Search

In this paper, we introduce 3D P-Torus, a novel intra-DC architecture, based on the 3-dimensional torus topology, that utilizes wavelength switching at the packet level to achieve improved latency and throughput performance compared to earlier variants of the P-Torus architecture and other wavelength switching intra-DC architectures. By a single-hop communication design between On-Rack Switches, 3D P-Torus achieves great latency and throughput performance, as calculated through detailed simulations. All buffering needs are covered through electronic buffering, avoiding hard to implement and expensive optical buffering. 3D P-Torus can support, with no need for amplification, medium-sized-DCs up to 10k servers, making it an excellent candidate for Edge Data Centers, taking into account its excellent low end-to-end latency. © 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.

Multicore fibers can be used for Radio over Fiber transmission of mmwave signals for phased array antennas in 5G networks. The inter-core skew of these fibers distorts the radiation pattern and has to be measured and compensated. We propose a method to accurately measure the differential delays remotely, after installation, without intervening heavily with the transmitter setup. The properties of the phase response measured at a distant receiver are exploited to acquire the differential delays among the antenna array elements. © 2020, IFIP International Federation for Information Processing.

The scope of this paper is to demonstrate a fully working and compact photonic Physical Unclonable Function (PUF) device capable of operating in real life scenarios as an authentication mechanism and random number generator. For this purpose, an extensive experimental investigation of a Polymer Optical Fiber (POF) and a diffuser as PUF tokens is performed and the most significant properties are evaluated using the proper mathematical tools. Two different software algorithms, the Random Binary Method (RBM) and Singular Value Decomposition (SVD), were tested for optimized key extraction and error correction codes have been incorporated for enhancing key reproducibility. By taking into consideration the limitations and overall performance derived by the experimental evaluation of the system, the designing details towards the implementation of a miniaturized, energy efficient and low-cost device are extensively discussed. The performance of the final device is thoroughly evaluated, demonstrating a long-term stability of 1 week, an operating temperature range of 5 degrees C, an exponentially large pool of unique Challenge-Response Pairs (CRPs), recovery after power failure and capability of generating NIST compliant true random numbers.

In 5G networks, a Radio over Fiber architecture utilizing multicore fibers can be adopted for the transmission of mmwave signals feeding phased array antennas. The mmwave signals undergo phase shifts imposed by optical true time delay networks, to provide squint free beams. Multicore fibers are used to transfer the phase shifted optical signals. However, the inter-core static skew of these fibers, if not compensated, distorts the radiation pattern. We propose an efficient method to compensate the differential delays, without full equalization of the transmission path lengths, reducing the power loss and complexity. Statistical analysis shows that regardless of the skew distribution, the frequency response can be estimated with respect to the rms skew delays. Simulation analysis of the complete Radio over Fiber and RF link validates the method. © 1983-2012 IEEE.

In this work we introduce P-Torus, a wavelength switching architecture for intra-data-center networks that exploits optical-packet-based transport and is based on 2D torus interconnected clusters. P-Torus does not require optical buffers, as all buffering takes place at the end hosts. The proposed architecture combines torus connectivity richness, time-slotted operation, and efficient wavelength routing in order to provide single-hop, contentionless, and low-latency interconnection among all top-of-rack switches. Wavelength switching is performed in wavelength or waveband granularity with the use of fast wavelength-tunable transmitters, in compliance with the optimal solution of the routing and wavelength assignment problem of the generic torus topology. Numerical simulations are carried out to evaluate the latency and throughput performance of the proposed architecture. Results show that P-Torus exhibits low end-to-end latency and high throughput, even under a high load, in uniform and hot-spot traffic scenarios. This work also includes cost and power consumption analyses showing that P-Torus has significant benefits over other contemporary wavelength-based switching architectures. Comparative simulations and cost analysis validate that P-Torus provides a very good trade-off between performance and cost compared to other wavelength-based switching architectures targeting small to medium data centers, up to 10,000 servers. © 2019 OSA.

A tunable high-resolution synthesizer based on optoelectronic phase locked loop is proposed for the generation of microwave and mmWave frequencies. Optical modulation, frequency division, and phase locking processes are deployed to generate a tunable lower frequency exhibiting suppressed phase noise. Moreover, a dense tunable optical comb locked to the widely spaced reference is produced. A suite of microwave and mmWave frequencies in multiple frequency bands emerges from the beating of the generated optical frequency components and optical or electrical filtering may isolate the frequency bands of interest. The phase noise of the synthesized frequencies depends on the optical power of the input reference comb. The experimental evaluation, including Allan deviation and phase noise measurements, prove the high stability performance of the proposed scheme. © 1989-2012 IEEE.

