The right certification program can cure your interoperability woes

The right certification program can cure your interoperability woes

By Franck-Nicolas Sellier, CEO at MT2, and Thierry Doligez, Director at LANPARK

When you consider the Passive Optical Network (PON), you can’t just look at the passive elements – the active elements that build your network must be considered. This includes Optical Line Terminals (OLTs), optical modules, and Optical Network Units (ONUs). The interoperability of the PON is the ability of two active elements, an OLT and a ONU, to work together to bring the intended service and provide Quality of Service (QoS) to the end-user.

We must first take a look at the standards set by the ITU including ITU G.984.x (GPON), G.987.x (XG-PON), G.9807.x (XGS-PON), and G.989.x (NG-PON2), and G.988 (OMCI). Whenever there is wiggle room, you have interpretation from different vendors, and therefore, several behaviors are possible.

If we had to classify the most common interoperability issues from our experience, this would include:

The Physical Layer

• Burst definition (defined by the OLT)
• Rogue ONU (ONU drifting)
• Alien ONU

Service Configuration  

• OMCI (ONT Management Control Interface)
• NETCONF/YANG

Configuration languages are usually complex and offer many services and configuration options, and are therefore prone to configuration issues.

QoS (Quality of Service)

• Packet delivery
• Latency
• Throughput

Who does this concern?  

There is an ecosystem of players around interoperability – you are not alone! Standards bodies including ITU, FSAN and Broadband Forum are using the standards to define and create Conformance and Interoperability Test Plans. Test laboratories, such as LANPARK, have been chosen by Broadband Forum to perform the ONU Certification, thanks to the BBF.247 Test Plan. There have been Interoperability Plugfests organized between ONU and OLT manufacturers. Others will come to support new industry standards and needs.

Test equipment manufacturers, such as MT2, are also involved, where they design, develop and manufacture PON Analyzers to get the protocol messages in real-time between the two active elements to address any issues. An OLT Emulator and ONU Emulator are also developed to test the active elements before any deployments, or any specification is introduced.

Why ensure PON interoperability? 

Interoperability should be considered for the long-term perspective. Service providers are considering the core network from a viewpoint of managing their assets, whereas the vendor is looking more from a business opportunities perspective. For services providers, this reduces the cost of equipment, brings security as you secure the equipment supply of different brands and products, reduces the validation time and integration cycle, and facilitates the equipment, network and services evolution for the future.

The vendor can also reduce the development and test efforts across a range of products, reduce the validation time and integration cycle in line with the operator, expand markets and unlock new business opportunities. But, PON interoperability also brings with it, some challenges, such as the cooperation and willingness between the service provider and the vendor, complex interoperability issues, time to build the operator internal skills, and costs involved with certifying your products and investing in test equipment.

BBF.247 ONU Certification Program  

Launched in 2011, the BBF.247 Certification Program assists the industry with the mass deployment of interoperable GPON solutions. This aids manufacturers and operators’ testing methods specific to each network. BBF.247 guarantees operators that their ONUs selected, comply with the requirements of OMCI based PON standards. This is also the first step of validating a GPON, XG-PON, or XGS-PON ONU.

Industry standards bodies undertake the first two steps of conformance and interoperability, whereas validation and integration are an operator specific process. This will help ensure that the product is interoperable with the equipment deployed by the vendor and that its behavior and performance in the network are compatible the operator’s requirements. This is a widely adopted Certification Program that is growing over time to support different types of ONUs from Single User port ONUs, to Residential Gateways, to PON-fed Gfast Distribution Point Units (DPU). The last major evolution of this program was the launch of TP-247 Issue 4 last year when new profiles including enhanced services, capacity monitoring and OMCI features were introduced.

So far, 40 companies have already certified their products, with 112 GPON and 21 XGS-PON ONUs being BBF.247 certified. Currently, 20 to 30 ONUs are certified each year, following various tenders and new deployments from operators worldwide. Widely adopted by many network operators and manufacturers, it guarantees the maturity of products proposed by manufacturers, reduces the interoperability, validation, and integration efforts, and therefore, the time-to-market of products. This also facilitates the maintenance of the network and development of new services and technologies.

The test tools are fully automated to facilitate multiple pre-certification test runs. During pre-test, the manufacturer can benefit from diagnostic tools to help identify and fix implementation bugs very quickly. As BBF.247 is well known and mastered by key players in the industry such as chip, OLT and ONU manufacturers, and test labs, new perspectives can be offered to operators seeking to deploy multi-vendor PON networks.

What’s next?

The program continues to evolve and follows operator requirements, architecture, services and technology, and in future, will cater to the future GPON standards, such as, NG-PON2 and HS-PON. Work continues within the Broadband Forum to standardize the management of the PON OLTs, Netconf protocol and YANG data models to ease the management of FTTH architecture and the conditions of the required service to each user.

Download the recording of the latest PON Interoperability and Certification webinar. This offered point of views from an approved test laboratory, test equipment manufacturer, service provider and vendor discussing PON interoperability and BBF.247 Certification in more detail. Download it in full here.