This Recommendation describes a single-mode fibre with a
chromatic dispersion coefficient (absolute value) that is greater
than some non-zero value throughout the wavelengths larger than
1530 nm. This dispersion reduces the growth of non-linear effects
that can be particularly deleterious in dense wavelength division
multiplexing (DWDM) systems. At lower wavelengths, the dispersion
coefficient can cross zero, but chromatic dispersion coefficient
values at these wavelengths may be specified to support coarse
wavelength division multiplexing (CWDM) systems that do not have
significant impairments due to non-linear effects.
These fibres were originally intended for use at wavelengths in
a prescribed region between 1530 nm and 1565 nm. Provisions have
been made to support transmission at higher wavelengths of up to
1625 nm and lower wavelengths down to 1460 nm.
In clause 7, Tables 2 and 3 distinguish the two main families of
ITU-T G.655 fibre implementations that are supported by multiple
vendors. The G.655.A, G.655.B and G.655.C attributes tables can be
used to define other implementations. The G.655.A and G.655.B
attributes tables of the 2003 edition are not included in the
current version of this Recommendation.
The geometrical, optical, transmission and mechanical parameters
are described below in three categories of attributes:
• fibre attributes are those attributes that are retained
throughout cabling and installation;
• cable attributes that are recommended for cables as they are
• link attributes that are characteristics of concatenated
cables, describing estimation methods of system interface
parameters based on measurements, modelling, or other
considerations. Information for link attributes and system design
are in Appendix I.
This Recommendation, and the different performance categories
found in the tables of clause 7, is intended to support the
following related system Recommendations:
• ITU-T G.691;
• ITU-T G.692;
• ITU-T G.693;
• ITU-T G.695;
• ITU-T G.696.1;
• ITU-T G.698.1;
• ITU-T G.957
• ITU-T G.959.1.
This Recommendation contains a combination of fibre designs able
to cover a broad spectrum of applications. Some re-arrangement
might be considered in the future. However, the system
compatibility of fibres with different characteristics is not
proved and, in general, their simultaneous use in one system might
be questioned and should be agreed in advance between the user and
The meaning of the terms used in this Recommendation and the
guidelines to be followed in the measurement to verify the various
characteristics are given in [ITU-T G.650.1] and [ITU-T G.650.2].
The characteristics of this fibre, including the definitions of the
relevant parameters, their test methods and relevant values, will
be refined as studies and experience progress.
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