An optical fiber connector terminates the end of an optical fiber, and enables quicker connection and disconnection than splicing.

There is 2 factors: 

1. The epoxy quantity not enough , when the epoxy not enough, can not fixed the fiber completely, when have any Vibration or external force, the fiber easy broken. 

2. The buffer is not inserted into the metal flange of the ferrule.  if the fiber without the protection of the buffer, easy broken in any Vibration or external force. 

3 common factors:

1.The end face of the fiber connectors, when it is durty, has scratch, the scratch , dust or oil will affect the connection of fiber, make the loss high.

2. The fiber adapter sleeve is too tight or loose , which make the connection unstable, and cause loss high.

3. The fiber adapter sleeve durty, the dust or oil make the fiber connection discontinuous. 

Fiber optic fast connector has two types:

1. Direct installing type. the structure of this type fast connector is very simple, so it is easier to make with a lower cost.It has short  points:it has strict requirements on the fiber diameter, the endface of cutting surface, the strength of holding fiber, the fiber length of  cleaving.Any of them will affect the loss of connection.Thus the return loss is bad. It requres the operater be skillful. The product structure principle is as follows:

Fiber optic fast connector direct installing type

The direct installing fast connector more used in urgent reparing of the cable connection while less used in ftth fiber connection to the home.

2. Pre- terminated  fast connector:the fiber is pte installed in the ferrule and polished.when install, the end user only need well cut  the fiber with fiber cleave and use hand to connect cable.There is matching liquid in the ferrule fange, and well polished thus have better return lods result and easy install. The product structure principle is as follows:

Fiber optic fast connector Pre-Embedded type

With a low insertion loss<0.5dB and high return loss>45dB it is more reliable and stable and widly used in fiber to the home.

There are 5 types of fiber pigtail in the fiber optic transmission system , SC/PC, FC/PC, LC/PC, E2000/APC, ST/PC. The pigtail is terminated in one side and empty in other side. The empty side will be fused to other cable count by fusion splicer. It is usually used in fiber optic terminal box to connect the cable to fiber media converter. 
The fiber pigtail has singlemode and multimode. Multimode is usually orange with wavelength 850nm  and transmision distance of 500M, mostly used in short distance interconnection. The Singlemode fiber pigtail is yellow in color with wavelengths of 1310nm and 1550nm and transmission distance above 2KM. The fiber optic fusion splicing can connect the fiber with fiber and fiber pigtail. It fuses the bare fiber and the pigtail as a whole. The pigtail has a terminated fiber connector. The fiber connector can be connected to the fiber media converter. Then the fiber and the UTP cable are conneccted. The tools used in the fiber optic fusion splicing including: fiber optic termination box, fiber optic media converter, fiber optic pigtail, fiber optic adapter, fiber optic stripper, fiber optic cleaver etc.