Optical Signal Generation Research Articles

A March to Shape Optical Artificial Olfactory System toward Ultrasensitive Detection of Improvised Explosives

Improvised explosives (IEs) have been frequently used in explosion‐based terrorist attacks, and have aroused widespread concerns from governments to academic societies. Due to the fact that IEs mostly exist as solids, there is a pressing demand for sensors to adapt to acquire the information from the solid state. Chemical sensors usually comprise with probes designed based on the chemical properties of the analytes, and generate signals through specific chemical interactions, which would not be affected by the state of the target substance. Colorimetry and fluorescence, known for their intuitionistic (recognizable by human eyes), portable (independent of large‐scale analytical equipment), highly specific, sensitive, and environmental interference‐free characteristics, are commonly adopted optical chemical detection methods in materials analysis and environmental monitoring. Based on this, the exploration of optical artificial olfactory system, which mimics the working principle of natural olfactory system and acquires sensing signal by optical methods, has emerged to be a promising tool for IEs detection. Here, the basic working principle and the necessary components of optical artificial olfactory system are recommended, including probe molecule, array composition, pattern recognition and device construction. The potential development direction employing molecular recognition of IEs, generation, and acquisition methodology of optical signals are also prospected.

Optical Chemosensors for Cations Based on 1,8-Naphthalimide Derivatives

This review presents the examples of fluorescent sensors for metal cations based on a 1,8-naphthalimide optical platform and covers the main advances in this field for the last decade. The mechanisms of the generation of an optical signal are discussed in detail. Special attention is given to the authors' own works.

Dual Sensitivity─Potentiometric and Fluorimetric─Ion-Selective Membranes.

Classical application of ion-selective membranes is limited to either electrochemical or optical experiments. Herein, the proposed ion-selective membrane system can be used in both modes; each of them offering competitive analytical parameters: high selectivity and linear dependence of the signal on logarithm of analyte concentration, high potential stability in potentiometric mode, or applicability for alkaline solutions in optical mode. Incorporation of analyte ions into the membrane results in potentiometric signals, as in a classical system. However, due to the presence of lipophilic positively charged ions, polymer backbones, full saturation of the membrane is prevented even for long contact time with solution. The presence of both positively charged and neutral forms of conducting polymers in the membrane results in high stability of potential readings in time. Optical signal generation is based on polythiophene particulates dispersed within the ion-selective membrane as the optical transducer. An increase of emission is observed with an increase of analyte contents in the sample.

Optical chaos generated in semiconductor lasers with intensity-modulated optical injection:a numerical study

We numerically report on an optical chaos signal generation scheme based on a semiconductor laser subject to intensity-modulated (IM) optical injection. In this scheme, the characteristics of the chaos signal obtained by destabilizing period-one nonlinear dynamics are numerically investigated. With the aid of bifurcation diagrams and the 0-1 tests for chaos, the chaotic dynamics excited by continuous-wave and IM optical injection are located, and the effects of injection and modulation parameters on chaotic regions are illustrated. Moreover, effective bandwidths and auto-correlation characteristics of chaos signals from the IM optical injection system are systematically investigated. The results show that although chaotic signals under the IM optical injection scenario have a limitation in unambiguous range detection in most parameter regions, wideband chaotic dynamics in large injection and modulation parameter regions can be easily achieved. This study paves the way for potential applications requiring no time-delay signature and broad bandwidth chaos, such as high-speed chaos communications and random bit generation.

