Cisco Systems 15216 EDFA2 manual Constant Gain, Gain Flattening

Chapter 1 Applications

Key Features

F I N A L D R A F T - C I S C O C O N F I D E N T I A L

The ONS 15216 EDFA2 has the following key features:

•Adjustable constant gain of 13 to 22 dB

•Gain flattening < 2 dB (peak to valley)

•Transient suppression

•Low noise figure of < 7 dB at –5 dBm input

•Simple Network Management Protocol (SNMP) MIBs

•Transaction Language 1 (TL1)

1.3.1Constant Gain

Constant amplification (gain) per wavelength is important for ensuring that variations in power between channels at the receivers is minimized. As wavelengths are added/dropped from an optical fiber, small variations in gain between channels in a span can cause large variations in the power difference between channels at the receivers. The ONS 15216 EDFA2 enables bandwidth-on-demand services by guaranteeing that every wavelength is amplified by a value that can be set between 13 and 22 dB, no matter how many wavelengths are being amplified.

Constant gain is achieved using an automatic control circuit that adjusts pump power when changes in input power are detected. The ONS 15216 EDFA2 operates in Constant Gain Temperature Compensated mode by default, but since there may be applications where other operating modes may be required, the ONS 15216 EDFA2 can be set to operate in any one the following pump control modes:

•Constant Gain Temperature Compensated mode

•Constant Output Power mode

•Constant Pump Current mode

•Constant Pump Power mode

1.3.2Gain Flattening

Figure 1-3illustrates 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 1-3 Gain Flattening Filter

a

b

Gain

Flattening

Filter

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Cisco ONS 15216 EDFA2 Operations Guide

78-16033-01 1-3