this instance, we must leverage existing standards from another SDO. It won’t be impossible, but it will be a heavy lift.

Learn more about our working groups and how CableLabs members and our vendor community can help us chart the way forward for technologies like this.