Compatibility between SFP optical modules and fiber optic jumpers

Optical fiber jumper is an indispensable connecting line in optical fiber wiring. When purchasing optical fiber jumper, we will always see the words PC/APC/UPC, such as LC/APC optical fiber jumper, FC/APC optical fiber jumper, SC/PC fiber jumper, ST/UPC fiber jumper, 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 refer to different grinding methods of optical fiber connectors on optical fiber jumpers, and different grinding methods determine the quality of optical fiber transmission, mainly reflected in return loss and insertion loss. So what is the difference between these three grinding methods?

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, it is actually slightly bent and polished, and the highest point of the bend 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 evolved from PC, which optimizes the end face polishing to obtain a better surface finish. Like PC, UPC has the highest bending point at the center of the fiber core, but the return loss of UPC is higher than that of PC, generally at -50dB (or even higher). It is usually used on Ethernet network equipment (such as ODF optical fiber distribution frame, media converter and optical fiber switch, etc.), and is also used in telephone system.

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 precise and can effectively reduce reflection. The return loss is 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 impedance mismatch in the 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 have differences in end face, return loss, application, etc.

Both PC and UPC are planar interface types. PC is the earliest grinding method with poor return loss; UPC is evolved based on the PC structure, and its return loss is better than PC; There is an 8-degree grinding method, which can effectively reduce reflection, and the return loss is better than that of PC and UPC, and 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 port 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 PC/APC/UPC three types of optical fiber jumpers with different grinding types. Can these three kinds of optical fiber jumpers be used with SFP optical modules? Actually not, because the connection port of SFP optical module is flat, so It can only be connected with the fiber jumper of PC and UPC, if it is connected with the fiber jumper of APC, it will cause invalid connection or network failure.

In principle, PC/APC/UPC optical fiber connectors with three different grinding methods cannot be interconnected, but since the optical fiber end faces of PC and UPC are flat (with a slight bend) structure, the two can be Compatible and interchangeable, but there will be a problem with the quality of the finish, but it will not cause any damage to the connector. Although SFP optical modules can be connected with PC and UPC optical fiber jumpers, in order to ensure the goodness of optical fiber links, it is recommended that you use SFP optical modules with UPC optical fiber jumpers.

The fiber end-face structure of APC and PC and UPC is completely different, so APC cannot be interconnected and compatible with them. If it is forced to connect, 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 jumper, but considering the waste of resources and the difficulty of wiring For other reasons, it is not recommended that you do this, so it is best not to use APC fiber jumpers on the SFP optical module, unless the SFP optical module manual says that APC fiber jumpers are allowed, otherwise it is recommended that you use UPC fiber jumpers.

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