What is G.654E Fiber?

The development of communication technology is changing by the day, and the single-core capacity in optical fiber communication is doubling every 3 to 5 years, but the main types of communication optical fibers, and the main optical fiber transmission indicators have not changed significantly for many years. The G.652D optical fiber, which is currently in widespread usage, has a nearly 20-year history.

A new variety of G.654E  optical fiber has been employed in various long-distance trunk lines in recent years, with good results. What exactly is G.654E  fiber? Will G.654E  fiber eventually replace G.652D?

Ⅰ.  History of G.654 Optical Fiber

A pure silica core single-mode fiber for 1550nm wavelength was developed in the mid-1980s to satisfy the needs of long-distance communication of underwater optical cables, and its attenuation around this wavelength was 10% lower than that of G.652  fiber.

G.654 fiber was the name given to it at the time, and it stood for "minimum attenuation single-mode fiber at 1550 nm wavelength."

WDM technology was first employed in submarine optical communication networks in the 1990s. When dozens or even hundreds of optical channels are simultaneously transmitted in an optical fiber using  WDM  technology, and high-power multi-wavelength optical signals are coupled into an optical fiber and gathered on a small interface using fiber amplifiers, the optical fiber begins to exhibit nonlinear characteristics.

The transmission performance of the system will gradually deteriorate when the input optical power exceeds a specific value due to the nonlinear effect of the fiber when the input optical power exceeds a certain value.

Figure. 1

The optical power density of the fiber core affects the nonlinear impact of the fiber. When the optical power of the fiber is constant, the nonlinear impact can be decreased by increasing the effective area of the fiber and lowering the optical power density of the fiber core. As a result, G.654  fiber started working on a paper about improving the effective area.

The increase in the effective area of the fiber will result in an increase in the cut-off wavelength, but this must be managed so that the fiber's use in the C-band (1530nm 1565nm) is not harmed; thus, the cut-off wavelength of the G.654  fiber is set at 1530nm.

The nomenclature was modified to "Cut-off wavelength shifted single-mode fiber" when the  ITU  amended the G.654  fiber standard in 2000.

Low attenuation and a broad effective area are two properties of G.654  fiber thus far. Following that, the G.654  optical fiber used for submarine cable connection was primarily tuned for attenuation and effective area, eventually dividing into four subclasses: A/B/C/D.

Ⅱ.  Characteristics of G.654E  Fiber

Inland trunk transmission lines, G.652  D is the most common optical fiber. The nonlinear effect of optical fiber has a growing impact on transmission performance when the single carrier rate of  WDM systems approaches 100G. G.654  optical fiber is inherently appealing to researchers. Long-distance trunk transmission system to be landed.

The macro bending loss criteria of terrestrial G.654   optical fibers are substantially stricter than those for subsea use (the macrobending loss is consistent with G.652D), and the effective area and attenuation indicators are wider than those for subsea usage. G.654E  fiber became the industry standard. The main transmission index differences of each  G.654  fiber subclass are indicated in the table below.

Figure. 2

Ⅲ.  Advantages and disadvantages of G.654E  compared to G.652D 

(1) Advantages of G.654E fiber

The OSNR  tolerance requirement of a WDM system with a single carrier rate exceeding 100G increases as the single carrier rate increases. The optical power of the incoming fiber and the attenuation of the optical amplifier section are both elements that affect OSNR. G.654E  fiber's high effective area and low attenuation properties can significantly increase OSNR, 

Figure. 3

G.654E optical fibers have two different effective areas: 110 um2 (A110) and 130 um2 (A130) (A130). A110 and A130 fibers were used in China's trunk lines from 2015 to 2018. After 2018, only A130 fiber was used to construct trunk lines.  G.654E  (A130) fiber has a 47 percent greater effective area than G.652D  fiber (A80) fiber. Under the condition that the nonlinear effect remains unchanged, the optimal input optical power can be increased by about 1.7dB.

G.654E fiber has a typical attenuation of roughly 0.02dB/km less than G.652D  fiber. The attenuation of  G.654E fiber is around 1.6dB lower than that of G.652D  fiber over an 80km optical amplifier section.

Because the location of the optical amplifier station in the land trunk transmission system is frequently defined, increasing optical power entering the fiber and lowering optical fiber attenuation cannot greatly reduce the number of optical amplifier stations. The OSNR  of G.654E fiber can be enhanced by around 3dB when compared to G.652  fiber assuming the optical amplifier station settings are essentially unchanged.

(2) Disadvantages of G.654E fiber

G.654E fiber has a cutoff wavelength of 1530nm, which limits its use at wavelengths below 1530nm. At the moment, transmission systems in the metropolitan area network with a single optical module surpassing 100G, such as the core layer and aggregation layer systems of 5G backhaul, usually work around the 1310nm wavelength (O-band). As a result, G.654E fiber is not suited for use in a metropolitan area network.

Figure. 4

The market size of G.654E optical fiber is significantly smaller than that of G.652D  optical fiber, which contributes to its high pricing. G.654E bare fiber currently costs nearly ten times as much as G.552D fiber.

Ⅳ.  Application scenarios of G.654E fiber

The optical cable skins employing G.654E optical fibers are approximately 15,000 kilometers long among the optical cables created by various operators in the inter-provincial and intra-provincial trunk lines, and the use effect is essentially compatible with the above analysis. This is sufficient to justify the use of G.654E optical fiber in interprovincial trunk lines.

Intra-provincial trunk lines often have a lower single-carrier rate, a smaller number of optical amplifier sections in the multiplex portion, and lower OSNR  tolerance requirements than inter-provincial trunk lines. As a result, the use of G The demand for.654E fiber isn't high. It is suggested that G.652D  low-loss fiber (the unit price of bare fiber is about 1.5 to 2.0 times that of ordinary G.652D) be used.

Because the wavelengths used by various optical transmission systems in the metropolitan area network are inside the cutoff wavelength range of the G.654E optical fiber, it is not appropriate for use in metropolitan area transmission.