(a) Evolution of the signal wave field being pumped by forward and backward components of the pumping wave within a cavity of L = 14l₀ ≈ 3.32 μm. (b) Power evolution of the signal wave within a propagation distance of 3.32 μm for CPM pumping, single-pass pumping, and without pumping. (c) The output power of the signal wave varies with the input pumping power with cavity and without cavity, where the thresholds P_p are marked out for the OPA gain condition (P_s/P_s (0) = 1). (d) The output power of the signal wave varies with r₂ for the cases of r₁ = r_m, 0.99, and 0.96.