Stern and Diffuse Layer Interactions during Ionic Strength Cycling

Second harmonic generation amplitude and phase measurements are acquired in real time from fused silica:water interfaces that are subjected to ionic strength transitions conducted at pH 5.8. In conjunction with atomistic modeling, we identify correlations between structure in the Stern layer, encoded in the total second-order nonlinear susceptibility, chi(2)tot, and in the diffuse layer, encoded in the product of chi(2)tot and the total interfacial potential, phi(0)tot. chi(2)tot:phi(0)tot correlation plots indicate that the dynamics in the Stern and diffuse layers are decoupled from one another under some conditions (large change in ionic strength), while they change in lockstep under others (smaller change in ionic strength) as the ionic strength in the aqueous bulk solution varies. The quantitative structural and electrostatic information obtained also informs on the molecular origin of hysteresis in ionic strength cycling over fused silica. Atomistic simulations suggest a prominent role of contact ion pairs (as opposed to solvent-separated ion pairs) in the Stern layer. Those simulations also indicate that net water alignment is limited to the first 2 nm from the interface, even at 0 M ionic strength, highlighting water's polarization as an important contributor to nonlinear optical signal generation.

Indoor and Outdoor Surface Measurement of 3D Objects under Different Background Illuminations and Wind Conditions Using Laser-Beam-Based Sinusoidal Fringe Projections

In this study, both theoretical analysis and experimental validation are carried out for 3D surface measurement under different indoor/outdoor environmental conditions via combining the projected laser-beam-based sinusoidal optical signal, the optical filtering technique, and the single-shot approach based on Fourier transform profilometry. The designed optical signal generator used in this work is capable of ensuring that the projected fringe pattern is monochromatic, higher-contrast, time-invariant, and truly sinusoidal. The proposed and developed optical setup of 3D surface measurement is portable and is used for in-situ experiments of 3D surface measurements that have been carried out under different sunlight illuminations. The experimental results indicate that accurate reconstructions of measured objects with even or varying surface reflectivity can be obtained under windy conditions and strong environmental illuminations such as the background illuminance of 5600–35,000 Lux. The generated fringe-pattern signal is not sensitive to vibrations from environmental influences including the effects of the wind, which has overcome the outdoor-measurement restrictions of the traditional interferometric system and the profilometry approaches based on phase-shifting methods.

A comprehensive review of Millimeter wave based radio over fiber for 5G front haul transmissions

Objectives: To find out how fiber distribution system could be utilized for 5G based futuristic higher capacity and lower latency front haul transmission system. Findings: Integrating the transmission of Millimeter wave (Mm wave) signals over the Radio over Fiber (RoF) system i.e. Mm-RoF can be seen as a promising candidate that would satisfy the requirement imposed by 5G wireless system. Further, optical generation of Mm wave signals is a major concern that needs to be taken care of and some appropriate hybrid photonic generation methods should be employed for Mm wave signal distribution over the RoF system that incur lower installation cost and higher transmission performance. Applications: This will enrich the researchers with valuable content on single platform and motivate them to undertake the research work towards the advancement in the photonic generation of Mm wave signals over the RoF network for 5G applications with reduced system cost and complexity. Keywords: Radio over Fiber; Mm-wave technology; 5G networks; optical signal generation; Mm wave based RoF etc

One-step-immunoassay of procalcitonin enables rapid and accurate diagnosis of bacterial infection.

