Page 190 - Optical Communications Essentials

Optical Amplifiers

180 Chapter Eleven

30
Unsaturated region
300 mA 3 dB
25 150 mA Saturation power
Fiber-to-fiber gain (dB) 20 100 mA Saturated region

15

10

5
-5 0 5 10 15
Amplifier output power (dBm)
Figure 11.4. Dependence of gain on input power for three different
bias conditions for a representative SOA. Definitions are illustrated
for saturated and unsaturated regions and saturation power.

Figure 11.5. Saturation power of a particular SOA at 300mA as a
function of wavelength.

power is about 10dBm. The saturation power varies with wavelength, as
Fig. 11.5 illustrates.
■ Gain bandwidth. The wavelength at which the SOA has a maximum gain can
be tailored to occur anywhere between about 1100 and 1700 nm by changing
the composition of the active InGaAsP material. As an example, Fig. 11.6
shows a typical gain versus wavelength characteristic for a device with a
peak gain of 25 dB at 1530 nm. The wavelength span over which the gain
decreases by less than 3 dB with respect to the maximum gain is known as
the gain bandwidth or the 3-dB optical bandwidth. In the example shown in
Fig. 11.6, the 3-dB optical bandwidth is 85 nm. Values of up to 100 nm can
be achieved.

Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)
Copyright © 2004 The McGraw-Hill Companies. All rights reserved.
Any use is subject to the Terms of Use as given at the website.