Insertion Loss Change Research Articles

Broadband multimode 3 dB optical power splitter using tapered couplers.

A design of a 1 × 2 multimode 3 dB optical power splitter using tapered couplers is proposed and investigated in this paper. As an example, a 1 × 2 splitter processing five-lowest order transverse-electric-polarized modes is designed and optimized by utilizing finite difference time domain method and particle swarm optimization algorithm. To verify the feasibility of this novel design, the optimized device is fabricated on a silicon-on-insulator platform. The coupling lengths of tapered couplers are respectively 6.5 µm, 6.0 µm, 3.5 µm, 5.0 µm, 5.0 µm, 7.5 µm, 6.0 µm, 5.0 µm, and 8.0 µm. Measurement results reveal that, for the fabricated splitter, the power uniformity varies from 0.041 to 0.88 dB, the crosstalk ranges from -23.96 to -14.12 dB, and the insertion loss changes from 0.089 to 1.50 dB within a bandwidth from 1520 to 1600 nm.

Energy transfer and power consumption analysis of coaxial ring TSV

The purpose of this paper is to design and simulate a coaxial ring TSV, and to analyze the behavior of energy transmission and power consumption of the structure during the feeding process. By controlling the structure parameters suitable for low-power, high-performance feeding transmission, the power is maximized from the feeder to the receiver, thus achieving low power consumption. The designed coaxial ring TSV will use the finite element analysis method to simulate and verify the change of insertion loss of silicon through hole at different frequencies. At the same time, the mathematical equivalent models of internal resistance, capacitance, conductivity and power of coaxial ring TSV are extracted. The simulation results show that compared with the cylindrical TSV structure, the insertion loss of this structure is smaller, indicating that the energy loss is smaller. It has research significance for energy saving of packaging system and complete transmission of electrical signal in integrated circuit.

A 5-Gb/s Adaptive Continuous Time Linear Equalizer Using Ferroelectric Capacitor

This article presents a 5-Gb/s continuous-time linear equalizer (CTLE) for serial link interface where adaptive nature is achieved using a ferroelectric capacitor. This barium strontium titanate (BST)-based STPTIC-15G2 capacitor model from STMicroelectronics provides a smooth 5:1 tuning range for a voltage range of 0&#x2013;18 V and eliminates the use of blocking capacitor required in case of varactor diode. The tunability of the high-pass filter response of the proposed CTLE provides the flexibility to meet the allocated loss budget of any serial link more precisely than a design with a discrete value capacitor. Also, its design methodology is much simpler than conventional MOSFET-based CTLE. Moreover, it avoids the use of complex algorithms seen in the case of digital equalization. For validation, the design is implemented on an FR4 board. While studying the data rate tolerance and channel tolerance of the printed prototype, the measured results closely match the simulation results. The compensation level of the equalizer is verified for an FR4 channel by varying its length from <inline-formula> <tex-math notation="LaTeX">$7^{\prime \prime }$ </tex-math></inline-formula> to <inline-formula> <tex-math notation="LaTeX">$28^{\prime \prime }$ </tex-math></inline-formula> which is equivalent to a change in insertion loss from 1.3 to 5.2 dB at 2.5 GHz, which is the Nyquist frequency for a 5-Gb/s signal. Also, for a <inline-formula> <tex-math notation="LaTeX">$28^{\prime \prime }$ </tex-math></inline-formula> FR4 channel, a channel loss requirement of 8&#x2013;9.5 dB is achievable by simply varying the applied bias to the ferroelectric capacitor from 0 to 10 V.

A Surface Acoustic Wave Sensor with a Microfluidic Channel for Detecting C-Reactive Protein

A surface acoustic wave (SAW) sensor with a microfluidic channel was studied to detect C-reactive protein (CRP). A piezoelectric lithium niobate substrate was used to examine the frequency response of the microfluidic SAW sensor. The amplitude (insertion loss) changes in the microfluidic SAW sensor were measured from the interaction of CRP/anti-CRP owing to mass variation. The fabricated microfluidic SAW sensor exhibited a detection limit of 4 ng/mL CRP concentration. A wide CRP concentration range (10 ng/mL to 0.1 mg/mL) can be detected by this sensor, which is higher than the existing CRP detection methods. A good linear relationship between the amplitude peak shift and CRP concentrations from 10 ng/mL to 0.1 mg/mL was obtained. The amplitude peak shifts in the sensor can be useful for estimating CRP concentration. This can be used as a biosensor to diagnose the risk of cardiovascular disease.

