All-optical Routing Research Articles

Design and testing of an optical routing device with reconfigurable optical add/drop multiplexer and interleaver functions

A multifunction all-optical routing device for a dynamic network is presented. The proposed routing device consists of two arrayed waveguide gratings (AWGs), 12 optical circulators, and six tunable fiber Bragg gratings (TFBGs) to realize the functions of all-optical multichannel reconfigurable optical add/drop multiplexer (ROADM) and optical wavelength interleaver. The AWGs have the characteristics of wavelength cycling of light. So even if there is no additional optical architecture in the proposed optical device, it can have the function of an optical interleaver. Both ROADM and optical interleaver are the keys to enable the modern optical communication services and support the remote configuration of optical paths and the reconfiguration of network topologies. The experimental data show that the functions of add/drop and wavelength interleaver can be implemented. Three dense wavelength division multiplexing (DWDM) channels are used to evaluate the performance of ROADM of the proposed routing device. The results of this study demonstrated the feasibility of this routing device for the DWDM networks.

Attosecond soliton shaping through dispersion tailoring technique in a monomode optical fiber

Analytical attosecond multi-soliton solutions for the variable coefficient sixth order nonlinear Schrödinger equation is investigated by means of Darboux transformation technique. Through the tailoring of group velocity dispersion (GVD) coefficient of inhomogeneous optical fibers, various abundant soliton structures are constructed. As few examples, V-shaped soliton, S-shaped soliton, dromion structure and parabolic soliton are attained by modulating appropriate GVD parameters in an inhomogeneous monomode optical fiber. Moreover, for the first time, switching behavior of attosecond soliton have been achieved through dispersion management. Soliton control offers novel intangible opportunities for all-optical shaping, switching and routing which might be of potential applications in the design of ultrafast optical switches and understanding the essential role of variable coefficients.

All-optical photon switching, router and amplifier using a passive-active optomechanical system

We propose a feasible and flexible scheme to realize all-optical photon switching, router and amplifier by using a passive-active optomechanical system consisting of a passive cavity, an active cavity and a common movable membrane oscillator. Due to the cooperation between the gain effect of the active cavity and the interference effect between the probe fields, some novel phenomena arise, such as the frequency-independent perfect reflection first proposed in this paper, controllable photon routing, tunable fast and slow lights and so on. Based on the results, a photon switching of absorption-amplification and fast-slow-light transitions, and a photon router with controllable direction and intensity can be realized by adjusting relevant parameters such as the strengths of control fields and the relative phase between probe fields. Such a scheme may provide a promising platform for controllable photon transport and photonic device fabrication.

All-Optical Switching and Routing with a Nonlinear Metamaterial

We report the dynamic control characteristics of electromagnetic wave propagation in a nonlinear metamaterial by an applied electric field, which is constructed by an array of metallic nanowires embedded into a nonlinear dielectric. Numerical results show that the composite structure can appear three kinds of interesting interconversion characteristics among positive refraction, negative refraction, and cut-off states by adjusting the intensity of the applied electric field. Consequently, we can switch all-optically light states between the total reflection state (OFF state) and the total transmission state (ON state), as well as control light propagation route dynamically. Moreover, we also elaborate on the dependency of the refraction angles of energy flow and wave vector, and Brewster angle on the applied electric field and the orientation angle φ. These properties open up an avenue for potential applications of nonlinear metamaterials in nanophotonic devices such as all-optical switches, routers, and wave cut-off devices.

Tunable photonic band gaps and optical nonreciprocity by an RF-driving ladder-type system in moving optical lattice

We investigate photonic transport properties of the 1D moving optical lattices filled with vast cold atoms driven into a four-level ladder-type system and obtain dynamically controlled photonic bandgaps and optical nonreciprocity. It is found that the two obvious optical nonreciprocity can be generated at two well-developed photonic bandgaps based on double dark states in the presence of a radio-frequency field. However, when the radio-frequency field is absence, the only one induced photonic bandgaps with distinguishing optical nonreciprocity can be opened up via single dark state. Dynamic control of the induced photonic bandgaps and optical nonreciprocity could be exploited to achieve all-optical diodes and routing for quantum information networks.

