XGSPON/GPON COMBO SFP-DD OLT丨C-LIGHT

XGSPON/GPON COMBO SFP-DD OLT is a highly integrated optical module used in Fiber-to-the-Home (FTTH) access networks. Its key feature is the integration of two distinct optical transceiver systems within a single module. This design allows network operators to smoothly upgrade from traditional GPON networks to higher-speed XGS-PON networks without the need to replace existing fiber cabling or central office equipment.

To clearly understand the technologies it combines and the rationale behind it, refer to the following comparison:

Feature	GPON (Legacy Mainstream)	XG-PON (10G Asymmetric)	XGS-PON (10G Symmetric)
Downstream Rate	2.5 Gbps	10 Gbps	10 Gbps
Upstream Rate	1.25 Gbps	2.5 Gbps	10 Gbps
Key Characteristic	Widely deployed, cost-effective	High downstream, lower upstream bandwidth	Symmetric upstream, downstream bandwidth
Downstream Wavelength	1490 nm	1577 nm	1577 nm
Upstream Wavelength	1310 nm	1270 nm	1270 nm

How the Combo Solution Works

Since GPON and XG(S)-PON operate on entirely different wavelengths, traditional upgrade paths require adding separate modules and external wavelength multiplexing equipment, which is complex. The core innovation of the Combo module lies in:

Integrated Internal WDM Mux/Demux: It acts like a "traffic controller," combining and separating the upstream/downstream optical signals for GPON (1490/1310 nm) and XGS-PON (1577/1270 nm) internally within the module.

Support for Multi-Generation Coexistence: This allows operators to simply replace a single module at the central office OLT. Over the same existing fiber, they can simultaneously serve legacy customers with GPON Optical Network Terminals (ONTs) and new customers with XGS-PON ONTs, enabling a seamless, non-service-disruptive upgrade.

Advantages of the SFP-DD Form Factor

"SFP-DD" refers to the physical form factor of this module. Compared to the previously common "SFP+" Combo modules, its main advantages are:

Compact Size, Doubled Density: The SFP-DD interface has the same physical dimensions as a traditional SFP+ module. However, by supporting dual-channel data transmission, it enables significantly higher port density on equipment line cards. This means a single chassis can support more subscriber connections.

Future-Proof Design: This form factor is designed for higher future speeds (e.g., 25G, 50G and beyond). Choosing an SFP-DD Combo OLT module also lays the hardware groundwork for future evolution to next-generation PON technologies (like 50G PON).

Core Value and Applications

In summary, the core value of the XGSPON/GPON COMBO SFP-DD OLT lies in "smooth evolution" and "investment protection."

For Network Operators: It eliminates the need to overhaul the deployed Optical Distribution Network (ODN), protecting existing infrastructure investments. Upgrades can be performed gradually as subscriber demand grows, drastically reducing the cost and complexity of network evolution.

Typical Specifications: Current market modules typically support a 20 km transmission reach, are available in commercial and extended industrial temperature ranges (e.g., -40°C to 85°C), and generally consume less than 3 watts of power.

Application Scenario: It is primarily deployed in operator central offices or street cabinet OLT equipment, serving as a key central-site device enabling Gigabit and 10-Gigabit fiber broadband access.