Mamyshev 2R Regenerator - Principle of Operation and Design

Principle of Operation and Design

The Mamyshev regenerator can handle return-to-zero signals with ultrahigh data bit rates. Indeed, thanks to the quasi-instantaneous response of the nonlinear Kerr effect, this regenerator does not suffer from the finite recover time of some saturable absorbers.

The interest of the Mamyshev regenerator lies in its ability to regenerate simultaneously the 'ones' and 'zeros' bit of information.

The key effect affecting the pulse evolution in the regenerator is the self-phase modulation that broadens the spectrum in proportion to the intensity of the initial optical pulse. Combined with an output frequency offset OBPF, this constitutes an efficient ultrafast thresholder. In more details, low intensity pulses or noise do not broaden significantly and fall outside of the off-centered BPF and hence the output for the noisy 0's in the data stream are reduced to the zero floor. On the contrary, for the 1's data pulses the intensity is sufficiently strong to broaden the spectra by SPM, and a significant portion of the spectrum falls into the OBPF passband, leading to a generation of the output 1's pulse.

For a careful design of the regenerator and an appropriate combination of filter parameter (spectral offset and bandwidth) / fiber parameter (length, dispersion and nonlinearity values), a reduction of amplitude fluctuations can also be achieved, leading to power equalization of the pulse stream.

The modelling results for the 2R regenerator are shown with the article. In Figure 1, the upper panel shows regenerated pulse from the input (lower panel) for the Mamyshev 2R regenerator. Note how the noisy 1's pulses are boosted to same power levels in the output, while the 0's pulses are reduced to the noise floor.

An important property of a Mamyshev regenerator is its transfer fonction that links the output peak power to the input peak power. For an efficient operation and power equalization, this transfer function should exhibit a marked plateau at the 1's power level. Example of a transfer function is provided Figure 2.

The spectral operations of broadening, filtering and regeneration about the central wavelength are shown in Figure 3.

Note also that in the design of this nonlinear regenerator, care should be given to avoid the consequences of deleterious Brillouin backscattering as well as pulse to pulse interaction leading to patterning effects in the output sequence.