Diffuse optical tomography is an emerging biomedical imaging technique, due to its numerous advantages, such as low cost and non-ionizing radiation. In this work, we have developed a very simple setup, which included a single source - photodiode (SP) pair for scanning a sample of water with diluted Intralipid, simulating a biological tissue. LEDs emitting at 470, 525 and 624 nm, as well as a 650 nm Fabry Perot laser, were used as light sources. Scattered light from the sample was detected by the photodiode placed next to the LED. The SP distance could vary and the phantom could be scanned by moving the SP pair in precise, small and automated steps without any intervention during the measurements. Therefore, we obtained measurements from multiple locations on the sample, with just one SP pair. The presented experimental system verified the feasibility of deploying extremely low cost devices for detection and imaging absorbing objects of 1 cm height, placed inside a scattering medium. Maximum depth detection was 2.5 cm. As expected, the quality of the obtained images was degrading, as the object's depth or the scanning step was increasing. Additionally, we developed Monte Carlo simulations of the setup, which achieved good agreement with the experimental results. We also conducted another set of simulations, studying the depth sensitivity of a single static SP pair considering a scattering medium similar to the experimental phantom with and without object. We observed that the depth sensitivity increases as the source wavelength increases from 450 nm to 650 nm.

In this work, a passive reservoir computing scheme is presented, which relies on the excitation and guiding of transverse modes in a large cross-section photonic waveguide. The optical modes act similar to conventional waveguide-based reservoir nodes, whereas random defects act as the operational equivalent of internode connections. Therefore, the proposed scheme’s number of nodes and connections can scale with the waveguide’s volume, contrary to planar implementations. The principle of operation, alongside the role of mode defects to performance, is validated through a numerical model, whereas the classification of time-dependent, 2D analog/digital image streams is used as an application-relevant benchmark test. © 2019 Optical Society of America.

In an environment where cyber attacks are increasing, both in frequency and complexity, novel ways to shield data, users, and procedures have to be envisioned. Physical unclonable functions (PUFs) are the physical equivalent of one-way mathematical transformations with the exception that their inherent physical complexity renders them resilient to cloning. One interesting deployment scenario includes PUFs as random key generators. The deterministic nature of their operation alleviates the necessity to store the keys in non-volatile means. Along the same lines, blockchain is inherently resistant to modification of the data once stored while their overall security depends on the quality and secrecy of users' keys. Here, the authors propose a novel optical PUF implementation that can be combined with private blockchain modalities in order to cyber-harden Internet of things ecosystems. PUF-related experimental results are presented, alongside implementation scenarios. © 2018 The Institution of Engineering and Technology.

International audience

International audience

Data centers are continuously growing in scale and can contain more than one million servers spreading across thousands of racks; requiring a large-scale switching network to provide broadband and reconfigurable interconnections of low latency. Traditional data center network architectures, through the use of electrical packet switches in a multi-tier topology, has fundamental weaknesses such as oversubscription and cabling complexity. Wireless intra-data center interconnection solutions have been proposed to deal with the cabling problem and can simultaneously address the over-provisioning problem by offering efficient topology re-configurability. In this work we introduce a novel free space optical interconnect solution for intra-data center networks that utilizes 2D optical beam steering for the transmitter, and high bandwidth wide-area photodiode arrays for the receiver. This new breed of free space optical interconnects can be developed on a photonic integrated circuit; offering ns switching at sub-μW consumption. The proposed interconnects together with a networking architecture that is suitable for utilizing those devices could support next generation intra-data center networks, fulfilling the requirements of seamless operation, high connectivity, and agility in terms of the reconfiguration time. © 2018 by the authors.

Physical unclonable functions are the physical equivalent of one-way mathematical transformations that, upon external excitation, can generate irreversible responses. Exceeding their mathematical counterparts, their inherent physical complexity renders them resilient to cloning and reverse engineering. When these features are combined with their time-invariant and deterministic operation, the necessity to store the responses (keys) in non-volatile means can be alleviated. This pivotal feature, makes them critical components for a wide range of cryptographic-authentication applications, where sensitive data storage is restricted. In this work, a physical unclonable function based on a single optical waveguide is experimentally and numerically validated. The system's responses consist of speckle-like images that stem from mode-mixing and scattering events of multiple guided transverse modes. The proposed configuration enables the system's response to be simultaneously governed by multiple physical scrambling mechanisms, thus offering a radical performance enhancement in terms of physical unclonability compared to conventional optical implementations. Additional features like physical re-configurability, render our scheme suitable for demanding authentication applications. © 2018 The Author(s).

In this work, a photonic physical unclonable function module, based on an optical waveguide, is demonstrated. The physical scrambling mechanism is based on the random and complex coherent interference of high order optical transverse modes. The proposed scheme allows the generation of random bit- strings, through a simple wavelength tuning of the laser source, that are suitable for a variety of cryptographic applications. The experimental data are evaluated in terms of unpredictability, employing typical information theory benchmark tests and the NIST statistical suit. © 2018, The Author(s).

National audience