Channel addition/removal response in Raman fiber amplifiers: modeling and experimentation

Flat-Gain Fiber Raman Amplifiers Using Equally Spaced Pumps

“…We only consider the steady-state gain, as is appropriate when modeling long-haul systems. In networks that add and drop channels, transient gain would have to be considered as well [8], [9]. The pump-to-pump, pump-to-signal, and signal-to-signal Raman interactions are considered in the coupled equations (1) where is the number of pump waves, and is the number of signal waves.…”

Transient gain dynamics in saturated Raman amplifiers

“…We will closely follow the derivations for the counter-propagating pump. In this case both pump and signals are injected at z i = 0 and propagate at group velocity υ p and υ s in the positive z direction, with walk-off d ∼ = D(λ s − λ p ) dictated by the GVD parameter D. 6 Neglecting direct signal crosstalk, the solution at coordinate z 0 = z L of the propagation equations for the co-propagating pump configuration in the retarded frames is obtained from (2) as…”

“…Such transients can be numerically reproduced by solving the coupled time-dependent propagation equations for signals and pumps, and are connected to the signal-pump walk-off [5]. Simulation and experimental results with two WDM channels and multiple counter-propagating pumps were also reported in [6].…”

“…It is known that transient gain dynamics are present also in co-pumped Raman amplifiers, with transients occurring on a much faster time scale than in counter-pumped amplifiers [6,8]. We develop here a state-variable model also for the co-pumped case, which we use to predict the time constants of the transients.…”

Automatic laser shutdown implications for all optical data networks

“…For a modern optical amplifier, the typical total duration of the transient time arising from the addition or deletion of channels in a link is of order 100 µs or less [14]. This is also typically true for Raman fiber amplifiers [15]- [17]. The problem of false LOS due to amplifier transients will occur with the deletion of channels, because it is only in this case that any overshoot will result in a reduction of the power in the fiber being below the LOS threshold for 100 µs.…”