An erbium-doped fibre nonlinear coupler with coupling ratios controlled by pump power

Influence of bidirectional pumping in high-power EDFA on single-channel, multichannel and pulsed signal amplification

“…Hence n 2 may be expected to vary differently in different pumping schemes. This concept of enhanced optical nonlinearities due to absorption resonance is widely used in applications involving nonlinear fibre couplers [33]. A refractive index change of the order of 10 −6 at a signal wavelength of 1550 nm and a pump wavelength of 980 nm is reported in one such work [11], which corresponds to an n 2 , four orders of magnitude larger than the conventional value.…”

Stabilization of solitons in PT models with supersymmetry by periodic management

“…In particular, the P T symmetry can be realized in this dual-core system by balancing the gain and loss in the active and passive linearly-coupled cores. This implies that both cores can be made of a doped lossy material, while the dopant atoms, if pumped externally, may add a linear gain to the system [24]. Then, if the external pump is applied to a single core, it may supply the gain overcompensating the intrinsic loss of this core, so as the net gain provides the P T balance with the other core, that remains lossy.…”

All-optical logical gates based on pump-induced resonant nonlinearity in an erbium-doped fiber coupler

“…The resonant nonlinearity, yielded by the optical transitions between 4 I 15∕2 states and 4 I 13∕2 states in Er 3 , leads to the refractive index change [8]. The resonant transition of Er 3 from the excited state to the ground state can also cause complex propagation constant change, in which the real part is related to the change of refractive index n, and the imaginary part corresponds to the change of gain coefficient g [10]. According to the resonant nonlinearity model that is mentioned above, the coupling mode equations are expressed as…”

“…On the basis of the three-level model of Er 3 ions, the refractive index change and the gain coefficient change due to pumping can be expressed as [8,10,21] Δn…”

“…The propagation constant is changed because of the gain and the resonant nonlinearity caused by the pump. Both the change of refractive index and gain coefficient in the coupling region are regarded as the real and imaginary parts of the variation of the complex propagation constant [10]. All-optical logical operations using the optical Kerr effect as a switching mechanism have been intensively studied in theory and experiment [11][12][13][14][15][16], but the threshold power of the pump is very large [17].…”