Procalcitonin (PCT) (i.e. a precursor of calcitonin) attracts much attention as a reliable biomarker of bacterial infections because its concentration increases rapidly in the blood when bacterial infections occur in the body. Sepsis may occur due to indiscriminate and vigorous proliferation of infectious bacteria, and accordingly early diagnosis and treatment of bacterial infection are of crucial importance. However, current diagnostic methods for sepsis suffer from long assay time, multiple and complex assay steps, inaccuracy, and requirement of analytical equipments. The goal of this study is to develop an advanced one-step-immunoassay that enables quick and accurate diagnosis of sepsis through measuring the PCT concentration in patient sera, which is based on self-enhancement of optical detection signals from large gold particles (i.e. clusters of gold nanoparticles) that are formed on the agglomerates of PCT-bound 3-dimensional (3D) probes. The 3D probe is constructed through attaching polyclonal anti-PCT antibodies (IgGs) to the surface of a modified hepatitis B virus (HBV) capsid, where both tandem repeats of the B domain of Staphylococcal protein A (SPAB) and the hexa-histidine tag are inserted into each HBV core protein (i.e. subunit of HBV capsid). That is, anti-PCT IgGs are attached via strong interaction between the Fc region and surface-exposed SPAB. Furthermore, hook effect-free and PCT concentration-dependent optical signals were consistently generated by adding both bovine serum albumin (BSA) and nickel ions to patient sera and also by optimally adjusting the 3D probe concentration. Compared to conventional chemiluminescent microparticle immunoassay (CMIA) showing poor linearity of detection signals, this novel immunoassay accurately detected PCT with good linearity between PCT concentrations and optical signals in a wide range of PCT concentrations (0.05–200 ng mL−1) and also showed a sufficiently low limit of detection, resulting in 100% sensitivity and 100% specificity when tested with 30 sepsis patients and 30 healthy individuals.

A Robust Sparse RLS-Volterra Nonlinear Equalizer Using ℓ₀-Regularization for 4 × 150 Gbit/s IMDD-Based Optical Interconnect

Volterra equalizer (VE) is a well-known and effective algorithm to deal with the linear and nonlinear distortions in optical interconnect, but the high computational complexity hinders its practical application. Generally, sparse VEs based on ℓ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> - or ℓ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> -regularization are good ways to reduce the complexity by discarding some inessential taps. However, a tap threshold needs to be chosen in these sparse VEs like the threshold-based pruned retraining VE (TR-VE) to decide the discarded taps. And this tap threshold should be adjusted fine to balance the reduced complexity and equalization performance, especially when the testing environments alter. Thus, the reduced complexity in these sparse VEs may fluctuate. To address this issue, a robust and stable complexity reduced sparse VE using ℓ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> -regularization (ℓ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> -SR-VE) is proposed in this paper. The recursive least square (RLS) algorithm is used to replace the least mean square algorithm for the faster convergence speed and better equalization performance. The complexity of this equalizer depends on its parameters but not the tap threshold. Once the equalizer parameters are determined, the complexity would not change with the system characteristics, contributing to higher practicability. In our experiment, a 150 Gbit/s PAM8 signal transmission system based on intensity modulation and direct detection (IMDD) is achieved, and a dual-drive Mach-Zehnder modulator for optical single-sideband signal generation is used to mitigate the power fading effect. The experimental results show that with the help of ℓ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> -SR-VE, the reduced complexity percentage is stable at 66.18% compared with the RLS-based VE, even after 75 km standard single-mode fiber (SSMF) transmission. By using this equalizer, 4×150 Gbit/s PAM8 signals have also been successfully transmitted over 30 km SSMF at C-band. The reduced complexity variation of ℓ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> -TR-VE is >20%, but the reduced complexity of the proposed ℓ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> -SR-VE is stable at 60% even after 30 km SSMF for all four lanes.

Generation of optical signals carrying OAM based on vortex fiber-optic periodic structures

In this article, author considers the process of generation of fiber modes carrying orbital angular momentum (vortex modes) using chiral fiber Bragg gratings; in this context, the formation of vortex modes is carried out by converting thefundamental mode into higher order modes. Within the framework of the article, a generalized mathematical model of chiral fiber Bragg gratings is presented, which includes an arbitrary function of apodization and chirping, which makes it possible to calculate gratings that form vortex modes of a given order for the required frequency range with the required reflection coefficient. In addition, a matrix method for describing chiral fiber Bragg gratings is proposed, based on the mathematical apparatus of the coupled modes theory and scattering matrices. This matrix approach is convenient for describing complex and / or cascaded gratings. In addition, in this work, simulation of the considered fiber structures is carried out.

