Yiyuan Xie

Crosstalk noise and bit error rate analysis for optical network-on-chip

Crosstalk noise is an intrinsic characteristic of photonic devices used by optical networks-on-chip (ONoCs) as well as a potential issue. For the first time, this paper analyzed and modeled the crosstalk noise, signal-to-noise ratio (SNR), and bit error rate (BER) of optical routers and ONoCs. The analytical models for crosstalk noise, minimum SNR, and maximum BER in mesh-based ONoCs are presented. An automated crosstalk analyzer for optical routers is developed. We find that crosstalk noise significantly limits the scalability of ONoCs. For example, due to crosstalk noise, the maximum BER is 10−3 on the 8×8 mesh-based ONoC using an optimized crossbar-based optical router. To achieve the BER of 10−9 for reliable transmissions, the maximum ONoC size is 6×6. A novel compact high-SNR optical router is proposed to improve the maximum ONoC size to 8×8.

Formal Worst-Case Analysis of Crosstalk Noise in Mesh-Based Optical Networks-on-Chip

Crosstalk noise is an intrinsic characteristic as well as a potential issue of photonic devices. In large scale optical networks-on-chips (ONoCs), crosstalk noise could cause severe performance degradation and prevent ONoC from communicating properly. The novel contribution of this paper is the systematical modeling and analysis of the crosstalk noise and the signal-to-noise ratio (SNR) of optical routers and mesh-based ONoCs using a formal method. Formal analytical models for the worst-case crosstalk noise and minimum SNR in mesh-based ONoCs are presented. The crosstalk analysis is performed at device, router, and network levels. A general 5 × 5 optical router model is proposed for router level analysis. The minimum SNR optical link candidates, which constrain the scalability of mesh-based ONoCs, are identified. It is also shown that symmetric mesh-based ONoCs have the best SNR performance. The presented formal analyses can be easily applied to other optical routers and mesh-based ONoCs. Finally, we present case studies of mesh-based ONoCs using the optimized crossbar and Crux optical routers to evaluate the proposed formal method. We find that crosstalk noise can significantly limit the scalability of mesh-based ONoCs. For example, when the mesh-based ONoC size, using optimized crossbar, is larger than 8 × 8, the optical signal power is smaller than the crosstalk noise power; when the network size is 16 × 16 and the input power is 0 dBm, in the worst-case, the signal power is -24.9 dBm and the crosstalk noise power is -11 dBm.

A Novel Plasmonic Sensor Based on Metal–Insulator–Metal Waveguide With Side-Coupled Hexagonal Cavity

We propose a novel and compact plasmonic sensing structure based on a metal-insulator-metal (MIM) waveguide with a side-coupled hexagonal cavity. The sensing structure has been numerically and theoretically investigated using the finite-difference time-domain (FDTD) method and temporal coupled-mode theory. The numerical simulation results show that the resonance dips of the structure have a high resonant transmission contrast ratio and that the resonance wavelengths have a near-linear relationship with the refractive index of the dielectric material in the cavity. The numerical simulation results obtained from the transmission spectra are used to analyze the sensing characteristic of the structure. The effects of the geometrical parameters on the transmission and sensing characteristics of the structure are analyzed in detail. The sensitivity can be tuned to a value as high as 1562.5 nm per refractive-index unit (RIU) with a high figure of merit of ~38.6 RIU-1 around the resonance wavelength of 1550 nm using the novel structure and by optimizing the structural parameters. In addition, the temperature-sensing characteristic of the structure based on the refractive-index sensor is also discussed in this paper. The proposed structure may potentially be applied in optical networks-on-chip and on-chip nanosensors.

Crosstalk Noise Analysis and Optimization in 5

Crosstalk noise is an intrinsic characteristic of photonic devices used by optical router which is used in optical networks-on-chip. It also adds a new dimension to the design of the optical router based on the photonic devices. We analyzed crosstalk noise at device level and router level. Based on the detailed analysis, we proposed a general analytical model to study the transmission loss, crosstalk noise, optical signal-to-noise ratio (OSNR), and bit error ratio in the 5 × 5 hitless optical router. For the first time, this paper used the crossing angles of 60° or 120° instead of the conventional 90° crossing angle to design the optical router. It is obtained that by using this method OSNR is improved by about 10 dB.

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Abstract. A plasmonic sensor based on a metal–insulator–metal waveguide with a side-coupled nanodisk resonator is proposed and numerically investigated using a finite-difference time-domain method. The numerical simulation results indicate that more than one sharp resonance dip appears in the transmission spectrum in the telecommunication regime, and each resonance wavelength has a linear relationship with the refractive index of the dielectric in the resonator. In addition, the sensing characteristics of the structure and the influence of its structural parameters are analyzed in detail by investigating the transmission spectra. As a refractive-index sensor, its sensitivity can reach as high as 1150 nm per refractive index unit near the resonance wavelength of 1550 nm, and its sensing resolution can reach 10−6 for a wavelength resolution of 0.01 nm. Furthermore, by employing the relationship between the temperature and the refractive index, the temperature-sensing characteristics of the structure are also discussed. Near the resonance wavelength of 1550 nm, the temperature sensitivity can reach 0.45  nm/°C. The sensor has a compact and simple structure and may find many potential and important applications in optical networks-on-chip and on-chip nanosensors.

