Over the last 70 years, telecommunications operators and manufacturers have continued to develop open standards for “wireline” carrier networks which began with copper technologies and by the early 2010s, fiber, specifically Passive Optical Networks or PON. Operators and their solutions partners created organizations focused on standards-based technologies, first with ADSL and then VDSL -- along with G.hn -- which provided technical flexibility and greater market options regarding the type of CPE that would be deployed. With PON, the ITU-T has led the requirements of the standards with this technology since the early 2000s.
Early PON Technologies
Standards groups in the early 2000s and their members had to resolve multiple network requirements from management to diagnostics against available silicon technologies and the evolution of fiber bandwidth. Add additional factors such as security, optimizing the number of customers per port, and other factors. The first result of this collaboration was G.983 which was published by the ITU-T in 2003 and defined BPON networks. The first GPON standard, G.984, was released in 2008 to include changes such as the removal of ATM requirements in the specification.
The most critical function of the ITU-T PON standard was the ONU Management and Control Interface or OMCI, which became the foundation for GPON and XGS-PON networks deployed globally.
One issue not resolved by early ITU standards was vendor interoperability. Unlike existing VDSL networks, for example, initial PON central office and CPE products were based on a closed architecture limiting networks to a single solution at both “ends” of the fiber strand.
OMCI: The Key to PON Functionality…and Open Standards
The ITU-T OMCI standard is a messaging format and management “mechanism” used by the OLT (Optical Line Terminal) to perform multiple functions with the end user’s CPE or ONT (Optical Network Terminal) deployed throughout a carrier’s network. The OMCI protocol messages are transported over fiber via the OMCC (ONU Management and Control Channel) and are encapsulated in the OMCI’s GEM (GPON Encapsulation Method) frame. The OMCI provides multiple key management functions within a GPON or XGS-PON deployment including:
- Configuration
- Fault management
- Performance management
- Security management
By 2010, operators and members of the ITU-T began to recognize the importance of establishing an open standard for the OMCI protocol. Unlike xDSL networks or other technologies, PON had very limited opportunities for interoperability since there was no open standard that restricted the solutions operators could deploy in their networks. And, if faced with supply chain issues – shortage of a certain SOC, for example -- the only options available would be waiting for the resolution of the delay or starting over with a new vendor which would also cause delays.
Open OMCI: G.988
This “closed” OMCI issue was addressed by the ITU-T’s G.988 publication in 2010, created with the goal of creating PON interoperability via Open OMCI standards. Open OMCI would allow carriers to select products that best fit their markets, their CAPEX target, or their technology goals. For example, an XGS-PON ONT bridge could be the best fit for an operator’s SMB customers while matching Wi-Fi Routers to the end user’s particular needs. Another example could include the use of a high-end multi-service Gateway in a home where one or more residents may be working remotely and need a 5G LAN or 4+4+4 Wi-Fi coverage while another home may only need a Gateway for streaming and gaming.
Open OMCI, therefore, allows operators the ability to ‘pick and choose the best fit without being restricted to a proprietary architecture and a limited set of CPE technologies. Operators can also switch, when needed, to other devices in case of supply chain disruptions or other events, as noted previously.
Zyxel has, for over a decade, been a leading contributor to G.988 and provided ONTs that are interoperable with over 15 different manufacturers’ OLTs. These ONTs are deployed in networks throughout the globe and provide options such as:
- Full Bridge Mode
- Bridge + VoIP Ports
- Multi-Service Gateways with multiple features such as Wi-Fi, VoIP, Ethernet LAN, and USB.
For over 12 years, Zyxel has provided high-quality/high-performance fiber products that have been deployed by Tier 1, 2, and 3 operators throughout the world. Continuing this tradition, Zyxel’s newest and upcoming XGS-PON products will offer operators options such as Wi-Fi 7 and 5 and 10G LAN. For proven, high-quality, versatile optical technologies that will meet your customer’s network demands, Zyxel Communications is your supplier of PON technologies.