What is G.654 Cut-off Shifted Single-Mode Optical Fiber?

ITU-T has classified the single-mode fibers into 6 categories or groups as below;

1. ITU-T G.652 (from A to D, Dispersion un-shifted Single -Mode Fiber)
2. ITU-T G.653 (Dispersion Shifted Single-Mode Fiber
3. ITU-T G.654 (Cut-off Shifted Single Mode Fiber)
4. ITU-T G.655 (Non-Zero Dispersion Shifted Single-Mode Fiber
5. ITU-T G.656 (Wide Band Non-Zero Dispersion Shifted Single-Mode Fiber)
6. ITU-T G.657 (Bend-Insensitive Single-Mode Fiber)

As we can see, ITU-T G.654 fiber is in the 3rd row and is described as Cut-off Shifted Single-Mode Fiber. ITU-T Recommendation G.654 details the geographical, mechanical and transmission characteristics of Cut-off Shifted Single-Mode Optical Fiber and Cable.

ITU-T G.654 fiber has a zero dispersion at about 1300 nm but has lower attenuation at 1550nm. Most importantly, the cut-off is shifted at around 1550nm wavelength region.

ITU-T has created the specifications for Cut-off Shifted Single Mode Fiber and Cable in 1988. Since then, the recommendation has gone through 9 revisions and the 10th revision was published on 13 November 2016.

What is the wavelength range of Cut-off Shifted Single-Mode Fiber?
Cut-off Shifted Single Mode Fiber is optimized for use in the wavelength range of 1530nm to 1625nm.

What are the Applications of Cut-off Shifted Single Mode Fiber and Cable?
Cut-off Shifted Fiber, shortly known as CSF is mainly used for long-distance digital transmission applications. Therefore, CSF cables can be found in long-haul terrestrial telecommunication systems and Submarine cable systems.

How Many Types of Cut-off Shifted Single-Mode Fibers are there?
There are five categories of Cut-off shifted single-mode fibers. They are G.654A, G.654B, G.654C, G.654D, and G.654E

What is the Mode Field Diameter value of G.654 Cut-off Shifted Single-Mode Fiber?
For G.654A Category, the range of nominal values for Mode Field Diameter (MFD) of Cut-off Shifted Single Mode fiber is 9.5m to 10.5m measured at 1550nm wavelength. Tolerance could be 0.7m.

For the G.654B Category, the range of nominal values for Mode Field Diameter (MFD) of Cut-off Shifted Single Mode fiber is 9.5m to 13m measured at 1550nm wavelength. Tolerance could be 0.7m.

For the G.654C Category, the range of nominal values for Mode Field Diameter (MFD) of Cut-off Shifted Single Mode fiber is 9.5um to 10.5um measured at 1550nm wavelength. Tolerance could be 0.7um.

For the G.654D Category, the range of nominal values for Mode Field Diameter (MFD) of Cut-off Shifted Single Mode fiber is 11.5um to 15um measured at 1550nm wavelength. Tolerance could be 0.7um.

For the G.654E Category, the range of nominal values for Mode Field Diameter (MFD) of Cut-off Shifted Single Mode fiber is 11.5um to 12.5um measured at 1550nm wavelength. Tolerance could be 0.7um.

What is the Attenuation at 1550nm for the Cut-off Shifted Single-Mode Fibers?

G.654A: 0.22 dB/km
G.654B: 0.22 dB/km
G.654C: 0.22 dB/km
G.654D: 0.20 dB/km
G.654E: 0.23 dB/km

What is the Chromatic Dispersion at 1550nm for the Cut-off Shifted Single-Mode Fiber?

G.654A: 20 ps/nm.km
G.654B: 22 ps/nm.km
G.654C: 20 ps/nm.km
G.654D: 23 ps/nm.km
G.654E: 23 ps/nm.km.
There is a minimum Chromatic Dispersion requirement for the E category, which is 17 ps/nm.km

What is the PMDQ requirement for the Cut-off Shifted Single-Mode Fiber?

PMD Link Design Value or PMDQ requirement:
G.654A: 0.5 ps/√km
G.654B: 0.2 ps/√km
G.654C: 0.2 ps/√km
G.654D: 0.2 ps/√km
G.654E: 0.2 ps/√km

What is the Chromatic Dispersion Slope Requirement for Cut-off Shifted Single-Mode Fiber?

The slope of chromatic dispersion at 1550nm specified for G.654 fibers are as below;
G.654A: 0.070 ps/ nm2. km
G.654B: 0.070 ps/ nm2. km
G.654C: 0.070 ps/ nm2. km
G.654D: 0.070 ps/ nm2. km
G.654E: 0.070 ps/nm2. Km.
There is a minimum value for Chromatic Dispersion slope specified for the E category, which is 0.050 ps/ nm2.km

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Author: Fiber

Chief Editor of Fiber Optic Mania Magazine

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