5 Hitless Silicon-Based Optical Router for Optical Networks-on-Chip (ONoC)

As a new trend, torus-based optical networks-on-chip (ONoCs), which can be considered as an extension of a 2-D network topology based on a mesh topology, can overcome the bandwidth limitation of a conventional electrical networks-on-chip. Although ONoCs have many advantages, crosstalk and insertion loss are the two main causes of the performance degradation and network scalability constraints. When traditional crossing and optical routers are used in the original torus structure, a bit error rate of 10-9 is needed for reliable transmission for a network scale of no more than 5 × 5. To improve the performance of torus-based ONoCs and expand network scalability, an optimum crossing of 60° or 120° is applied in an optical router and network for the first time, instead of the conventional crossing fixed at 90°. Furthermore, a mathematical noise analysis model is presented, and then, used in designing an optical communication systems based on a torus-based optical interconnection network. According to the simulation results, optimized torus-based ONoCs have a better signal-to-noise ratio (SNR) for the path-setup link at a certain network scale compared to a traditional network with fixed crossing angle. For example, when the network scale of a torus-based ONoC is 6 × 6 and the input power is 0 dBm, the SNR of a torus-based ONoC using the optimized structure can reach 23.87 dB, which is 2.21 and 9.27 dB higher than those using crux and optimized crossbar routers, respectively.

Theoretical investigation of a plasmonic sensor based on a metal–insulator–metal waveguide with a side-coupled nanodisk resonator

A plasmonic temperature-sensing structure, based on a metal-insulator-metal (MIM) waveguide with dual side-coupled hexagonal cavities, is proposed and numerically investigated by using the finite-difference time-domain (FDTD) method in this paper. The numerical simulation results show that a resonance dip appears in the transmission spectrum. Moreover, the full width of half maximum (FWHM) of the resonance dip can be narrowed down, and the extinction ratio can reach a maximum value by tuning the coupling distance between the waveguide and two cavities. Based on a linear relationship between the resonance dip and environment temperature, the temperature-sensing characteristics are discussed. The temperature sensitivity is influenced by the side length and the coupling distance. Furthermore, for the first time, two concepts—optical spectrum interference (OSI) and misjudge rate (MR)—are introduced to study the temperature-sensing resolution based on spectral interrogation. This work has some significance in the design of nanoscale optical sensors with high temperature sensitivity and a high sensing resolution.

Performance Optimization and Evaluation for Torus-Based Optical Networks-on-Chip

A novel symmetric image encryption-then-transmission system based on optical chaos using semiconductor lasers is proposed. In this paper, with identical chaotic injection from a master laser, two slave lasers (SL1 and SL2) can output similar chaotic signals served as chaotic carrier to transmit image. Meanwhile, the chaotic signal of SL1 can be used to generate the key of the encryption scheme. After employing the three-dimensional (3D) cat map and logistic chaotic map, the positions of image pixels are shuffled, and the relationship between the cipher-image and the plain-image is confused simultaneously. Therefore, the system can resist the common attacks such as statistical attack, differential attack, and brute force attack. Through numerical simulations, the high quality chaos synchronization between SL1 and SL2 is obtained. When the chaos masking technique is adopted, the image encrypted by the proposed encryption scheme can be successfully transmitted and decrypted in a 10 km single mode fiber channel from SL1 to SL2, which is accompanied by a bit error rate of less than 6.18 × 10-19. Exhaustive tests about security analysis are carried out, demonstrating the valuable feasibility and high security of the image encryption-then-transmission system.

A Plasmonic Temperature-Sensing Structure Based on Dual Laterally Side-Coupled Hexagonal Cavities

A novel plasmonic demultiplexer in metal-insulator-metal (MIM) waveguide crossing with multiple side-coupled hexagonal resonators is proposed and numerically investigated. The operating principle of the structure is analyzed by using the temporal coupled-mode theory. It is found that wavelength demultiplexing can be realized by modulating locations of resonators, which is validated by finite-difference time-domain (FDTD) simulations. In addition, the influences of structural parameters on transmission characteristics are studied by simulations. Simulation results reveal that the demultiplexed wavelength, transmission efficiency, and bandwidth of each channel can be manipulated by adjusting structural parameters of the demultiplexer. The proposed demultiplexer will provide an alternative for the design of highly integrated optical circuits and complex waveguide networks.

Exploiting Optics Chaos for Image Encryption-Then-Transmission

We present a low crosstalk, low losses crossings for silicon-on-insulator waveguides by choosing the optimum crossing angle. The waveguides are broadened using a 3 μm parabolic taper in each arm. It is obtained that by using the crossing angles of 60 deg instead of the conventional 90 deg crossing angle, crosstalk losses are improved by more than 3.7 dB without degrading transmission losses. The transmission behavior of the crossing waveguides are illustrated by numerical simulations through the finite difference time domain method. The proposed crossing structure has a high compactness, a broad bandwidth with almost flat transmission losses, and constant crosstalk losses.