388
10 Wavelength Division Multiplexing (WDM)
for WDM. This document specifies selecting the channels from a grid of frequencies referenced to 193.100 THz (1552.524 nm) and spacing them 100 GHz (about
0.8 nm at 1550 nm) apart. Suggested alternative spacings in G.692 include 50 GHz
and 200 GHz, which correspond to spectral widths of 0.4 and 1.6 nm, respectively,
at 1550 nm.
Historically the term dense WDM (DWDM) generally referred to small wavelength separations. The ITU-T Recommendation G.694.1 is aimed specifically at
DWDM. This document specifies WDM operation in the S-, C-, and L-bands for
high-quality, high-rate metro area network (MAN) and wide area network (WAN)
services. It calls for narrow frequency spacings of 100–12.5 GHz (or, equivalently, 0.8
to 0.1 nm at 1550 nm). This implementation requires the use of stable, high-quality,
temperature-controlled and wavelength-controlled (frequency-locked) laser diode
light sources. For example, the wavelength-drift tolerances for 25-GHz channels are
±0.02 nm.
Table 10.1 lists part of the ITU-T G.694.1 dense WDM frequency grid for 100GHz and 50-GHz spacings in the L- and C-bands. The column labeled “50-GHz
offset” means that for the 50-GHz grid, one interleaves these 50-GHz values with
the 100-GHz spacings. For example, the 50-GHz channels in the L-band would be
at 186.00, 186.05, 186.10 THz, and so on. Note that when the frequency spacing is
uniform, the wavelengths are not spaced uniformly because of the relationship given
in Eq. (10.1).
To designate which C-band channel is under consideration in 100-GHz applications, the ITU-T uses a channel numbering convention. For this, the frequency
19 N.M THz is designated as ITU channel number NM. For example, the frequency
194.3 THz is ITU channel 43.
Table 10.1 Portion of the ITU-T G.694.1 dense WDM grid for 100- and 50-GHz spacings in the
L- and C-bands
L-band
C-band
100-GHz
50-GHz offset
100-GHz
50-GHz offset
THz
nm
THz
nm
THz
nm
THz
nm
186.00
1611.79 186.05
1611.35 191.00
1569.59 191.05
1569.18
186.10
1610.92 186.15
1610.49 191.10
1568.77 191.15
1568.36
186.20
1610.06 186.25
1609.62 191.20
1576.95 191.25
1567.54
186.30
1609.19 186.35
1608.76 191.30
1567.13 191.35
1566.72
186.40
1608.33 186.45
1607.90 191.40
1566.31 191.45
1565.90
186.50
1607.47 186.55
1607.04 191.50
1565.50 191.55
1565.09
186.60
1606.60 186.65
1606.17 191.60
1564.68 191.65
1564.27
186.70
1605.74 186.75
1605.31 191.70
1563.86 191.75
1563.45
186.80
1604.88 186.85
1604.46 191.80
1563.05 191.85
1562.64
186.90
1604.03 186.95
1603.60 191.90
1562.23 191.95
1561.83
10 Wavelength Division Multiplexing (WDM)
for WDM. This document specifies selecting the channels from a grid of frequencies referenced to 193.100 THz (1552.524 nm) and spacing them 100 GHz (about
0.8 nm at 1550 nm) apart. Suggested alternative spacings in G.692 include 50 GHz
and 200 GHz, which correspond to spectral widths of 0.4 and 1.6 nm, respectively,
at 1550 nm.
Historically the term dense WDM (DWDM) generally referred to small wavelength separations. The ITU-T Recommendation G.694.1 is aimed specifically at
DWDM. This document specifies WDM operation in the S-, C-, and L-bands for
high-quality, high-rate metro area network (MAN) and wide area network (WAN)
services. It calls for narrow frequency spacings of 100–12.5 GHz (or, equivalently, 0.8
to 0.1 nm at 1550 nm). This implementation requires the use of stable, high-quality,
temperature-controlled and wavelength-controlled (frequency-locked) laser diode
light sources. For example, the wavelength-drift tolerances for 25-GHz channels are
±0.02 nm.
Table 10.1 lists part of the ITU-T G.694.1 dense WDM frequency grid for 100GHz and 50-GHz spacings in the L- and C-bands. The column labeled “50-GHz
offset” means that for the 50-GHz grid, one interleaves these 50-GHz values with
the 100-GHz spacings. For example, the 50-GHz channels in the L-band would be
at 186.00, 186.05, 186.10 THz, and so on. Note that when the frequency spacing is
uniform, the wavelengths are not spaced uniformly because of the relationship given
in Eq. (10.1).
To designate which C-band channel is under consideration in 100-GHz applications, the ITU-T uses a channel numbering convention. For this, the frequency
19 N.M THz is designated as ITU channel number NM. For example, the frequency
194.3 THz is ITU channel 43.
Table 10.1 Portion of the ITU-T G.694.1 dense WDM grid for 100- and 50-GHz spacings in the
L- and C-bands
L-band
C-band
100-GHz
50-GHz offset
100-GHz
50-GHz offset
THz
nm
THz
nm
THz
nm
THz
nm
186.00
1611.79 186.05
1611.35 191.00
1569.59 191.05
1569.18
186.10
1610.92 186.15
1610.49 191.10
1568.77 191.15
1568.36
186.20
1610.06 186.25
1609.62 191.20
1576.95 191.25
1567.54
186.30
1609.19 186.35
1608.76 191.30
1567.13 191.35
1566.72
186.40
1608.33 186.45
1607.90 191.40
1566.31 191.45
1565.90
186.50
1607.47 186.55
1607.04 191.50
1565.50 191.55
1565.09
186.60
1606.60 186.65
1606.17 191.60
1564.68 191.65
1564.27
186.70
1605.74 186.75
1605.31 191.70
1563.86 191.75
1563.45
186.80
1604.88 186.85
1604.46 191.80
1563.05 191.85
1562.64
186.90
1604.03 186.95
1603.60 191.90
1562.23 191.95
1561.83