Light-light switching typically requires strong nonlinearity where intense laser fields route and direct data flows of weak power, leading to a high power consumption that limits its practical use. Here we report an experimental demonstration of a metawaveguide that operates exactly in the opposite way in a linear regime, where an intense laser field is interferometrically manipulated on demand by a weak control beam with a modulation extinction ratio up to approximately 60 dB. This asymmetric control results from operating near an exceptional point of the scattering matrix, which gives rise to intrinsic asymmetric reflections of the metawaveguide through delicate interplay between index and absorption. The designed metawaveguide promises low-power interferometric light-light switching for the next generation of optical devices and networks. DOI: 10.1103/PhysRevLett.117.193901 Effective light-light switching promises optical information processing, which has been a long-standing driving force for high-speed and energy-efficient optical networks. Strong optical modulations are initiated in nonlinear optical media by intense laser fields to enable switching of a weak signal, for example, intensity modulation of light by light has been demonstrated based on the all-optical Kerr effect [1][2][3][4][5][6]. Nevertheless, the high power requirement for the intense control or pump light becomes a significant barrier for practical applications. While cavity quantum electrodynamics displays nonlinear optical effects on a few-photon level [7,8], its application as a robust optical element operating in the classical regime remains still unclear. On the other hand, a recent pioneering investigation of exploiting photonics absorption offered a unique linear scheme to efficiently control light by light utilizing mutually coherent interaction of light beams and absorbing matters [9,10], by which coherent perfect absorption (CPA) was demonstrated [11][12][13][14]. While this linear strategy reduces the power requirement, the control beam still has a similar amount of power as the actual source signal in these previous works, due to the rather symmetric optical scatterings in the optical implementations.The recent emergence of non-Hermitian photonic metamaterials offers a new paradigm to explore nanophotonics and metamaterials research in the entire complex dielectric permittivity plane, based on parity-time (PT) symmetry [15][16][17][18][19][20]. Attractive physical phenomena including phase transitions and exceptional points are emulated with photonics, consequently, leading to novel effective manipulation of cavity lasing modes [21][22][23][24][25][26] and unidirectional light transport [27][28][29][30][31][32]. Here, we will show a unique metawaveguide of potential for on-demand control of interferometric light-light switching can be realized through non-Hermitian metamaterial explorations.An intriguing characteristic of non-Hermitian photonic metamaterials is their intrinsic asymmetry near an exceptional point. For PT sym...

Optical transmission systems with high spectral efficiency require accurate quality of transmission estimation for optical channel provisioning. However, the wavelength-dependent gain effects of erbium-doped fiber amplifiers (EDFAs) complicate precise optical channel power prediction and low-margin operation. In this work, we examine supervised machine learning methods using multiple artificial neural networks (ANNs) to build models for gain spectra prediction of optical transmission line EDFAs under different operating conditions. Channel-loading configurations and channel input power spectra are used as an a posteriori knowledge data feature for model training. In a hybrid learning approach, estimated gain spectra calculated by an analytical model are added as an a priori input data feature to further improve the EDFA ANN model performance in terms of prediction accuracy, training time, and quantity of training data. Using these methods, the root mean square error and maximum absolute error of the predicted channel output power can be as low as 0.144 dB and 1.6 dB, respectively.

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We demonstrate practical software emulation of a software-defined, packetoptical network. Our emulator, Mininet-Optical, models the physical, data plane and control plane behavior, under control of the ONOS SDN controller.

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We investigate dynamic network resource allocation using software-defined networking optical controller with software-defined radios on the COSMOS testbed. 10 Gb/s capacity, deterministic low latency are maintained through user equipment wireless handover via optical switching.

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