1.1 The grinding angle is different.

PC indicates Physical Contact. PC is micro-spherical grinding and polishing, the ferrule surface is ground into a slight sphere, and the optical fiber core is located at the highest point of bending, which can effectively reduce the air gap between the optical fiber components, so that the two endfaces reach physical contact.

 

UPC(Ultra Physical Contact) : hyper physical endface. The UPC connector endface is not completely flat and has a slight curvature to achieve more accurate docking. UPC is based on PC more optimized endface polishing and surface finish, the endface looks more dome-shaped.

 

TheAPC (Angled Physical Contact) is called the angled physical contact, and the endface of the optical fiber is usually ground to an 8° angled surface. The 8° bevel makes the endface tighter and reflects light through its bevel Angle to the cladding rather than directly back to the light source, providing better connection performance.

 

2.2The insertion/return loss is different

Different grinding methods determine the fiber transmission quality, which is mainly reflected in return loss and insertion loss. Insertion Loss is the loss of a signal through a connector or cable. In general, the typical insertion loss of PC, UPC, and APC connectors should be less than 0.3dB. UPC/PC connectors are generally easier to achieve with low insertion losses due to smaller air gaps compared to APC connectors. Insertion losses can also be caused by dust particles between the end faces of the connector.

 

Return Loss, also known as reflection loss, is a parameter that indicates the reflection performance of a signal. It is usually represented by a negative dB value, the higher the parameter of the value, the better. The end face of the APC connector is inclined polished,therefore, the return loss of APC connectors is usually better than that of UPC connectors. Under normal circumstances, the return loss of optical fiber jumper using PC grinding is -40dB. The UPC return loss is higher than that of a PC, generally at -55dB (or even higher). The APC industry standard return loss is -65dB. When the UPC connector is used, some of the reflected light will be emitted back to the light source, while the oblique endface of the APC connector will cause some of the reflected light to reflect atan Angle to the cladding, thus reducing more reflected light back to the light source. This is the main factor that causes the difference in return loss.