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Active Optical Components
168 Chapter Ten
Figure 10.5. Three methods for adjusting the wave-
length of a tunable Bragg grating.
distance variation can be achieved by any of the three methods described above
for tunable gratings.
Table 10.2 lists some representative performance parameters of a tunable
optical filter (see Sec. 9.4 for definitions of some of the filter terms). Applications
of these devices include gain-tilt monitoring in optical fiber amplifiers, optical
performance monitoring in central offices, channel selection at the receive side
of a WDM link, and suppression of amplified spontaneous emission (ASE) noise
in optical amplifiers (see Chap. 11).
10.5. Dynamic Gain Equalizers
A dynamic gain equalizer (DGE) is used to reduce the attenuation of the indivi-
dual wavelengths within a spectral band. These devices also are called dynamic
channel equalizers (DCEs) or dynamic spectral equalizers. The function of a DGE
is equivalent to filtering out individual wavelengths and equalizing them on a
channel-by-channel basis. Their applications include flattening the nonlinear
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