(Invited) The Contribution of Thin Film Technologies to the Future Challenges of a Connected Society

This paper highlights the future challenges related to the exponential development of connected objects and the Internet of Things. These challenges concern the integration of components, circuits and systems, the density of elementary components, but also the heterogeneous assembly, the data flow in communications and the energy consumption of the whole connected system. Indeed, current technologies and the amount of data transmitted currently lead to an exponential growth in energy consumption at the global level, a growth that will no longer be realistic and acceptable from 2030 onwards. To counteract this, the entire chain of integrated functions that are physically realized by microelectronic components, circuits and systems needs to be revisited. The main challenges will therefore focus on reducing the consumption of electronic functions including sensors and actuators, signal conversion and processing devices, energy collection and storage devices, display panels and short- and long-distance communications systems, and power electronics as well. Among these points, it should be noted that the number of sensors is increasing significantly, with predictions indicating that the number of sensors in the world is expected to reach 10 trillion by 2030, which corresponds to about a thousand sensors per inhabitant. Moreover, a strategy will have to be adapted not to increase the flow of data transmitted over long distances to data centers and cloud storage (or equivalent), but rather to prefer the use of short-range communications, which are much less energy-intensive.This evolution involves new technological approaches including very highly integrated components and circuits (ULSI or Ultra Large Scale Integration) but also thin film technologies based on inorganic and organic materials. These technologies are becoming a priority for the development of integrated sensors, energy production and storage systems and for the realization of transducers such as electrical generation of optical signals or contact-controlled flat panel displays. Three-dimensional heterogeneous structures combining the stacking of highly integrated devices with the superposition of thin film devices are also promising for data storage, which is becoming one of the major elements of databases and data centers.Depending on the desired properties, the solutions are more based on the modification of the materials constituting the basic electronic components in order to minimize the currents in the off-state but also the on-state, on the architectures of the circuits which must limit the consumption at stand-by, on the stacking of the layers constituting the devices and finally on the heterogeneous assembly involving several technologies. This will also require adapting the skills and know-how of technicians, engineers, doctors and researchers in order to overcome the technological challenges.This paper will thus successively focus on a general presentation of the challenges related to the development of connected objects and the Internet of Things, which involve all the main functions of electronics, which have consequences on all societal domains since the vast majority of applications in rapid development use electronic components and systems. Particular attention will be paid to the energy consumption of components and circuits that induce an exponential consumption of connected objects and the Internet. The next part will focus on the different approaches envisaged and more particularly on thin-film devices. In order to complete the picture, the last part will focus on the human needs in skills and know-how by giving as an example the strategy of the French microelectronics training network carried out over the last ten years. The final objective is to take up the technological and human challenges within the framework of the French electronics sector, set up in 2019 by the French government, which aims at making a significant contribution at the international level in the development of the digital society involving the Internet of Things, artificial intelligence and industry 4.0.

Turbulence mitigation in a 28 GHz radio‐over‐free‐space optics link using an integrated Mach–Zehnder interferometer and a diversity combining receiver

The authors propose an integrated Mach–Zehnder interferometer and diversity combining receiver to mitigate the atmospheric turbulence-induced fading in a millimetre-wave (mmW) radio-over-free-space optics (RoFSO) link. They use a carrier frequency of 28 GHz as recommended for the fifth-generation wireless access networks and consider two optical mmW signal generation schemes, namely double-sideband (DSB) and single-sideband (SSB). In direct detection (DD)-based RoFSO, the link performance is limited by atmospheric turbulence. They show that the proposed Rx can overcome this detrimental effect, which is verified by investigation of a 10 Gb/s 16-quadrature amplitude modulation orthogonal frequency-division-multiplexing signal at 28 GHz over a 1 km free-space optics link under weak and strong turbulence regimes. For the DSB scenario, the proposed Rx offers improved error vector magnitudes of about 0.8 and 5.7%, and modulation error ratios of 1.3 and 4.9 dB under weak and strong turbulence regimes, respectively, compared with the DD receiver (DD Rx). For the SSB scenario under weak turbulence, the proposed Rx achieves a 4 dB improvement in the receiver sensitivity and four orders of magnitude enhancement in the bit error rate over the DD Rx. The proposed Rx can be integrated on a single chip for further cost reduction.

