As XGS-PON deployments continue to expand, interoperability between optical line terminals (OLTs) and optical network units (ONUs) becomes increasingly important. At CableLabs’ June XGS-PON Interop·Labs event, suppliers exercised new capabilities introduced in a pre-release of the Cable OpenOMCI I04 specification. The work helped validate implementations and identify opportunities for further refinement.
In preparation for the event, participating suppliers worked with CableLabs to update the interop test plan to reflect the requirements in the forthcoming Cable OpenOMCI I04 specification.
The updated test plan introduced several new validation scenarios intended to confirm consistent implementation of new requirements, and to better exercise configuration and performance monitoring scenarios typical in network operator deployments.
The June XGS-PON Interop·Labs Event
Testing during the event — held in our labs in the Louisville, Colorado, headquarters — focused on ONU Management and Control Interface (OMCI), defined in the ITU-T Recommendation G.988 and the CableLabs Cable OpenOMCI specification.
During the event, OLT and ONU equipment from different suppliers were paired together to validate a wide range of service configuration and monitoring scenarios. Supplier engineering teams arrived with updated software builds and new device variants. The set of suppliers grew to include two OLT suppliers and two ONU suppliers who were participating in their very first CableLabs XGS-PON interop event.
Supplier Participation in the XGS-PON Interop
We appreciate the participation of the suppliers who took part in the June event. Participating suppliers brought a diverse set of XGS-PON equipment, including both OLTs and ONUs representing multiple device architectures and chipset families. The participating OLT platforms were Adtran’s SDX 6312-4, Calix’s E7-2, Ciena‘s uOLT (represented by RocNet) and Nokia‘s Lightspan MF-2.
These OLT systems were paired with a broad set of ONUs and PON residential gateways. Participating ONU suppliers that sent U.S.-based engineers were Adtran, Calix, Hitron, Nokia, RocNet, Sagemcom, Tinno and TP-Link.
The diversity of participating devices created a wide range of multi-supplier combinations, enabling engineers to exercise how different implementations behaved across numerous ONU-to-OLT pairings.
Some suppliers brought multiple ONU models. In total, participants exercised 34 unique test pairings during the week.
Testing Environment & Themes
The interop environment allows engineers to directly observe how their implementations behave when paired with equipment from other suppliers. These multi-supplier pairings often reveal subtle differences in OMCI behavior that may not be apparent during testing in the supplier’s own facility.
During the event, each OLT supplier operated a dedicated lab setup that included a small-scale PON optical distribution network connecting the OLT platform to one or more ONUs under test. Engineers relied on OLT debugging tools and an XGS-PON analyzer, provided by CableLabs, to capture OMCI message exchanges and traffic behavior during each scenario.
During the week of testing, engineers focused on several new requirements introduced in the Cable OpenOMCI I04 specification:
- Media Access Control (MAC) Learning and Limiting on ONU user-network interface (UNI): The purpose of this test case is to exercise the dynamic MAC learning capacity of the ONU and OLT. This test verifies that the ONU can properly implement customer premises equipment (CPE) MAC address learning and limiting capabilities and properly forward traffic for those learned CPE MACs.
- Extended virtual local area network (VLAN) tagging operations configuration data — Downstream mode 6: The purpose of this test case is to verify the ONU properly handles the Downstream mode 6 option of the Extended VLAN tagging operations configuration data feature. This test verifies that the ONU can properly forward downstream frames bearing an unexpected Priority Code Point (PCP) value, such as is often seen on Address Resolution Protocol (ARP) Response packets.
These scenarios were designed to expose differences in device behavior, enabling engineers to isolate root causes and translate those findings into improvements in both specifications and implementations.
Results from the event showed that many suppliers had improved in areas that had been identified during earlier interoperability events, while the expanded test coverage also uncovered additional behaviors that will guide future development and testing.
The Testing Continues
We follow an iterative process of lab validation, specification updates, and OLT and ONU software updates with each interop event cycle to achieve continuous improvement in cross-vendor interoperability. Ensuring interoperability of hardware provides network operators with greater choice in selecting the devices to deploy on their networks.
Our next PON interop event is scheduled for October 2026, when we’ll continue exercising the requirements defined in the Cable OpenOMCI I04 specification.
We look forward to welcoming suppliers back to our Louisville lab as this work continues.
