G.657 optical fiber is also known as bending loss insensitive optical fiber. G.657 optical fiber is used in the optical fiber cable that is thinner than ordinary telephone lines for FTTH households. Without G.657 fiber, there is no large-scale application of FTTH. G.657 fiber is divided into several sub-categories, and G.657A2 is currently commonly used.
G.652 optical fiber is the most widely used optical fiber in the metropolitan area network. Except for the FTTH home optical cable, G.652 optical fiber is basically used in other communication optical cables in the metropolitan area. G.652 optical fiber is divided into 4 sub-categories, currently G.652D is generally used.
Compared with G.652D fiber, how strong is the bending resistance of G.657A2 fiber.
Minimum bend radius requirements for G.657 and G.652 fibers in the standard
In the relevant standards, the minimum bending radius of G.657A2 fiber is recommended to be 7.5mm, while the minimum bending radius of G.652 fiber is required to be no less than 30mm, but the meaning of the minimum bending radius of the two is completely different.
g. The minimum bending radius of 657A2 fiber refers to: the fiber is loosely wound for 1 turn with a radius of 7.5mm, and the additional attenuation measured at 1550nm/1625nm does not exceed 0.5dB/1.0dB, respectively.
The minimum bending radius of G.652D fiber refers to: the fiber is loosely wound for 100 turns with a radius of 30mm, and the additional attenuation measured at 1625nm does not exceed 0.1dB.
The additional loss caused by the bending of the fiber when the bending radius is much larger than its diameter is called the macrobending loss. The macrobending characteristics of G.657A2 fiber and G.652D fiber are shown in the following table.
Obviously, the minimum bending radius of G.657A2 fiber and G.652D fiber is not comparable here.
Measurement of bending resistance of G.657 and G.652 optical fibers
When installing the FTTH home optical cable, in order to facilitate the end of the home fiber optic cable, the installers often splicing a small section of pigtail at the fiber optic cable distribution box and the ONT (commonly known as "optical cat").
The optical fiber type in the pigtail is G.652D, and the optical cable type in the FTTH home optical cable is G.657A2.
Because the laying environment of the pigtail fiber and the home optical cable is the same, the size is the same (the diameter of the pigtail fiber is 2.0mm, and the diameter of the short axis/long axis of the home fiber optic cable is 2.0mm/3.0mm). Therefore, comparing the pigtail fiber and the home fiber optic cable The bending resistance of the optical cable is more practical, and it can basically reflect the difference between the bending resistance of G.652D and G.657A2 optical fibers.
Since the macrobending loss of the optical fiber in ODN is mainly affected by the downlink wavelength (see the article "Influence of Insufficient Optical Fiber Bending Radius on ODN Link Loss"), only pigtails and home optical cables are tested at 1490nm wavelength with different radii around 1 Additional loss of laps, part of the die tested
It can be seen from the test results that the bending resistance of the home optical cable (G.657A2) is a few blocks away from the tail fiber (G.652D). Especially under the small bending radius, the bending resistance of the home optical cable is better.
conclusion and suggestion
Since 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 easy to bend with a small radius
According to the statistics of installation failures in a metropolitan area network, installation failures caused by insufficient bending radius of pigtails account for as high as 50%. Therefore, it is not advisable to use pigtails to end the home optical cable when FTTH is installed. , The prefabricated butterfly cable should be used for placement and termination.
