Many theoretical and experimental investigations have reported that G.654.E fiber with ultra-low-loss and large-effective-area features can significantly enhance the long-haul transmission performance of 100G, 200G, 400G and higher speed networks compared with the conventional G.652 fiber. Therefore G.654.E fiber is deemed as a promising candidate to optimize the transmission performance for next-generation ultra high-speed long-haul optical networks.
G.654.E fiber is a new kind of cut-off wavelength shift single-mode optical fiber. It is compiled with the G.654.E standard issued by ITU-T in November 2016, which is the latest revision of "ITU-T Recommendation G.654 - Characteristic of a Cut-Off Shifted Single-mode Optical Fiber and Cable". The former revisions of ITU-T G.654 standard include G.654.A, G.654.B, G.654.C and G.654.D which describe fibers typically used in submarine applications.
Like G.654.A, G.654.B, G.654.C and G.654.D single-mode fibers, G.654.E fiber also features ultra-low-loss and large-effective-area. However, it has great advantages in operating temperature, macro bending loss, etc. To be specific, G.654.A, G.654.B, G.654.C and G.654.D fiber cables are mainly applied in marine environments where the temperature is constant about -1℃ to 2℃. While G.654.E fiber is designed to be used on land where temperature changes are larger from -65℃ to 85℃. Besides, G.654.E fiber can also resist all kinds of stress and have a great anti-bending performance to meet environment pressure, bending stress, mechanical impact in the complex terrestrial environment. All these features enable G.654.E fiber to be suitable for high speed long-haul terrestrial optical networks rather than trans-oceanic applications. The following table shows the fiber attribute and cable attribute differences of G.654.A, G.654.B, G.654.C, G.654.D and G.654.E single-mode fibers:
|G.654 A||G.654 B||G.654 C||G.654 D||G.654.E|
|Mode Field Diameter||Wavelengths||1550nm||1550nm||1550nm||1550nm||1550nm|
|Core diameter||9.5 ~ 10.5um||9.5 ~ 13.0um||9.5 ~ 10.5um||11.5 ~ 15.0um||11.5 ~ 12.5um|
|Tolerance||± 0.7um||± 0.7um||± 0.7um||± 0.7um||± 0.7um|
|Cladding Diameter||Clad Diameter||125um||125um||125um||125um||125um|
|Tolerance||± 0.7um||± 1um||± 0.7um||± 0.7um||± 1um|
|Clad Non-Circularity||Max.||≤2.0 %||≤2.0 %||≤2.0 %||≤2.0 %||≤2.0 %|
|Clad Concentricity Error||Max.||≤ 0.8um||≤ 0.8um||≤ 0.8um||≤ 0.8um||≤ 0.8um|
|Cable Cutoff Wavelength||Max.||≤ 1530 nm||≤ 1530 nm||≤ 1530 nm||≤ 1530 nm||≤ 1530 nm|
|number of turns||100 turns||100 turns||100 turns||100 turns||100 turns|
|Max. at 1652nm||0.5dB||0.5dB||0.5dB||0.5dB||0.1dB|
|Chromatic Dispersion Coefficient||D1550max||20ps/(nm · km)||20ps/(nm · km)||20ps/(nm · km)||23ps/(nm · km)||23ps/(nm · km)|
|S1550max||0.070ps/nm2 · km||0.070ps/nm2 · km||0.070ps/nm2 · km||0.070ps/nm2 · km||0.070ps/nm2 · km|
|Attenuation coefficient||Max. at 1550 nm||0.22dB/km||0.22dB/km||0.22dB/km||0.22dB/km||0.23dB/km|
|PMD coefficient||M||20 cables||20 cables||20 cables||20 cables||20 cables|
OSNR（Optical Signal to Noise Ratio) is one of the key parameters which has a great impact on optical network transmission performance. G.654.E fiber has a very small macro bend attenuation and a large effective area, which helps improve the OSNR value by reducing transmission loss and delivering higher launch power. Here uses the Figure of Merit (FOM) methodology to compare the transmission performance of G.654.E and other terrestrial long-haul optical fibers. FOM on the y-axis corresponds to an increase in Q-factor (a concise performance metric for fast characterization of optical digital transmission systems) relative to standard G.652 fiber which can be translated into reach improvement. 1 dB advantage represents 25% reach increase, 2 dB advantage represents 60% reach increase, and 3 dB advantage represents 100% reach increase. As we can see from the following picture, G.654.E fiber provides the best transmission performance.
The high speed long-haul optical transport network faces enormous challenges in improving unrepeatered transmission distance. According to the results of abundant experiments and practical researches, the large-effective-area design of G.654.E optical fiber increases the size of the fiber core region, which enables higher power of optical signal to be propagated. Therefore this kind of fiber can extend optical transmission distance by 70% - 100% compared to the G.652 optical fiber. It is proven that G.654.E fiber can extend the transmission distance of relay nodes up to 900 km or more. And a field experiment demonstrates that G.654.E single-mode fiber can achieve 2000km WDM transmission distance of 400 Gbps combined with erbium-doped fiber amplifier (EDFA) and backward distributed Raman amplifier (DRA).
Compared to G.652 fiber, the use of G.654.E fiber will increase the cost of fiber optic cable as it is more expensive. However, this cost is slight compared to deploying G.652 fiber for high rate optical network systems. This is because the use of G.652 fiber cables will incur much more quantities and cost on optical relay nodes as G.652 fiber has much shorter unrepeatered transmission distance. While G.654.E fiber with longer transmission distance can reduce the total number and cost of optical relay nodes and systems in the high speed long-haul networks.
Ultra-low-loss and large-effective-area G.654.E fiber can significantly improve the transmission performances of 100 Gbit/s, 200g Gbit/s, 400 Gbit/s and beyond 400 Gbit/s coherent optical systems instead of the standard single-mode fiber. It is expected to gain strong market adoption as high speed 100G, 200G, 400G networks are deployed on a large scale for data center interconnect (DCI), metro and other long-haul optical networks in the coming years.