GPON SFP Transceivers in Detailed Introduction
GPON refers to the Gigabit Passive Optical Network. It is standardized by ITU-T G.984, which is the major technology for implementing optical fiber-based broadband access networks with P2MP topology. A typical Gigabit PON network is comprised of Optical Line Termination (OLT) in the central office and Optical Network Termination (ONT) or Optical Network Unit (ONU) at the client premises equipment. In the GPON architecture, components are mainly passive. GPON SFPs are the optical transceivers used in the OLT and ONT/ONU to achieve GPON triple-play services.
What is GPON SFP?
GPON SFP refers to the Gigabit Passive Optical Network Small Form-factor Pluggable module, complying with ITU-T G.984.2 standards. Gigabit PON SFP is a type of BiDi SFP designed for the GPON system. It has a bidirectional channel using different wavelengths to transmit and receive signals between the OLT central office and the customers’ side over a single fiber.
GPON SFP Classification
GPON OLT SFP vs. GPON ONT/ONU SFP
GPON SFPs deployed in the OLT central office side are GPON OLT SFP modules and applied in the ONT/ONU on the end users’ side are GPON ONT SFP or GPON ONU SFP modules.
GPON OLT SFP provides OLT in the service provider’s central office the interface to access the optical fiber network for transmitting and receiving triple-play traffic (data, voice, or video traffic). Simultaneously it connects to multiple ONTs/ONUs on the subscribers’ side, therefore OLT GPON SFP masters the traffic control both upstream and downstream. The SFP gigabit PON OLT transceivers provide the data rate of 2.5G-TX/1.25G-RX up to 20km over SMF at 1490nm-TX/1310nm-RX.
GPON ONT SFP offers ONT/ONU in the client end sides of the interface to talk with end devices over the optical fiber network. With the ONT GPON SFPs, the triple-play services are delivered to switches, routers, computers, phones, or other end devices for residential or business usage. GPON ONT SFPs is a plug-and-play solution for ISP to provide multiple terminals to obtain optical fiber-based services. GPON SFP ONU stick provides 1.25G upstream and 2.5G downstream and supports up to 20km over SMF.
SFP GPON C++ vs. SFP GPON C+ vs. SFP GPON B+
Depending on the standard class, GPON SFPs can be classified into class B+, class C+, and class C++. What defines the difference is the transmission parameter, such as the Tx power and Rx sensitivity. The following table lists the main differences between SFP GPON C++ vs. SFP GPON C+ vs. SFP GPON class B+.
Different classes of OLT GPON SFP also differentiate in the capacity of supported ONTs. Some providers specified the OLT GPON SFP class C+ can support up to 64 ONTs/ONUs while GPON SFP class B+ supports 32 ONTs/ONUs.
GPON SFP vs. Common BiDi SFP Differences
Though the GPON SFP module belongs to bi-directional SFP. However, GPON SFP is quite different from the regular BiDi SFP transceivers.
Connector
In the market, BiDi SFP transceivers are available for LC connectors or SC connectors. GPON transceivers are usually seen as SC connectors.
Transmission Distance
Regular BiDi SFP transceiver can reach up to 160km at the wavelength of 1490nm-Tx/1550nm-Rx and 1550nm-Tx/1490nm-Rx over single-mode fiber (SMF) with LC simplex connector. However, limited by signal strength, it is generally recommended to use OLT GPON SFP within 20km using 1490nm-Tx/1310nm-Rx. (Note: the maximum transmission distance may be distinct from vendor to vendor. For instance, HW claims the MA5671A has an optical reach of up to 30km)
Topology
Traditional BiDi SFP transceivers utilize point-to-point (P2P) signal transmission mode, which means two BiDi SFPs with opposite TX and RX wavelengths are used symmetrically in pairs at two ends. GPON modules are applied for point-to-multiple-point (P2MP) applications. In the central office, OLP plugged with an OLP GPON SFP is connected to a fiber optic splitter over a single fiber, and the optical splitter will linked to multiple ONUs on the other side.
GPON SFP Advantages
Cost-Efficiency
GPON SFP solution is energy-saving since it is applied in passive systems. GPON architecture requires a little energy for operation. Also, as a technology to direct connect the internet service provider’s optical fiber services to multiple clients with the help of a fiber optic splitter, the GPON system requires less equipment (Before the SFP GPON module has been published, at least one optical modem and IP router should be installed in the ISP). Besides, the GPON transceiver maximizes fiber resources by using bidirectional and wavelength division multiplexing (WDM) techniques. Green energy, simplicity in architecture, and fiber efficiency make GPON SFP a simple and cost-efficient solution.
Triple-Play Services
The GPON SFP also has the advantage of triple-play services integration, allowing ISP to provide customers with a bundled internet, voice, and video service through a single fiber connection. However, before GPON SFP is released, additional equipment needs to be added if video or voice services are required.
Symmetrical Upload and Download Speed
With a P2MP topology, GPON supports delivering the upload stream and the download stream at a symmetrical speed. This feature is beneficial for application-critical to both download and upload data, such as video recording, shared disk, and other cloud services.
GPON SFP Application FTTP (Fiber-To-The-Premises)
Gigabit PON SFP supports any FTTx deployment scenarios, including Fiber to the Home (FTTH), Fiber to the building (FTTB), Fiber to the curb (FTTC), Fiber to the cell (FTTc), and Fiber To The Business (FTTb). Given that FTTx is the popular fiber-based access to high-speed broadband service, GPON SFP transceivers are widely applied in residential, business, or Multi-Dwelling Units (MDU) areas. With a triple-play mode, the users can enjoy high-bandwidth internet service, voice communication, and HD videos.
Summary
GPON SFP is a small pluggable module used in the passive optical network system for FTTx applications. GPON OLT SFP and GPON ONT SFP/GPON ONU SFP are two types of gigabit PON SFPs based on the deployment devices. SFP GPON C++, C+, and SFP GPON B+ are different from specification indexes, such as optical power and receiver sensitivity. As a bi-directional optical module, the GPON SFP module differs from conventional BiDi SFP in popular connector type (SC vs LC), transmission distance (20km vs 160km), and application topology (P2MP vs P2P). GPON SFP solution provides a cost-efficient, simple-deployment, and highly service-integrated technique for high-bandwidth optical fiber-based services.
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