Compatibility between SFP optical module and PC/APC/UPC fiber patch cord


Optical fiber jumper is an indispensable connecting line in fiber optic wiring. When purchasing optical fiber jumper, we always see the words PC/APC/UPC, such as LC/APC fiber jumper, FC/APC fiber jumper, SC/PC fiber patch cords, ST/UPC fiber patch cords, etc., do you know what PC/APC/UPC stands for? Are SFP optical modules compatible with PC/APC/UPC fiber patch cords? Through the detailed introduction of this article, I believe you will find the answer.


1. What is PC/APC/UPC?

PC/APC/UPC refers to different grinding methods of optical fiber connectors on optical fiber jumpers, and different grinding methods determine the optical fiber transmission quality, mainly reflected in return loss and insertion loss. So what's the difference between these three grinding methods?


Fiber Jumper

1. What is a PC?

PC (Physical Contact, and physical contact) is the most common grinding method for optical fiber connectors on optical fiber jumpers, and is widely used in telecom operator equipment. Although the end face of the optical fiber connector looks flat, in fact, the end face is slightly bent and polished, and the highest point of bending is the center of the fiber core, which can effectively reduce the air gap between the optical fiber components. The return loss of the jumper is -40dB.


2. What is UPC?

UPC (Ultra Physical Contact) is an evolution of PC, which optimizes the end face polishing for better surface finish. Like PC, UPC has the highest bending point in the center of the fiber core, but the return loss of UPC is higher than that of PC, generally -50dB (or even higher). It is usually used in Ethernet network equipment (such as ODF fiber optic patch panels, media converters and fiber optic switches, etc.), and is also used in telephone systems.

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3. What is APC?

APC (Angled Physical Contact) is the latest technology for optical fiber end face grinding. The end face adopts an 8-degree angle grinding method, which makes the end face grinding more accurate, which can effectively reduce reflection and return loss of about -60dB. APCs are typically used in high wavelength range optical RF applications such as CATV.


Note: Return loss (ie, reflection loss) refers to the reflection caused by the impedance mismatch in the optical fiber link, which is the reflection of a pair of lines themselves. This percentage of reflected light is usually expressed in -dB, the higher the better.


2. What is the difference between PC/APC/UPC?

After the above detailed introduction to PC/APC/UPC, you will find that PC/APC/UPC has differences in end face, return loss, application and so on.


Both PC and UPC are flat interface types. PC is the earliest grinding method with poor return loss; UPC is evolved based on PC structure, and its return loss is better than PC; while APC is an end-face belt There is an 8-degree grinding method, which can effectively reduce reflection. Compared with PC and UPC, the return loss is better, and it is more suitable for high-bandwidth and long-distance links.


3. How to correctly select PC/APC/UPC fiber jumpers for SFP optical modules?

As we all know, the SFP optical module has two transmission channel ports, one of which is used to send signals, and the other port is used to receive signals. Usually, the transmission of signals needs to be realized through optical fiber jumpers. The above mentioned three different grinding types of fiber jumpers for PC/APC/UPC. Can these three fiber jumpers be used with SFP optical modules? In fact, because the connection ports of SFP optical modules are flat, so It can only be connected with the optical fiber jumper of PC and UPC. If it is connected with the optical fiber jumper of APC, it will cause invalid connection or network failure.


In principle, optical fiber connectors with three different grinding methods of PC/APC/UPC cannot be interconnected, but since the optical fiber end face structures of PC and UPC are both flat (with slight bending) structures, the two can be Compatible and interchangeable, but there will be polishing quality issues, but will not cause any damage to the connector. Although SFP optical modules can be connected with PC and UPC optical fiber patch cords, in order to ensure the goodness of optical fiber links, it is recommended that you use SFP optical modules with UPC optical fiber patch cords.


The fiber end face structure of APC is completely different from that of PC and UPC, so APC cannot be interconnected and compatible with them. If it is forcibly connected, it will cause damage to the connector; if you want to connect APC and UPC/PC, you must connect the two through APC-UPC/APC-PC conversion fiber jumpers, but considering the waste of resources and wiring difficulties For other reasons, FS does not recommend you to do this, so it is best not to use APC optical fiber jumpers on SFP optical modules. Unless the manual of the SFP optical module says that APC optical fiber jumpers are allowed, it is recommended that you use UPC optical fiber jumpers.


All in all, PC and UPC fiber jumpers can be used on Ethernet equipment such as fiber switches, and used in conjunction with SFP optical modules; APC fiber jumpers are mainly used in FTTx, passive optical network (PON) and wavelength division multiplexing (WDM) , it is best not to use with SFP optical modules. The specific choice depends on your network needs.


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