All-Fiber Hyperparametric Generation Based on a Monolithic Fiber Fabry–Pérot Microresonator

Hyperparametric oscillation is essential for coherent optical signal generation in a broad wavelength range. Integration in a compact system, such a broadband light source, is of special interest for practical applications requiring field-deployable spectroscopy devices. Here we demonstrate an all-fiber hyperparametric oscillation source based on four-wave mixing in a high-Q fiber Fabry–Pérot (FFP) microresonator. Assisted by the Raman effect, the generated optical signal spans over 400 nm with fine line-to-line spacing of 667 MHz. The compatibility of this FFP microresonator enables a robust and reliable all-fiber system through a splicing technique and fiber connectors. Such a plug-and-play platform is convenient and efficient for broad applications in optical communications and spectroscopy.

Influence of Different Structure and Specification Parameters on the Propagation Characteristics of Optical Signals Generated by GIL Partial Discharge

Partial discharge (PD) leads to the generation of electrical, acoustic, optical, and thermal signals. The propagation characteristics of optical signals in gas insulated metal-enclosed transmission lines (GIL) are the basis of optical detection research. This paper simulates the propagation of PD optical signals in GIL through modeling GIL with different structures and specification parameters. By analyzing the optical parameters on the probe surface and the detection points when the PD source position is different, the influence of the difference in specifications caused by the voltage level on the propagation of the GIL PD optical signal is studied. The results show that the GIL cavity structure will affect the faculae distribution and the relative irradiance (RI) of the detection surface; the PD source position has a huge impact on the faculae distribution on the detection surface, but has little influence on the RI; as the voltage rises, the faculae distribution on the detection surface becomes more obvious, and the mean of RI decreases. The above results have the reference value for the manufacture of GIL equipment and the research of PD optical detection. When the specular reflection coefficient of surface material is smaller and the diffuse reflection coefficient is larger, the outline of the light spot is clearer, the proportion of brighter parts is larger, and the maximum value of the RI is larger.

Bursting oscillations in Colpitts oscillator and application in optoelectronics for the generation of complex optical signals

We are exploring an optoelectronic oscillator featuring a Colpitts oscillator in its electrical path. The Colpitts oscillator generates high frequency electrical signals and exhibits dynamical behaviors such as periodic and bursting oscillations which can be easily monitored using a potentiometer. Inserting the Colpitts oscillator in the optoelectronic oscillator, we put forward the interaction between optical nonlinearity and electronic nonlinearity to obtain also complex dynamical behaviors. The temporal dynamics of the system with and without delayed feedback is investigated experimentally. It is shown that a wide variety of periodic and chaotic states can be excited and that there is an amplification of the signal frequencies. In particular, bursting, chaotic bursting and chaotic pulse-package oscillations with slow-fast temporal dynamics are experimentally observed in the system.

Spectral and temporal optical signal generation using randomly distributed quantum dots

Quantum dots (QDs) have a great potential for realizing information processing because of their signal-modulation capability based on energy transfer. We present a method for generating diverse temporal and spectral signals based on the energy transfer between multiple QDs. The method uses randomly distributed QDs, so it is not necessary to precisely arrange a QD network. With multiple energy transfers between QDs, a variety of signals within the QD network can be generated by optical inputs. Experimental results revealed that fluorescence decays of dense QDs were faster when the density of QDs or the irradiation intensity decreased. Furthermore, depending on the positions, stacked QDs showed different spectral responses. The randomly distributed QDs can generate diverse signals, which is essential for signal processing to handle temporal information.