Curved optical solitons subject to transverse acceleration in reorientational soft matter

We demonstrate that optical spatial solitons with non-rectilinear trajectories can be made to propagate in a uniaxial dielectric with a transversely modulated orientation of the optic axis. Exploiting the reorientational nonlinearity of nematic liquid crystals and imposing a linear variation of the background alignment of the molecular director, we observe solitons whose trajectories have either a monotonic or a non-monotonic curvature in the observation plane of propagation, depending on either the synergistic or counteracting roles of wavefront distortion and birefringent walk-off, respectively. The observed effect is well modelled in the weakly nonlinear regime using momentum conservation of the self-collimated beams in the presence of the spatial nonlocality of the medium response. Since reorientational solitons can act as passive waveguides for other weak optical signals, these results introduce a wealth of possibilities for all-optical signal routing and light-induced photonic interconnects.

All-optical tree-based greedy router using optical logic gates and optical flip-flops

Due to ever-increasing throughput demands, the lookup in conventional IP routers based on longest prefix matching is becoming a bottleneck. Additionally, the scalability of current routing protocols is limited by the size of the routing tables. Geometric greedy routing is an alternative to IP routing which replaces longest prefix matching with a simple calculation employing only local information for packet forwarding. For the first time, in this paper we propose a novel and truly all-optical geometric greedy router based on optical logic gates and optical flip-flops. The circuit of the router is constructed through the interconnection of SOAs and directional couplers. The successful functionality of the proposed router is verified through simulation. The circuit enables high data rate throughput.

Photoimprinted Controllable Fano Resonance in the Terahertz Regime

The emergence of metamaterials, including the recently proposed metasurfaces, provides unprecedented opportunities in the manipulation as well as the generation of terahertz (THz) waves. Various actively controllable THz devices such as optical switches and phase modulators have been achieved by incorporating external-stimuli-responsive media (typically semiconductors) in the configurations. Compared to predesigned metallic-resonator-based metamaterials, photoimprinted photonic structures offer us an all-optical route toward reconfigurable functionalities with superior flexibility. Here, we propose to photoimprint some specific patterns on a thin film of semiconductor to excite Fano-like resonances, which result from the coupling between dark and bright elements. Experimental measurements, performed with THz time-domain spectroscopy, demonstrate counterintuitive tunable deep features in extinction spectra positioned around the expected resonance frequency. Our simulations are in excellent agreement with t...

Electromagnetically induced 2D grating via refractive index enhancement in a far-off resonant system

We propose a scheme for electromagnetically induced 2D grating in a mixture of two three-level Λ systems driven by two pairs of far-detuned coherent standing-wave fields. The key idea, which has been used to achieve the refractive index enhancement with vanishing absorption, is to induce two Raman resonances for the probe field, and their strength can be tuned via the two-photon detunings and the intensity of coupling field. By manipulating the absorption and gain properties of these two Raman resonances, absorption-phase grating, phase grating and gain-phase grating which effectively diffract a probe field into high-order directions can be formed in the atoms with the help of standing-wave pattern coherent fields. The diffracting power of the presented gratings strongly depends on the two-photon resonance condition and amplitude of coherent fields, hence the gratings can be used as all-optical multi-channel splitters or all-optical router in optical networking and communication.

