A review paper by a research group from the Optoelectronics Research Centre at the University of Southampton in the UK summarizes their recent achievements in developing nonlinear optical devices for all-optical signal processing. They discuss achievements on optical signal processing using silicon-germanium and amorphous-silicon-based waveguides and on novel materials, such as silicon-rich silicon nitride and tantalum pentoxide.
In the paper “Nonlinear Silicon Photonic Signal Processing Devices for Future Optical Networks,” published in Applied Science, the researchers review the performance of four-wave mixing (FWM) wavelength conversion applied on complex signals such as Differential Phase Shift Keying (DPSK), Quadrature Phase Shift Keying (QPSK), 16-Quadrature Amplitude Modulation (QAM) and 64-QAM that dramatically enhance the telecom signal spectral efficiency, paving the way to next generation terabit all-optical networks.
The exponentially growing demand for bandwidth requires flexible solutions for the next generation optical networks. Nonlinear optical components have already been used in the past to address technical challenges, such as the need of wavelength transparent, reconfigurable all-optical components for signal processing scopes. And silicon-photonic nonlinear components are now sufficiently mature to provide low-cost, low-power all-optical signal processing components for the next-generation all-optical settings.
Now the group at Southhampton has reviewed such components and novel silicon-based materials to further improve the capabilities of these devices.
Impact on future terabit all-optical networks
“Next-generation optical networks will require flexible, reconfigurable, low-power and low-cost optical components to manipulate complex telecommunication signals,” predicts Dr Cosimo Lacava, the lead author of the paper. “The devices we have developed here at the ORC, in collaboration with our European partners, can process complex signals at very high bit rate — such as QAM signals at bit rate greater than 50 Gb/s — without the need of optical-electrical-optical transitions.” This would dramatically reducing the overall system complexity, and thus the cost of the telecom settings. Furthermore, “This would allow to impressively increase the bandwidth of the current optical communication networks and prepare the system for further improvements in the future,” adds Lacava.
Lacava and his colleagues are now working on the material side to study and find novel CMOS-compatible materials that can further reduce the power consumption and make future systems greener and more efficient.
Written by Sandra Henderson, research editor Novus Light Technologies Today