Specifications

1-3

Cisco ONS 15216 EDFA2/EDFA2-A Operations Guide, R2.4

July 2004

Chapter 1 Applications

1.3.2 Gain Flattening

• Constant Pump Current mode

• Constant Pump Power mode

1.3.2 Gain Flattening

Figure 1-2 illustrates the effect of the gain flattening filter in the ONS 15216 EDFA2. Fiber (a) in the

figure shows a set of channels with equal powers being input to a cascaded network of amplifiers that

produce vastly different power levels and optical signal-to-noise ratios (OSNR) at the output. In contrast,

fiber (b) shows how the EDFAs effectively reduce this effect by introducing a gain flattening filter within

each amplifier.

Figure 1-2 Gain Flattening Filter

1.3.3 Transient Suppression

Transients in the performance of optical amplifiers are inevitable whenever the number of signals, or the

relative power of signals, changes. The ONS 15216 EDFA2 uses transient suppression to reduce the

amount of time required by an amplifier to recover from a change. This indicates the suitability of the

amplifier for add/drop applications like those described earlier.

1.3.4 Low Noise

Whenever there is gain in an optical system, noise also occurs. The predominant source of noise in

EDFAs is amplified spontaneous emission (ASE). The ONS 15216 EDFA2 has a low noise figure.

1.3.5 Automatic Laser Shutdown

If automatic laser shutdown is enabled, when the input power (signal) goes below the loss of signal

value, the laser pumps are shut down until the input signal is restored. This option prevents ASE

(typically –3.5 dBm) from being present at the output during the loss of signal.

Gain

Flattening

Filter

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