Electromagnetically induced two-dimensional grating assisted by incoherent pump

We propose a scheme for realizing electromagnetically induced two-dimensional grating in a double-Λ system driven simultaneously by a coherent field and an incoherent pump field. In such an atomic configuration, the absorption is suppressed owing to the incoherent pumping process and the probe can be even amplified, while the refractivity is mainly attributed to the dynamically induced coherence. With the help of a standing-wave pattern coherent field, we obtain periodically modulated refractive index without or with gain, and therefore phase grating or gain-phase grating which diffracts a probe light into high-order direction efficiently can be formed in the medium via appropriate manipulation of the system parameters. The diffraction efficiency attainable by the present gratings can be controlled by tuning the coherent field intensity or the interaction length. Hence, the two-dimensional grating can be utilized as all-optical splitter or router in optical networking and communication.

Bistable Beam Propagation in Liquid Crystals

Light-controlling-light is one of the most advanced paradigms in optical signal processing, including light-induced waveguides as well as all-optical switching and routing. Other fundamental aspects of all-optical processing are optical memories and sequential elements, which require responses depending on the evolution history of the system, such as the hysteresis stemming from optical multistability. Hereby, we report on optical bistability and hysteresis in cavityless geometries and in the presence of self-localized beams, i.e., spatial optical solitons, exploiting the nonlocal reorientational nonlinearity of nematic liquid crystals (NLC). When the optic axis of NLC is initially orthogonal to the applied electric field, the molecular dipoles start to rotate above a threshold named after the Freedericksz transition, the latter being usually of the second order. Here, we show that such transition become of the first order via the intrinsic feedback provided by self-focusing, in turn leading to the appearance of a hysteresis loop between diffracting and self-confined beams. We report on hysteresis of the beam size versus input power, as well as hysteresis versus applied voltage at a fixed beam power. Our findings introduce a novel kind of cavity-less optical bistability with propagating light beams and disclose a novel approach to information storage based on light self-localization.

Distance-Adaptive Spectrum Resource Allocation Using Subtree Scheme for All-Optical Multicasting in Elastic Optical Networks

We propose and investigate a subtree scheme for all-optical multicast routing, modulation level and spectrum allocation (AOM-RMSA) in elastic optical networks. A multicast request is accommodated by several light-trees and each light-tree covers only a part of the destination set. We assume that all nodes are multicast capable and investigate the subtree scheme over the single light-tree scheme for the AOM-RMSA problem under both static and dynamic traffic scenarios. In the static scenario, we formulate an integer linear programming model to obtain the optimal solution. Then, we propose two time-efficient heuristic algorithms that construct subtrees according to the link-sharing ratio between the paths from source to two distinct destinations. The proposed algorithms improve the spectrum utilization by building subtrees that have smaller tree-spanning size and adopt higher level modulation formats. They have also effectively reduced the blocking probability compared to single light-tree schemes.

Two-dimensional gain cross-grating based on spatial modulation of active Raman gain**Project supported by the National Natural Science Foundation of China (Grant Nos. 11274112 and 11347133).

Based on the spatial modulation of active Raman gain, a two-dimensional gain cross-grating is theoretically proposed. As the probe field propagates along the z direction and passes through the intersectant region of the two orthogonal standing-wave fields in the x–y plane, it can be effectively diffracted into the high-order directions, and the zero-order diffraction intensity is amplified at the same time. In comparison with the two-dimensional electromagnetically induced cross-grating based on electromagnetically induced transparency, the two-dimensional gain cross-grating has much higher diffraction intensities in the first-order and the high-order directions. Hence, it is more suitable to be utilized as all-optical switching and routing in optical networking and communication.

Multiport InP monolithically integrated all-optical wavelength router.

An indium phosphide-based monolithically integrated wavelength router is demonstrated in this Letter. The wavelength router has four input ports and four output ports, which integrate four wavelength converters and a 4×4 arrayed-waveguide grating router. Each wavelength converter is achieved based on cross-gain modulation and cross-phase modulation effects in a semiconductor optical amplifier. Error-free wavelength switching for a non-return-to-zero 2³¹-1 ps eudorandom binary sequence at 40 Gb/s data rate is performed. Both 1×4 and 3×1 all-optical routing functions of this chip are demonstrated for the first time with power penalties as low as 3.2 dB.