Time-frequency optical filtering: efficiency vs. temporal-mode discrimination in incoherent and coherent implementations.

Time-frequency (TF) filtering of analog signals has played a crucial role in the development of radio-frequency communications and is currently being recognized as an essential capability for communications, both classical and quantum, in the optical frequency domain. How best to design optical time-frequency (TF) filters to pass a targeted temporal mode (TM), and to reject background (noise) photons in the TF detection window? The solution for 'coherent' TF filtering is known-the quantum pulse gate-whereas the conventional, more common method is implemented by a sequence of incoherent spectral filtering and temporal gating operations. To compare these two methods, we derive a general formalism for two-stage incoherent time-frequency filtering, finding expressions for signal pulse transmission efficiency, and for the ability to discriminate TMs, which allows the blocking of unwanted background light. We derive the tradeoff between efficiency and TM discrimination ability, and find a remarkably concise relation between these two quantities and the time-bandwidth product of the combined filters. We apply the formalism to two examples-rectangular filters or Gaussian filters-both of which have known orthogonal-function decompositions. The formalism can be applied to any state of light occupying the input temporal mode, e.g., 'classical' coherent-state signals or pulsed single-photon states of light. In contrast to the radio-frequency domain, where coherent detection is standard and one can use coherent matched filtering to reject noise, in the optical domain direct detection is optimal in a number of scenarios where the signal flux is extremely small. Our analysis shows how the insertion loss and SNR change when one uses incoherent optical filters to reject background noise, followed by direct detection, e.g. photon counting. We point out implications in classical and quantum optical communications. As an example, we study quantum key distribution, wherein strong rejection of background noise is necessary to maintain a high quality of entanglement, while high signal transmission is needed to ensure a useful key generation rate.

Research on drop reliability of PLC optical splitters by online test

Mechanical impact may cause structural damage or optical performance failure of devices, but devices in actual use still need to be able to work stably and normally when they are subjected to mechanical impact such as drop impact. Through online drop tests, it was found that the planar lightwave circuit (PLC) optical splitter did not fail during horizontal drops and lateral drops (the maximum insertion loss change was 0.243 dB in 40 horizontal drops and 0.134 dB in 40 lateral drops). During vertical drop impact, obvious optical performance failure and structural damage occurred. The structural damage caused by multiple vertical drop impact was the main reason for the failure of PLC optical splitters.

A Novel Surface Acoustic Wave Biosensor for Real-Time Monitoring of Cell Contractile Properties

Introduction Contraction of cardiomyocytes is a vital property of the heart and its assessment is significant for drug discovery. At present, many researches focus on the electrophysiology detection through microelectrode arrays (MEAs) [1-2]. However, mechanical properties of cardiomyocytes is also critical for many biological processes including cell growth, motility, division, differentiation, and tissue homeostasis [3]. Currently, the atomic force microscope (AFM) has been used to measure the contractile properties of cardiomyocytes. However, the AFM is only suitable for single cells and can only measure one cell at one time. Therefore, it’s necessary to develop a detection system that can monitor the contractile properties of cardiomyocyte in a real-time and dynamic way.Recently, the surface acoustic wave (SAW) sensor has been greatly developed as a well-performed mass sensing device for label-free immunoassay due to its attractive advantages, including real-time monitoring and simplicity of use [4]. In particular, the guided shear horizontal (SH) SAW sensor, which is also known as the Love Wave sensor, has shown its advantages in biosensor applications due to its high sensitivity and stability in the liquid phase [5]. Hence, SAW is a device capable of monitoring viscoelastic properties of a population of cells, which correlates with stiffness, in a non-invasive, label free and continuous manner up to several days to weeks.In this study, a Love Wave sensor was used to study the contractile properties of HL-1 cardiomyocytes, where changes in insertion loss and phase position of the sensor can reflect the mechanical changes (contraction and viscoelasticity). Different compounds were added to test the different effects on the contractile properties of HL-1 cardiomyocytes, and the signals were analyzed by principal component analysis (PCA). Method In this study, the Love Wave sensor is constructed based on a piezoelectric quartz substrate. Interdigitated transducers (IDTs) with Ti/Au (20/200 nm) are deposited to generate pure shear horizontal acoustic waves. The input and output IDTs electrodes consist of 50 split-finger pairs with a wavelength λ=28 μm, which determines the center frequency of the sensor to be about 160 MHz [4]. The distance between IDTs centers is 200λ and the acoustic aperture is 75λ. Afterwards, the IDTs patterned substrate is guided with a 3 μm SiO2 film deposited by plasma enhanced chemical vapor deposition (PECVD). Au layer (200 nm) is deposited on top of guiding layer to improve the cell attachment on the sensor surface.A polydimethylsiloxane (PDMS) chip was designed and used as the cell culturing chamber. The height and volume of this cavity are about 10 mm and 150 μL, respectively. A portable and miniaturized multi-channel Love Wave sensor detection system was developed to detect both the insertion loss and phase signals of sensors. And then, HL-1 cardiomyocytes with 10,000 cells were seeded on the sensor chip. To test the function of the detection system, isoprenaline (ISO) and verapamil (VRP) with different concentrations were used to induce changes in the contractile properties of HL-1 cells. Results and Conclusions VRP is a calcium channel antagonist that blocks the L-type calcium channel and prevents calcium influx into the cell, thereby decreasing the cardiomyocyte contraction force. With the addition of VRP solutions, the insertion loss of Love Wave sensors increased, and the magnitudes of insertion loss increased with the increase of VRP concentration. Our results indicated that the stiffness of living HL-1 cells decreased after VRP administration. Moreover, the higher the VRP concentration is, the softer the HL-1 cells are within the dosage range tested. In contrast to VRP, ISO is positive inotropic drug. After ISO treatment, HL-1 cells wrinkled due to the traction forces. Therefore, the higher the ISO concentration, the larger the traction force and the tighter is the contact of the cells with the sensor substrate, and the stiffer the cells. Moreover, the responses of SAW sensor treated by VRP and ISO could be distinguished by PCA.As far as we know, this is the first report that study the contractile properties of a cardiomyocytes cell line based on a SAW biosensor. The affection on cardiac contractility of different compounds can be monitored by recording the changes in insertion loss and phase position of the SAW sensor. Our results demonstrated that the SAW sensor is a potential new tool for in vitro cardiac contractility evaluation and has promising applications in drug discovery, safety screening and many other fields.

