1 Introduction
G. 657 optical fiber is also called bending loss-insensitive optical fiber. The fiber optic cable that is thinner than ordinary telephone line used for FTTH entry is G. 657 fiber. Without G. With 657 fiber, there is no large-scale application of FTTH. G. 657 optical fiber is divided into multiple sub-categories, currently commonly used is G. 657A2.
G. 652 optical fiber is the most widely used optical fiber in the metropolitan area network. In addition to the FTTH home fiber optic cable, all other communication optical fiber cables in the metropolitan area are basically G. 652 fiber. G. 652 optical fiber is divided into 4 sub-categories, and the current one that is generally used is G. 652D.
With G. Compared with 652D fiber, G. How good is the bending resistance of 657A2 fiber?
2 G in the standard. 657 and G. Minimum bending radius of 652 fiber
In the relevant standards, G. The minimum bending radius of 657A2 fiber is recommended to be 7.5mm, while G. The minimum bending radius of 652 fiber is required to be no less than 30mm, but the meaning of the minimum bending radius of the two here is completely different.
G. The minimum bend radius of the 657A2 fiber refers to: the fiber is loosely wound with a radius of 7.5mm, and the additional attenuation measured at 1550nm/1625nm does not exceed 0.5dB/1.0dB, respectively.
G. The minimum bend radius of 652D fiber refers to: the fiber is loosely wound with a radius of 30mm for 100 turns, and the additional attenuation measured at 1625nm does not exceed 0.1dB.
The additional loss caused by the bend of the optical fiber with a bend radius much larger than its diameter is called macrobending loss. Obviously, G． 657A2 fiber and G. The minimum bending radius of 652D fiber is not comparable.
3 G. 657 and G. 652 fiber bending resistance measured
When installing the FTTH home fiber optic cable, in order to facilitate the termination of the home fiber optic cable, the installation personnel often weld the FTTH home fiber optic cable to a small section of pigtails at the fiber splitting box and the ONT (commonly known as “optical cat”). The fiber type inside is G. 652D, the fiber optic cable type in the FTTH home fiber optic cable is G. 657A2.
Because the laying environment of the pigtail and the home optical cable are the same, the size is equivalent (the diameter of the pigtail is 2.0mm, and the short axis/long axis diameter of the home optical cable is 2.0mm/3.0mm). Therefore, compare the pigtail and The anti-bending performance of the home optical cable is more realistic and can basically reflect the G． 652D and G. The difference in bending resistance of 657A2 fiber.
Since the macrobending loss of the optical fiber in the ODN is mainly affected by the downstream wavelength, only the additional loss of the pigtail and the home fiber optic cable with different radii at 1490nm wavelength is tested. Flick the pigtail (G. 652D) a few streets, especially under the small bending radius, the bending resistance of the home optical cable is even better.
4 Conclusions and recommendations
Because G. 657 and G. There is a huge difference in the bending resistance of 652 fiber, and the pigtail itself is relatively soft, and it is very prone to bend with a small radius. The fault ratio is as high as 50%. Therefore, it is not advisable to use pigtails to terminate the home optical cable during FTTH installation. A pre-terminated butterfly optical cable (as shown in the figure below) should be used for installation and termination.
A pre-terminated butterfly optical cable
