Fig. 1. Working principle of third-order Raman fiber amplifier

Fig. 2. Working principle of third-order Raman fiber amplifier without second-order pump seed light

Fig. 3. Experiment setup with only pumps as input

Fig. 4. The output spectrum when only third-order pump light is input

Fig. 5. The output spectrum when first-order and third-order pump lights are input

Fig. 6. The relationship between the power of pumps and the input power of the third-order pump when only the third-order pump is input

Fig. 7. The relationship between the power of pumps and the input power of the third-order pump when first-order pump and third-order pump are input

Fig. 8. The influence of second-order pump seed light on the output power of first-order pump light

Fig. 9. (a) Block diagram and (b) physical diagram of the experiment setup

Fig. 10. The input optical spectrum

Fig. 11. Comparison of output signal powers

Fig. 12. Comparison of output signal OSNR