Fiber Network Comparison: GPON vs XGPON vs WDM PON Examining Advanced Technologies

PON Evolution is pivotal for the telecom industry. GPON, XGPON, and WDM PON networks offer diverse applications, enhancing bandwidth, service support, and performance of access nodes. This post delves into the distinctions among GPON, XGPON and WDM PON.

Overview of GPON, XGPON and WDM PON

GPON or Gigabit Passive Optical Network, is a broadband access technology that utilizes optical fiber for high-speed, bidirectional data transmission. It operates on a point-to-multipoint basis with passive splitters in the fiber distribution network, enabling a single fiber from the service provider's central office to serve multiple homes and small businesses. GPON is widely adopted for its cost-effective deployment of high-bandwidth services, including broadband internet, IP telephony, and digital television.

XGPON or 10G-PON, represents an advancement over GPON, introducing a migration mechanism for a 10 Gbits downstream signal and a 2.5 Gbits upstream signal. In XG-PON, the downstream signal for users is defined within the range of 1575nm to 1580nm, while the upstream signal operates from 1260nm to 1280nm. This technology retains the point-to-multipoint (P2MP) architecture of GPON and accommodates various access scenarios, including fiber to the home (FTTH), fiber to the cell (FTT Cell), fiber to the building (FTTB), fiber to the curb (FTT Curb), and fiber to the cabinet (FTT Cabinet).

WDM-PON or Wavelength Division Multiplexing Passive Optical Network, is an access network technology with transformative potential for carrier infrastructures. It establishes a wavelength-based logical point-to-point architecture on a physical point-to-multipoint fiber topology. Utilizing WDM multiplexing/demultiplexing technology, WDM PON divides data signals into individual outgoing signals connected to buildings or homes. This hardware-based traffic separation offers customers the advantages of a secure and scalable point-to-point wavelength link, while allowing carriers to maintain minimal fiber counts, resulting in significantly reduced operating costs. In today's networks, WDM PON also plays a crucial role in 5G fronthaul infrastructure.

GPON vs XGPON vs WDM PON

Here we have summarized the technical performance of GPON,10G-PON and WDM PON in the table below. And more details will be discussed in the following texts.

GPON vs XGPON

The distinction between GPON and XGPON lies in their transmission speeds and wavelength utilization. GPON operates at standard gigabit speeds for both upstream and downstream communication, while XGPON sets itself apart by introducing a 10 Gbps downstream, significantly elevating data transfer rates. Furthermore, GPON relies on fixed wavelengths for both upstream and downstream channels, whereas XGPON optimizes performance by employing different wavelengths for each direction. Both technologies, however, offer seamless coexistence within the same network infrastructure. XGPON's notable flexibility provides an upgrade path from GPON, enabling operators to enhance speeds without necessitating a complete network overhaul. This comparison underscores how XGPON extends capabilities beyond GPON, making it a strategic choice for network evolution.

GPON vs WDM PON

The disparities between GPON and WDM PON primarily revolve around capacity and fiber utilization. WDM-PON's user capacity is straightforward, with one dedicated wavelength per end-user, typically transmitting a GbE signal at 1.25 Gbps. However, in scenarios with pure broadcast signals (e.g., conventional IP-TV), WDM PON doesn't hold a particular advantage, as the broadcast signal must be replicated for each wavelength and independently sent to users.

In contrast, evaluating GPON capacity per user is more complex, hinging on the bundle of services offered and considering various elements. GPON's bidirectional transmission, compared to WDM PON's unidirectional transmission in our example, results in more efficient fiber utilization for GPON. Although WDM PON can utilize unidirectional transmission, it comes with its associated costs.

WDM PON vs XGPON

The optical link budget presents a significant contrast between WDM PON and XGPON. In WDM PON, the transmission scheme is relatively straightforward, with attenuation determined by the MUX/DeMUX loss and fiber propagation, accounting for connectors and other signal-diminishing elements in the access infrastructure. For instance, in CWDM PON, standard optics can ensure a transmitted power of 0 dBm, and the receiver sensitivity, based on the detector used (e.g., PIN), might be around -18 dBm at 1.25 Gbps (assuming GbE transmission).

In contrast, XG PON, specifically XGPON1 standardization, mandates a link budget sufficient for a reach comparable to GPON B+ and GPON C. Considering the slightly higher losses experienced by XGPON1 wavelengths and other differences in the transmission line between GPON and XGPON, the link budget is set at 29 and 31 dB, depending on the comparison with GPON B+ or GPON C.

On the OLT side, XGPON, utilizing shared OLT ports, offers advantages in power consumption compared to WDM PON, which requires a dedicated OLT port per subscriber. However, WDM-PON, with typically lower power budget due to reduced losses from the splitter, may have lower power consumption per transmitter. Integration (Tx, Rx arrays) and the ability to turn off unused OLT ports further contribute to WDM-PON's power-saving capabilities. On the ONT side, XGPON benefits from not requiring cooled lasers, while WDM PON can leverage lower speed and lower power budget components.

Concluding Remarks

In the realm of optical networks, GPON (Gigabit Passive Optical Network) offers advantages such as gigabit-level high-speed connectivity, low latency, high energy efficiency, robust reliability, and cost-effectiveness, making it suitable for diverse application scenarios. XGPON (10G Passive Optical Network) achieves breakthroughs in higher transmission speeds, flexibility, and advanced technical standards, safeguarding network operators' investments through a seamless upgrade path. WDM PON (Wavelength Division Multiplexing Passive Optical Network) utilizes wavelength division multiplexing technology to enhance network capacity and deliver personalized services, reducing signal transmission losses and improving overall network efficiency. The choice of technology depends on specific network requirements and the strategic goals of the operator.