Online Research on Reliability of Thermal-Vibration Coupling for PLC Optical Splitters

The working environment of Planar Lightwave Circuit (PLC) optical splitter is complex and diverse. In addition to withstanding the test of environmental temperature changes, the device may also be affected by mechanical shock such as vibration. Through the thermal-vibration coupling online test, it was found that the insertion loss of the PLC optical splitter changes significantly when the vibration test is performed under high temperature and low temperature environment (the maximum insertion loss change was 4.491dB at 75 °C, and 3.941dB at -40°C). In the same temperature environment, the optical performance of the device during the lateral test and the vertical test was more affected by vibration than in the horizontal test. The study of reliability under combined vibration and temperature fields is helpful to understand and improve the ability of devices to work normally in complex environments.

Insertion loss analysis of slender beams with periodic curvatures using quaternion-based parametrization, FE method and wave propagation approach

The use of repeating cells in general wave theory is a well-known method for obtaining filter-like characteristics. This work targets the effects of periodic structures and their filtering behaviour on the waves propagating through structural paths. To this intent, a finite element (FE) procedure was developed specially to use the wave propagation approach, called NuSim, which uses semi-infinite elements as boundary conditions and calculates power flow coefficients through displacement responses. This particular combination of actions turns this algorithm suitable for analyzing the changes in insertion loss of slender structures. Furthermore, this FE approach is also appropriate for exploring various spatial configurations, without the difficulties encountered with analytical solution methods. A curvature parametrization based on avionics is introduced with the concepts of pitching and rolling angles, implemented with the aid of quaternions to avoid the rotation locking. Hence, the FE algorithm is applied in several different geometry configurations and the results are discussed. The configurations of spiral-eight and flat-bent springs found in the work of Søe-Knudsen are compared with the results obtained herein, for determining the accuracy of NuSim to represent stop-band frequencies. Finally, we show how to apply the same methodology on a full spring model, which considers its inactive coils, to show how easily NuSim can be employed to applications where an analytical response could be demanding.

