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Why Do PON Modules Use SC Connectors?

LarryUpdated at Feb 5th 20251 min read

In fiber optic communications, the interface type of an optical module significantly impacts signal stability and reliability. The table below outlines the key specifications of select FS PON modules.
Model
Access Technology
Data Rate
Interface
Class
Power Consumption
GPON
2.5G-TX/1.25G-RX
SC
B+
<1.5W
XGPON
2.5G-TX/10G-RX
SC
N2
<1.5W
XGSPON
10G-TX/10G-RX
SC
N2
<2W
XGS-PON&GPON Combo
10G-TX/10G-RX
2.5G-TX/1.25G-RX
SC
C+
<3W
EPON
1.25G-TX/1.25G-RX
SC
PX20+
<1.5W
10G EPON
10G-TX/10G-RX
SC
PR30
≤2W
We can notice a consistent pattern: whether examining GPON, EPON, or XGS-PON modules, their optical interfaces almost universally use SC connectors instead of LC connectors. This article explores why SC connectors prevail in PON modules through three critical factors: interface characteristics, PON networks requirement, and industry standard.
SC vs LC Connectors: Key Differences Explained
SC (Subscriber Connector) and LC (Lucent Connector) are two of the most widely used fiber optic connectors, each offering distinct advantages.
The SC connector has a square design and a larger form factor, featuring a push-pull locking mechanism for a secure connection. In contrast, the LC connector is much more compact—about half the size of an SC connector—and utilizes a latch mechanism to optimize space efficiency.
SC connectors are highly precise and sensitive to return loss, making them ideal for applications where signal quality is crucial. LC connectors are compact and support high-density connections, typically used in pairs.
Feature
SC Connector
LC Connector
Size
Larger (2.5mm)
Smaller (1.25mm)
Density
Lower
Higher
Insertion Loss
<0.3dB
<0.2dB
Typical Use
PON, FTTH
Data Centers
Why Do PON Modules Use SC Connectors Instead of LC
Industry Standards
SC connectors are widely supported by industry standards such as ITU-T G.984 (GPON) and IEEE 802.3ah (EPON). These standards recommend the use of SC connectors, establishing a consensus within the industry. This standardization ensures full-link compatibility from PON transceivers, OLTs, and splitters to ONUs, reducing coordination costs between equipment manufacturers and operators.
Cost Advantages
In the context of large-scale network deployments and massive user access, PON networks are highly cost-sensitive. SC connectors offer lower manufacturing costs compared to LC connectors and feature a simple plug-and-play design, making them easy to install and maintain. This makes them a more cost-effective choice for large-scale PON networks deployment.
Demand for Bidirectional Transmission
The bidirectional data transmission method used in PON networks significantly impacts the module interfaces. This approach enables BiDi transmission by using different wavelengths of signal within a single fiber. Such a transmission method requires interface designs that accommodate this characteristic. The SC interface, with its larger head structure, effectively houses the optical components necessary for BiDi transmission, thus enhancing signal reliability.
Why PON Adopts a Bidirectional Transmission System
The key advantage of a single-fiber bidirectional system lies in its cost efficiency, particularly in last-mile FTTH deployments.
In contrast, a dual-fiber bidirectional system requires each PON port to be equipped with two separate fibers—one for upstream and one for downstream transmission. As illustrated, dual-fiber systems demand twice the fiber resources, splitters, and cabling space compared to single-fiber systems, significantly driving up the overall deployment cost of the optical distribution network (ODN). For large-scale PON deployments, such a high-cost cabling approach is neither economically viable nor scalable.
Another critical challenge in dual-fiber systems lies in their complex physical connectivity. In a dual-fiber bidirectional system, the transmit (Tx) port of the sending device must be connected to the receive (Rx) port of the receiving device, while the Rx port of the sending device needs to link to the Tx port of the receiving device. This strict connection requirement often leads to fiber misalignment during deployment, commonly referred to as "crossed fiber" or "miswiring." Such errors can cause communication failures and significantly increase the complexity of installation, as well as drive up long-term maintenance costs.
In contrast, a single-fiber bidirectional system leverages wavelength-division multiplexing (WDM) technology to isolate upstream and downstream signals by wavelength, effectively eliminating the risk of physical connection polarity errors. This approach not only simplifies the installation process but also reduces operational complexity, making it a more efficient and reliable solution.
Conclusion
In summary, the widespread adoption of SC connectors in PON modules is driven by their alignment with industry standards, cost efficiency, and compatibility with bidirectional transmission requirements. These factors, combined with the inherent advantages of single-fiber bidirectional systems—such as reduced deployment costs, simplified installation, and enhanced reliability—make SC connectors the optimal choice for PON networks.
Interested in learning more about PON modules and other PON devices? Explore our product offerings at FS.com