What is G.657 Fiber Optic? G.657 Fiber vs G.652 Fiber, What is the Difference?

What is G.657 fiber? G.657 fiber is a bend-attenuation-insensitive single-mode optical fiber cable for access networks. Its standard was released by the International Telecommunication Union ITU-T in November 2006. It is a new type of optical fiber developed on the basis of G.652 fiber to achieve the goal of fiber to the home (FTTH). G.657 optical fiber is divided into two categories, A and B, according to whether it is compatible with G.652 optical fiber. Among them, category A is more common.

What is G.657.A1 fiber?

G.657.A1 fiber is a specification designed for special cabling environments. Its core features include

Bending radius advantage and superior mechanical properties. G.657.A1 optical fiber has a smaller bending radius, making it suitable for cabling environments that require high bending. Such as FTTH (fiber to the home) applications in homes and businesses. G.657.A1 fiber excels in mechanical properties. It is more suitable for scenarios that require frequent connections and bending. This fiber can adapt to turns and bends more flexibly to ensure that signal quality is not affected.

What is G.657.A2 fiber?

G.657.A2 is a specification further developed on the basis of G.657.A1. Its main features include

Smaller bending radius and optimized mechanical properties. Compared with G.657.A1, G.657.A2 has a smaller bending radius. It is more suitable for scenarios with limited space and more demanding bending requirements. G.657.A2 fiber is further optimized in mechanical properties to provide better connection and bending performance. G.657.A2 optical fiber is commonly used in fiber access networks. Especially when it is necessary to introduce fiber into the interior of a building. Its smaller bending radius makes it easier to lay the cable in a limited space.

What is G.652 fiber?

G652 fiber is the most widely used fiber in metropolitan area networks. In addition to FTTH fiber cables, all other communication cables used in metropolitan areas are basically G652 fibers. G652 fiber is divided into 4 subcategories, and the most commonly used one is G.652.D fiber.

G.657 Fiber Optic vs G.652 Fiber Optic, What is the difference?

Minimum bending radius requirements. This is one of the most significant differences between them. In relevant standards, the minimum bending radius of 7.5 mm G.657.A2 fiber is recommended. The minimum bending radius of G.652 optical fiber is required to be no less than 30 mm. But their minimum bending radii have completely different meanings. The minimum bending radius of G.657.A2 fiber refers to: The fiber is loosely wound and the radius is 7.5 mm. The additional attenuation measured at 1550nm/1625nm does not exceed 0.5dB/1.0dBG. The minimum bending radius of G652D fiber refers to: The fiber is loosely wound around a 100 circle with a radius of 30 mm. The additional attenuation measured at 1625nm does not exceed 0.1dB.

The additional loss caused by bending an optical fiber with a bend radius much larger than its diameter is called macrobend loss.

G.657 and G.652 Fiber Bending Resistance Measurement Performance

When installing FTTH optical cable, in order to facilitate the termination of the optical cable. Installers often solder FTTH fiber optic cable to a small piece of pigtail fiber at the fiber optic breakout box and ONT (commonly known as the “optical modem”).

Since the laying environment of optical fiber pigtails and indoor optical cables are the same, the dimensions are the same. The fiber pigtail diameter is 2.0 mm, and the short axis/long axis diameter of the indoor optical cable is 2.0 mm/3.0 mm. Therefore, it is more realistic to compare the bending performance of fiber optic pigtails and indoor fiber optic cables. It can basically reflect the difference in bending resistance between G.652.D and G. 657.A2 fiber.

Since the macro-bending loss of optical fibers in ODN is mainly affected by the downstream wavelength, only the additional losses of optical fiber pigtails and indoor optical cables wound with different radii at the 1490nm wavelength were tested. A portion of the mold tested is shown below.

Bending Radius(mm)	Additional Loss
	Optic Fiber Pigtail(G.652D)	Indoor Fiber Optic Cable
10.0	0.18	0.02
7.5	1.60	0.06
5.0	8.13	0.37
3.8	15.61	0.65
2.5	–	1.71
1.5	–	6.68