High spatial resolution identification of hematoma in inhomogeneous head phantom using broadband fNIR system

This paper presents a novel method for early detection of hematomas using highly sensitive optical fNIR imaging methods based on broadband photon migration. The NIR experimental measurements of inhomogeneous multi-layer phantoms representing human head are compared to 3D numerical modeling over broadband frequencies of 30–1000 MHz. A finite element method (FEM) simulation of the head phantom are compared to measurements of insertion loss and phase using custom-designed broadband free space optical transmitter (Tx) and receiver (Rx) modules that are developed for photon migration at wavelengths of 670 nm, 795 nm, 850 nm, though results of 670 nm are discussed here. Standard error is used to compute error between 3D FEM modeling and experimental measurements by fitting experimental data to the asqrt {frequency} + b . Error results are shown at narrowband and broadband frequency modulation in order to have confidence in 3D numerical modeling. A novel method is established here to identify presence of hematoma based on first and second derivatives of changes in insertion loss and phase (∆IL and ∆IP), where frequency modulated photons sensitive to different sizes of hematoma is identified for wavelength of 670 nm. The high accuracy of this comparison provides confidence in optical bio-imaging and its eventual application to TBI detection.

Novel research on reliability of silica-based PLC optical splitters

Environmental, mechanical and optical reliability are basic premises for application of PLC optical splitters. According to temperature and humidity cycling experiment, it demonstrated that insertion loss of PLC optical splitter varies with temperature. Compared to performance at room temperature, the maximum insertion loss change of device is 0.472 dB at 75 °C, and 0.486 dB at −40 °C. A three-dimensional finite element model of PLC chip coupled with fiber array was established to study the effects of temperature on insertion loss. The simulation results match experimental results, indicating that misalignment of PLC chip and fiber array is the main reason for insertion loss change. It is significant to consider the influences of global temperature rather than only paying attention to performance at static temperature when we evaluate the reliability of PLC optical splitters.

Integrated athermal arrayed-waveguide grating multiplexer and demultiplexer with all-metal compensating rod for broadband temperature application.

In this paper, a unique device that can act as both multiplexer and demultiplexer is proposed with two all-metal compensating rods that makes the compensated chip almost the same spectrum profile as the original one. In this way a flat-top athermal arrayed-waveguide grating module of 100-GHz×40-ch is successfully fabricated. A small center wavelength shift of ±25 pm is achieved for the ultra-wide temperature range from -40°C to 85°C with the low insertion loss change of less than ±0.14 dB.

Fabrication of long range surface plasmon waveguide biosensors in a low-index fluoropolymer

The authors report the fabrication of long-range surface plasmon polariton biosensors consisting of thin narrow Au stripes embedded in a low refractive index fluoropolymer with etched fluidic channels. The fabrication process incorporates a sacrificial SiO2 channel etch stop layer to avoid waveguide damage and prevent channel over-etching, and an Al etch mask to minimize thermal cracking of the fluoropolymer during channel etching. Process details are reported along with fabrication results, and the optical and biosensing performance of the fabricated devices are demonstrated. The biosensors were tested for bulk sensitivity and bovine serum albumin (BSA) protein adsorption producing notable changes for solutions with different refractive indices (increment of 2 × 10−3) and a change in insertion loss of 0.1 dB as a monolayer of BSA forms on the device.

The biological acoustic sensor to record the interactions of the microbial cells with the phage antibodies in conducting suspensions

The acoustic biological sensor for the analysis of the bacterial cells in conducting suspension was developed. The sensor represented the two channel delay line based on the piezoelectric plate of Y-X lithium niobate thick of 0.2mm. Two pairs of the interdigital transducers (IDT) for the excitation and reception of shear horizontal acoustic wave of zero order (SH0) in each channel were deposited by the method of photolithography. One channel of the delay line was electrically shorted by the deposition of thin aluminum film between IDTs. The second channel remained as electrically open. The liquid container with the volume of 5ml was fixed on the plate surface between IDTs by the glue, which did not cause the additional insertion loss. For the first time the influence of the conductivity of the cell suspension on the registration of the specific and nonspecific interactions of the bacterial cells with phage-antibodies (phage-Abs) was studied by means of the developed sensor. The dependencies of the change in insertion loss and phase of the output signal on the conductivity of the buffer solution at specific/nonspecific interactions for the electrically open and shorted channels of the delay line were obtained. It was shown that the sensor successfully registered the interactions of microbial cells with phage-Abs in the range of the conductivity of 2–20 μS/cm on the model samples A. brasilense Sp245 – specific phage-Abs. The sensor in the time regime of the operation fast reacted on the specific/nonspecific interaction and the time of the stabilization of the output parameters did not exceed 10min.

