In the evolution of fiber optic technology, connector polishing styles play a crucial role in ensuring low reflection and stable signal transmission. Among these, the PC (Physical Contact) polish was once the industry standard but has gradually given way to UPC and APC types. This article explains why PC connectors are becoming obsolete and what technologies are taking their place.
1. What Is PC Polishing?
PC, or Physical Contact polishing, refers to a connector endface that is slightly curved to ensure two fibers make physical contact, minimizing air gaps and reflection. It was developed to improve upon the older flat-polished connectors that suffered from high return loss (around –14 dB).
With PC polishing, return loss was significantly reduced to approximately –30 dB to –40 dB, which was sufficient for early multimode and short-distance single-mode applications such as early telecom systems.
2. Why PC Polishing Is Being Replaced
(1) Limited Optical Performance
As network speeds increased, PC’s return loss level (around –30 dB) became inadequate. In modern single-mode applications, reflected light can interfere with transmitters, causing signal instability and higher bit error rates.
By contrast, UPC (Ultra Physical Contact) offers around –50 dB, while APC (Angled Physical Contact) achieves –60 dB or better. This performance gap makes PC polishing unsuitable for today’s high-precision optical networks.
(2) Incompatibility with Modern Equipment
Most optical devices today—such as OLTs, ONUs, transceivers, and DWDM modules—are designed for UPC or APC connectors. Mixing PC connectors with newer ports can cause mismatched contact surfaces, resulting in poor alignment and higher insertion loss.
As a result, the PC interface is rarely found on new optical equipment, reducing its relevance in modern systems.
(3) Diminished Cost Advantage
Historically, PC connectors were cheaper to produce due to simpler polishing. However, with automated polishing and tighter production tolerances, the cost difference between PC and UPC/APC has become minimal. Manufacturers now prefer to standardize on UPC and APC lines to meet modern performance requirements.
(4) Industry Shift Toward Low Reflection Standards
Today’s fiber networks—from FTTH and FTTA to data centers and CATV systems—require extremely low reflectance to maintain high bandwidth and signal integrity. UPC and APC connectors, especially APC with its 8° angled endface, meet these demands by redirecting reflected light into the cladding instead of back into the core.
This trend toward high-performance, low-reflection design makes PC polishing less competitive.
3. Comparison of PC, UPC, and APC Connectors
| Type | Endface Geometry | Typical Return Loss | Main Applications |
|---|---|---|---|
| PC | Slightly curved (no angle) | ≈ –30 to –40 dB | Legacy multimode, basic telecom |
| UPC | Highly polished curved surface | ≈ –50 dB | FTTH, data, telecom networks |
| APC | 8° angled surface | ≈ –60 dB or higher | FTTx, CATV, WDM, 5G systems |
While PC still exists in older systems, it is now regarded as an outdated standard gradually phased out by UPC and APC due to superior reflection control and compatibility.
4. Where PC Is Still Used
PC connectors can still be found in:
Legacy multimode networks (OM1/OM2)
Low-cost, short-range links where reflection is less critical
Certain older telecom or industrial installations
However, as networks upgrade to higher data rates and lower tolerances, these applications continue to shrink.
Conclusion
It’s clear that PC polishing has reached the end of its lifecycle in mainstream fiber optic systems. With the rise of high-speed, low-reflection requirements, UPC and APC connectors have become the new global standards.
For modern installations, APC is preferred for precision systems like FTTx and CATV, while UPC remains the go-to for general data and telecom use. PC connectors now represent an important historical step in fiber development—but one that’s quickly being replaced by more advanced technologies.
