under default/amplifiers library/optical you can find the edfa amplifier. you will have to adjust the various properties to acheive a gain of 10db. If you press help you will find the equations that you will need to use. Solving Equation 1, Equation 2, and Equation 3 under stationary conditions allows you to determine the amplifier performance features. to make it simpler you can also use the edfa black box. the edfa black box allows you to simply choose the value of gain, power, etc instead of having to perform the calculations that would be required if you used the edfa.