Recommendation G.957 (06/99)
12
6.3 Optical
path
To ensure system performance for each of the applications considered in Table 1, it is necessary to
specify attenuation and dispersion characteristics of the optical path
between reference points S
and R.
6.3.1 Attenuation
In this
Recommendation, attenuation for each application is specified as a range, characteristic of the
broad application distances indicated in Table 1. However, to provide flexibility in
implementing
transverse compatible systems, this Recommendation recognizes some overlap between attenuation
ranges between the intra-office applications and the short-haul inter-office applications and between
the short-haul inter-office applications and the long-haul inter-office applications. Attenuation
specifications are assumed to be worst-case values including losses due to splices, connectors,
optical attenuators (if used) or other
passive optical devices, and any additional cable margin to cover
allowances for:
1)
future modifications to the cable configuration (additional splices,
increased cable lengths,
etc.);
2)
fibre cable performance variations due to environmental factors; and
3)
degradation of any connector, optical attenuators (if used) or other passive optical devices
between
points S and R, when provided.
6.3.2 Dispersion
Systems considered limited by dispersion have maximum values of dispersion (ps/nm) specified in
Tables 2 to 4. These values are consistent with the maximum optical path penalties specified
(i.e. 2 dB for L-16.2, 1 dB for all other applications). They take into account the specified transmitter
type, and the fibre dispersion coefficient over the operating wavelength range.
Systems considered limited by attenuation do not have maximum dispersion
values specified and are
indicated in Tables 2 to 4 with the entry NA (not applicable).
Chia sẻ với bạn bè của bạn: 
