EDFA Gain Modulation

Tool Used: OptSim

This example demonstrates modulation of a pump’s optical power to produce gain modulation in an EDFA, and is based on the parameters and results in [1]. The simulation uses Transient simulation mode in OptSim.

A 980 nm pump and 1530 nm signal are launched into a 10.5 m EDFA, modeled via the Compact Transient EDFA model. The input signal power is fixed, while the pump power is modulated as

Compact Transient EDFA model
where Ppo is the average pump power, mp is the modulation index, f_mod is the modulation frequency, and t is time.

Figure 2 shows the modulated 980 nm pump and constant 1530 nm signal inputs to the EDFA (analogous to Figure 4 from [1]), plotted using Tplotter1, while Figure 3 shows the corresponding EDFA outputs (analogous to Figure 5 from [1]), plotted using TPlotter2. As can be seen, the average powers gradually approach steady state, with the pump still showing modulation, and the signal also showing very slight modulation as well due to the modulated EDFA gain.

Note that the above approach for modulating the pump power can be extended to other expressions, including random power variations. 

Schematic demonstrating EDFA dynamic response to a modulated pump input.

Figure 1. Schematic demonstrating EDFA dynamic response to a modulated pump input.

EDFA input signals, showing modulated pump at 980 nm

Figure 2. EDFA input signals, showing modulated pump at 980 nm.

EDFA outputs, showing evolution towards steady state

Figure 3. EDFA outputs, showing evolution towards steady state, modulated output pump, and slight modulation of output signal.

Reference

1.       S. Novak and R. Gieske, “Simulink model for EDFA gain dynamics applied to gain modulation,” Journal of Lightwave Technology, vol. 20, no. 6, pp. 986-992, June 2002.