Hi, I am using double-clad LMA-YDF fiber which has Cladding Absorption 4.80 dB/m near 976 nm. How I can predict the optimum fiber length of the amplifier while my seed signal is 100 mW and pump diode is 9 W at 976 nm? Please suggest some reference.
In this case (large input signal) I would use simply the 13 dB rule of thumb (it optimize the power conversion efficiency). Hence the fiber should be around 2.7 m long. Special coiling method would be beneficial too, e.g., figure-eight or kidney shape coil, see more details here: https://www.researchgate.net/publication/283240396_Numerical_Modeling_of_Pump_Absorption_in_Coiled_and_Twisted_Double-Clad_Fibers
Article Numerical Modeling of Pump Absorption in Coiled and Twisted ...