Fiber optic patch cords are essential components of fiber optic communication systems, connecting various devices in the network. The performance of fiber optic patch cords significantly affects network transmission quality. UPC (Ultra Physical Contact) and APC (Angled Physical Contact) are two popular fiber patch cord termination options. There are substantial variances in end surface cleaning processes, insertion loss, return loss, and application conditions.
Basic definitions and differences between UPC and APC fiber optic patch cords
UPC fiber optic patch cords
Definition: UPC (Ultra Physical Contact) optical fiber jumper means that the end face of the optical fiber connector has been ultra-precision polished to make the optical fiber end face appear smooth and flat. The UPC end face is still a slightly curvature spherical surface microscopically, allowing the fiber core to be in closer contact and reducing the air gap.
End face characteristics: The end face of the UPC fiber optic connector presents a smooth curved surface. When docked with another UPC connector, the two end faces can achieve extremely precise physical contact, thereby reducing the reflection and loss of optical signals.
Color identification: UPC fiber optic patch cords usually use blue connectors to distinguish them.
APC optical fiber jumper
Definition: APC (Angled Physical Contact) optical fiber jumper means that the end face of the optical fiber connector is polished at an 8-degree angle. Because of this tilt angle, the reflected light does not return along the fiber but is reflected at an angle away from the incident path, thereby reducing reflection noise within the fiber.
End face characteristics: The end face of the APC fiber optic connector has an inclined angle, making the reflectivity of the optical signal extremely low. This design can effectively reduce return loss when mated with another APC connector, making it perform well in high-performance fiber optic networks.
Color identification: APC fiber optic patch cords usually use green connectors to distinguish them.
Comparison of insertion loss and return loss
Insertion Loss
Definition and Importance: Insertion loss refers to the power loss of an optical signal when it passes through a fiber patch cord or connector, usually expressed in decibels (dB). The lower the insertion loss, the higher the transmission efficiency of the fiber optic patch cord.
Insertion loss of UPC: The insertion loss of UPC fiber optic patch cords is usually lower because the precision polishing of its end faces ensures good fiber docking, but compared with APC, the difference in insertion loss between the two is not big.
APC’s Insertion Loss: APC fiber optic patch cords also have very low insertion loss and perform well in high-density connections and long-distance transmissions.
Return Loss
Definition and importance: Return loss refers to the proportion of optical power of the optical signal reflected back to the optical fiber at the end face of the optical fiber connector, usually in decibels (dB). The higher the return loss, the less reflection of the optical signal, which is particularly important for high-precision and high-stability optical fiber communication systems.
Return Loss of UPC: The return loss of UPC fiber optic patch cords is typically between -50dB and -55dB, which means it reflects less light, but may not be ideal in some high-precision applications.
APC’s return loss: The return loss of APC fiber optic patch cords is usually between -60dB and -70dB. The extremely low return loss makes it particularly suitable for applications that are sensitive to reflected light, such as long-distance fiber optic communications and Wavelength Division Multiplexing (WDM) systems.
Practical application scenarios of UPC and APC optical fiber patch cords
Application of UPC optical fiber patch cord
Data Center: In the internal wiring of data centers, UPC fiber optic patch cords are often used for short-distance, high-bandwidth connection requirements, such as the connection between servers and switches. Its low insertion loss and good return loss performance are sufficient to meet the needs of most data centers.
Enterprise Local Area Network (LAN): UPC optical fiber jumpers are also widely used in optical fiber cabling of enterprise LANs to support high-speed Internet access and internal data exchange.
Test environment: Since the return loss of UPC connectors is low and reflected light does not easily affect the test results, UPC jumpers are also a common choice in fiber optic testing instruments.
Application of APC optical fiber patch cord
Telecommunications and Broadcast Communication: In telecommunications and broadcast communication systems that require long-distance signal transmission, APC fiber optic patch cords are the first choice. Its extremely low return loss can effectively reduce signal reflection in long-distance transmission and maintain signal clarity and stability.
Fibre-to-the-home (FTTH): In fiber-to-the-home (FTTH) applications, APC fiber optic patch cords ensure that home users can obtain high-quality broadband services due to their excellent return loss performance.
Wavelength division multiplexing (WDM) system: The optical fiber signal strength requirements in WDM systems are high. APC optical fiber jumpers can reduce noise caused by reflected light, thereby supporting more efficient multi-wavelength transmission.
How to choose UPC or APC fiber optic patch cord in practical applications
Select according to network requirements
Short-Distance vs. Long-Distance Transmission: For short-distance transmission, especially connections within enterprise LANs and data centers, UPC fiber optic patch cords can provide sufficient performance at a relatively low cost. For long-distance transmission, especially telecommunications networks that need to span tens of kilometers or even further, APC fiber optic patch cord performs better due to its low return loss.
Reflected light sensitivity: If the system is very sensitive to reflected light, such as a WDM system, APC fiber optic patch cord is a more suitable choice. Although UPC fiber optic patch cord has better reflection suppression, it may still not be able to completely avoid optical signal interference in such applications.
Consideration of economic costs
Cost comparison: Normally, the cost of APC fiber optic patch cord is higher than that of UPC fiber optic patch cord because its production process is more complex and requires higher technical requirements. However, for applications requiring extremely high signal integrity and stability, the additional cost of APC jumpers is worth it.
Maintenance and management
Cleaning and Maintenance: Both UPC and APC fiber optic patch cords require regular cleaning and maintenance to ensure the cleanliness of their end faces. Especially for APC jumpers, due to its beveled end face design, you need to be more careful when cleaning to avoid damaging the end face or leaving contaminants.
Conclusion
UPC and APC fiber optic patch cords each offer unique advantages and applications. UPC fiber optic patch cords are ideal for most short-distance, high-bandwidth applications due to their low insertion loss and minimal return loss. The extraordinarily low return loss of APC fiber optic patch cords makes them ideal for long-distance transmission and high-precision applications. In actual applications, the decision to use UPC or APC fiber optic patch cables should be made based on specific network needs, economic considerations, and system technical specifications. To satisfy the growing need for data transmission, fiber optic networks’ performance and reliability can be significantly improved by carefully selecting and applying fiber optic patch cables.