Optical Bloch oscillations and Zener tunneling of Airy beams in ionic-type photonic lattices.

We report on the existence of optical Bloch oscillations (OBOs) and Zener tunneling (ZT) of Airy beams in ionic-type photonic lattices with a refractive index ramp. Different from their counterparts in uniform lattices, Airy beams undergoing OBOs show an alternatively switched concave and convex trajectory as well as a periodical revival of input beam profiles. Moreover, the ionic-type photonic lattice established in photorefractive crystal exhibits a reconfigurable lattice structure, which provides a flexible way to tune the amplitude and period of the OBOs. Remarkably, it is demonstrated that the band gap of the lattice can be readily controlled by rotating the lattice inducing beam, which forces the ZT rate to follow two significant different decay curves amidst decreasing index gradient. Our results open up new possibilities for all-optical switching, routing and manipulation of Airy beams.

Crosstalk analysis of ring resonator switches for all-optical routing.

Optical switches based on ring resonator cavities were fabricated by a silicon photonics foundry process and analyzed for optical crosstalk at various data rates and channel spacings. These devices were compared to commercial bandpass filters and at 20Gb/s, 0.5dB power penalty is observed due to spectral filtering for bit error ratio threshold of 1 × 10-9. Concurrent modulation at 20Gb/s with a channel spacing as narrow as 40GHz shows error-free transmission with 1dB power penalty as compared to wider channel spacing for the ring-based switch.

V-shaped dark solitons in inhomogeneous optical fibers

Soliton control offers novel conceptual opportunities for all-optical shaping, switching and routing of optical signals encoded in soliton formats. In this paper, V-shaped dark solitons propagation in inhomogeneous optical fibers are investigated to carry out soliton control. Analytic dark soliton solutions for the variable coefficient nonlinear Schrödinger equation are obtained with the Hirota method. The group velocity dispersion coefficient of inhomogeneous optical fibers is chosen to be the tanh function, and the influences of corresponding parameters are analyzed. Results might be of potential applications in the design of all optical switches and pulse signal converters in ultra-fast optics.

Ultrafast Thermal Nonlinearity.

Third order nonlinear optical phenomena explored in the last half century have been predicted to find wide range of applications in many walks of life, such as all-optical switching, routing, and others, yet this promise has not been fulfilled primarily because the strength of nonlinear effects is too low when they are to occur on the picosecond scale required in today’s signal processing applications. The strongest of the third-order nonlinearities, engendered by thermal effects, is considered to be too slow for the above applications. In this work we show that when optical fields are concentrated into the volumes on the scale of few tens of nanometers, the speed of the thermo-optical effects approaches picosecond scale. Such a sub-diffraction limit concentration of field can be accomplished with the use of plasmonic effects in metal nanoparticles impregnating the thermo-optic dielectric (e.g. amorphous Si) and leads to phase shifts sufficient for all optical switching on ultrafast scale.

A novel single control all-optical switching and routing in nonlinear photonic crystals

A novel simple control all-optical switching and routing mechanism using two nonlinear photonic crystal (PC) cavities and a T-branch waveguide has been presented. It has been shown that using a single control signal, the input power can be switched with a high-contrast ratio and routed to any of the two output ports. The performance of the proposed device has been investigated through the use of temporal coupled-mode theory (CMT) and two-dimensional (2D) nonlinear finite-difference time-domain (FDTD) simulations in PCs of square lattice.

All-optical router at single-photon level by interference

The realization of the all-optical router with multiple input ports and output ports will have direct application to achieve the quantum network. We present a scheme of all-optical routing of coherent-state photons in a waveguide-cavity coupled system. Our router has four input ports and four output ports. The routing of photons is based on the interference. The outcomes show that the transport of the coherent-state photons injected through any input port can be controlled by the phases of the coherent-state photons injected through other input ports. This control can be realized at the single-photon level and requires no additional control fields. Therefore, the all-optical routing at single-photon level can be achieved.