Amplification of advanced modulation formats with a semiconductor optical amplifier cascade

Abstract

The convergence of optical metro networks and access networks extends the area of network coverage, and therefore requires the use of optical amplifiers. For this purpose, semiconductor optical amplifiers (SOA) would be attractive, because they are broadband, can be centered between 1250 nm and 1600 nm, and because they are cheap in production and operation. We show that signals encoded with advanced modulation formats such as BPSK, QPSK, 8PSK, and 16QAM can be amplified by a cascade of at least four SOAs. This enables high-capacity paths with a capacity in the order of Tbit/s for converged metro-access networks.

Estimation of the Performance Improvement of Pre-Amplified PAM4 Systems When Using Multi-Section Semiconductor Optical Amplifiers

“…Without knowledge of the exact SOA gain saturation characteristics, the channels could be closer to the gain-peak of the SOA and therefore the saturation power would be lower such that different channels will experience a different saturation power. An experimental study for amplifying a single wavelength channel and two wavelength channel systems with only 150 GHz channel separation for various modulation formats (though PAM4 as not one of them) [9] showed one or two dB power penalty when amplifying two channels compared to the single channel scenario, and the simulation results here are in qualitative agreement those multi-channel penalties. .…”

“…We consider the SOA as a pre-amplifier, and typically SOA pre-amplifiers have moderate gains of 13 to 15 dB amplification [8][9][10][11] in order to avoid deleterious gain saturation. Selecting a device with a larger gain will only reduce the input optical power at which gain saturation occurs.…”

“…Secondly, SOAs are being given serious consideration to also play a role as pre-amplifiers for PAM4 signals as reach extenders or to overcome inevitable insertion losses of an optical switch as shown in Figure 1b [6,7]. Usually, SOAs suffer from a relatively high noise figure (NF) which limits the minimum signal power that can be reliably amplified to a few tens of µW; SOAs also suffer from low gain saturation power (the order of 10 mW) which distorts the amplified signal even when the average input signal power is of the order of hundreds of microwatts [8,9].…”

Low penalty, dual stage, broadband discrete Raman amplifier for high capacity WDM metro networks

“…While the long distance transmission demonstrated here confirms the low penalty due to intra-channel nonlinearity of these discrete Raman amplifiers, it is in short distance metro networks where capacity growth is currently greatest and we anticipate using higher order modulation formats such as DP-64-QAM in the near future [9]. Recent improvements in SOAs [10] could offer comparably high bandwidth in metro networks and in data centre applications, but the nonlinear penalty due to repeated SOA passes is still an issue [11] while the proven cascadability of discrete Raman amplifiers could make them an attractive choice for such links.…”

Self-Seeded RSOA-Fiber Cavity Lasers vs. ASE Spectrum-Sliced or Externally Seeded Transmitters—A Comparative Study

“…Then we calculated the Q 2 values for each transmitter scheme at various received input powers. We have been using Q 2 values rather than BER as a quality metric, because our dominant noise source is the RSOA ASE noise that acts as an almost ideal white Gaussian noise source for not-too-high input powers [40]. The black dashed lines in Figure 14 Figure 14.…”