G652 and G655 Single mode Fiber Optics guide - Differences?

Are you turning to single-mode cables to speed your connection or your infrastructure?

As we know, multimode fiber is usually divided into OM1, OM2, OM3, and OM4. But, did you know that Single mode fibers have a classification too? And each one has a particular characteristic.

There are two primary sources of the specification of single-mode optical fiber. One is the ITU-T G.65x series, and the other is IEC 60793-2-50.

In this case, we are going to stablish the differences between G652 and G655 that belong to the ITU-T G.65x series. There are 19 different single-mode optical fiber specifications defined by the ITU-T.

Each has its exclusive specification, which reflects the evolution of transmission system technology from the earliest installation of single-mode optical fiber to nowadays.



  • 652: known as Standard single mode fiber. Its zero dispersion point is in 1300nm and it’s divided into G65 2A, B, C, D.

It is the most commonly deployed single-mode fiber. A and B have a water peak. C and D eliminate the water peak for full spectrum operation.

The G.652.A and G.652.B fibers are designed to have a zero-dispersion wavelength near 1310 nm, therefore they are optimized for operation in the 1310nm band.

The more recent variants, G.652.C and G.652.D, feature a reduced water peak that allows them to be used in the wavelength region between 1310 nm and 1550 nm supporting Coarse Wavelength Division Multiplexed (CWDM) transmission.

  • G655: also called Non zero dispersion-shifted fiber. Contains 655 A, B, C. The main characteristic is that the dispersion of 1550nm is close to zero, but not zero. It is an improved dispersion-shifted fiber to suppress four-wave mixing.

 It has a small, controlled amount of chromatic dispersion in the C-band (1530-1560 nm), where amplifiers work best, and has a larger core area than G.652 fiber.


Differences g652 and g655
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There are other types of cables in the G.65x series. Here is a little review of each one of them:

  • G653 (dispersion-shifted fiber – DSF): Compared with G.652, it has a reduced core size, which is optimized for long-haul single-mode transmission systems using erbium-doped fiber amplifiers (EDFA) and the wavelength of zero chromatic dispersion is shifted up to 1550 nm.


  • G654 (Ultra low loss optical fiber): mainly used fortransoceanic optical cable. The common core is pure SiO2, while the ordinary ones need to be doped with germanium. The loss near 1550nm is minimum, only 0.185dB/km, the dispersion is relatively large, about 17~20 ps/ (nm·km), But the dispersion is zero in the 1300nm wavelength region.

Its large core size is made from pure silica to achieve the same long-haul performance with low attenuation in the 1550nm band. These G.654 specifications entitled “Characteristics of a cut-off shifted single-mode optical fiber and cable.

  • G656 (Medium Dispersion Fiber - MDF): it is designed for local access and long haul fiber that performs well at 1460 nm and 1625 nm.

This kind of fiber was developed to support long-haul systems that use CWDM and DWDM transmission over the specified wavelength range and at the same time, it allows the easier deployment of CWDM in metropolitan areas, and increase the capacity of fiber in DWDM systems.

  • G657A: available in D, E, S, C and L5 wavebands. It can work in the whole working wavelength range of 1260-1625nm. With excellent bending performance and the technical requirements of geometric size are more accurate.

These fibers are intended to be compatible with the G.652 optical fibers but have differing bend sensitivity performance.

It is designed to allow fibers to bend, without affecting performance. This is achieved through an optical trench that reflects stray light back into the core, rather than it being lost in the cladding, enabling greater bending of the fiber.

G.657 as the latest standard for FTTH applications, along with G.652 is the most commonly used in last drop fiber networks.

REMEMBER: Choosing the right single-mode fiber for your network application is an important decision.

Here is a chart from:http://opticalfiberalsa.over-blog.com/2016/06/single-mode-fiber-standard-and-selection.html that explains more technically about the different types of these fiber optic cables and their divisions:

Singlemode type chart
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June 07, 2017 by Beyondtech Team

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