Differential drive I/Q modulator based on silicon photonic electro-absorption modulators

We demonstrate up to 100 Gbaud quadrature-amplitude modulated (QAM) signal generation with monolithic silicon in-phase quadrature (I/Q)-modulator based on silicon-germanium (SiGe) electro-absorption modulators (EAM). The modulator is in a differentially driven Mach–Zehnder (MZ) interferometric configuration similar to the conventional MZ modulator (MZM) based (I/Q) modulators. In particular, single-polarization quadrature phase-shift keying (SP-QPSK) signaling at symbol rates of 100 Gbaud with BERs below the hard-decision forward error correction (FEC) limit is shown. SP-QPSK optical signal generation and transmission over 80 km single-mode fiber (SMF) are demonstrated at symbol rates of 50 Gbaud with BER of less than $\mathbf {10^{-5}}$ . The effect of the frequency roll-off used for Nyquist pulse shaping with raised cosine frequency response is studied for SP-QPSK 50 Gbaud signals. Furthermore, 16QAM signals at symbol rates of 50 Gbaud are generated.

Optical vector analysis with attometer resolution, 90-dB dynamic range and THz bandwidth

Optical vector analysis (OVA) capable of achieving magnitude and phase responses is essential for the fabrication and application of emerging optical devices. Conventional OVA often has to make compromises among resolution, dynamic range, and bandwidth. Here we show an original method to meet the measurement requirements for ultra-wide bandwidth, ultra-high resolution, and ultra-large dynamic range simultaneously, based on an asymmetric optical probe signal generator (ASG) and receiver (ASR). The ASG and ASR remove the measurement errors introduced by the modulation nonlinearity and enable an ultra-large dynamic range. Thanks to the wavelength-independence of the ASG and ASR, the measurement range can increase by 2 N times by applying an N-tone optical frequency comb without complicated operation. In an experiment, OVA with a resolution of 334 Hz (2.67 attometer in the 1550-nm band), a dynamic range of > 90 dB and a measurement range of 1.075 THz is demonstrated.

8 phase-shift-keying optical millimeter-wave signal generation by electro-optical phase modulator-based photonic frequency quintupling

We have proposed an 8 phase-shift-keying (PSK) optical millimeter-wave (MMW) signal generation scheme with frequency quintupling enabled by an electro-optical phase modulator (PM) and a wavelength selective switch. In this scheme, the radio frequency (RF) carrier with 8PSK signal is modulated on the lightwave via the PM with simple precoding but constant Euclidean distance, and is recovered to the original 8PSK signal with the frequency-quintupling RF carrier based on the phase periodicity of an 8PSK signal. By optimizing the voltage amplitude of the 8PSK RF driving signal, the generated frequency-quintupled 8PSK MMW signal is maximized at a given laser launch power. A radio over fiber simulation link is built to demonstrate the theoretical analysis. The simulated constellations and bit-error-rate curves show that the frequency-quintupling 8PSK MMW signal has good transmission performance. The simulation results agree well with our theoretical prediction.

All optical Millimeter-wave signal generation and transmission for radio over fiber (RoF) link

&lt;span&gt;Fiber-based wireless system has become a promising solution as a cost- effective communication and it offers high capacity network with millimeter- wave (mm-wave) signal transmission. The system significantly offers superior possible bandwidths for both fiber and free-space applications. Hence, with the increased capacity as well as wireless mobile network applications particularly at mm-wave signal, radio over fiber (RoF) technology is the utmost option. Nevertheless, when high frequency signal transmission is involved, power fading or dispersion effect limits the performance of RoF link. Therefore, this work proposed a RoF system by integrating remote optical local oscillator (LO) with frequency up-conversion at the base station (BS). All optical mm-wave signals are generated and transmitted for the RoF link. The effects of the changes of fiber loop length, optical power of the continuous wave (CW) optical laser carrier and responsivity value of the p-i-n photodiode (PD) mainly at 40 GHz are investigated and the power fading effects are discussed.&lt;/span&gt;