Epitaxial VO2 thin film-based radio-frequency switches with thermal activation

In this paper, we report on the demonstration of thermally triggered “normally ON” radio-frequency (RF) switches based on epitaxial vanadium dioxide (VO2) thin films with a SnO2 template on (001) TiO2 substrates. Fast insulator-to-metal phase transition of the epitaxial VO2 at a relatively low temperature allowed RF switches made of the VO2 to exhibit sharp changes in the RF insertion loss during cooling and heating at 60 °C and 66 °C, respectively. The change of RF insertion loss due to phase transition is greater than 15 dB. The VO2 RF switches also completed the transition of S21 within less than 3 °C and showed a low-loss operation frequency of up to 24.2 GHz with a low insertion loss of −1.36 dB and isolation of 17.56 dB at 12.03 GHz, respectively. The demonstration suggests that epitaxial VO2-based RF switches can be used in switching elements up to Ku-band RF circuits.

Realization of a Low-Cost Displacement Sensor on PCB With Two-Metal-Layer Coplanar Waveguide Loaded by an EBG Structure

There are some difficulties in the realization of a microwave displacement sensor with conventional CPW loaded by electromagnetic bandgap structure on RF laminates with a regular printed circuit board manufacturing process. These difficulties have made this process impossible in practice. In this paper, for the first time, this kind of sensor has been implemented using a two-metal-layer (TML) CPW as a transmission line to overcome these difficulties. The proposed sensor consists of a TML CPW line loaded by two periodic-air-hole structures at both sides of the transmission line. Sliding the periodic structure at one side of the transmission line makes a change in the maximum insertion loss at the fundamental central frequency of the bandgap proportional to the length of the displacement. Analysis, finite-element method simulation, and fabrication have been carried out, and an average sensitivity of about 9 dB/mm and a dynamic range of 3 mm have been achieved for the 21 unit cells sensor with a period of 6 mm at 14.24 GHz. Furthermore, some practical issues, such as influence of the air gap between the metal traces and the movable structured dielectric on the sensor behavior and robustness of the sensor against the temperature variations, are practically investigated.

The acoustic sensor for rapid analysis of bacterial cells in the conductive suspensions

The possibility of using the acoustic sensor on the basis of a two-channel delay line for rapid analysis of bacterial cells in the conductive suspensions was investigated. The dependencies of change in phase and insertion loss of output signal of the sensor on conductivity of buffer solution with various concentrations of cells due to a specific interaction “bacterial cells - mini-antibodies” for electrically open and electrically shorted channels of delay line were measured. It has been found that these changes have the most values for the electrically open channel. It has been also shown that the sensor rapidly responds to the specific interaction and the time stabilization of the phase and insertion loss of output signal is less than 10min.

Simulation of SAW Humidity Sensors Based on ( 11 2 ¯ 0 ) ZnO/R-Sapphire Structures.

The characteristics of two types of surface acoustic waves SAWs (Rayleigh waves and Love waves) propagating in bilayered structures of ZnO/R-sapphire are simulated by a finite element method (FEM) model, in which both SAWs have crossed propagation directions. Furthermore, based on the bilayered structures, the frequency responses of Rayleigh wave and Love wave humidity sensors are also simulated. Meanwhile, the frequency shifts, insertion loss changes and then the sensitivities of both humidity sensors induced by the adsorbed water layer perturbations, including the mechanical and electrical factors, are calculated numerically. Generally, the characteristics and performances of both sensors are strongly dependent on the thickness of the ZnO films. By appropriate selecting the ratio of the film thickness to SAW wavelength for each kind of the sensors, the performances of both sensors can be optimized.

Modelling and Measurements of the Microwave Dielectric Properties of Microspheres

A microwave microstrip sensor incorporating a split ring resonator is presented in this paper for microsphere detection and dielectric characterization within a microfluidic channel. Split ring resonator (SRR) sensor of three different radii, but with approximately equal gap dimensions to change their sensitivity, were designed and fabricated, of resonance frequencies 2.5, 5.0 and 7.5 GHz. To validate the SRR sensors, two sizes of polystyrene microspheres were tested, of diameters 15 and 25 $\mu{\rm m}$ . Measurements of changes in resonance frequency and insertion loss of the odd SRR mode were related to the dielectric contrast provided by the microspheres and their host solvent, here water. COMSOL Multiphysics was used to model the sensors, and good agreements were found between the simulated and measured results.

Monolithic Crystal Filter for Application in Viscosity Sensor

Monolithic crystal filter (MCF) on AT-cut quartz for application in viscosity sensor was developed. After proper matching, at a frequency of $\sim 3.6$ MHz, insertion loss in air of $\sim 1.6$ dB was obtained. The linear coefficient of frequency of about −5 ppm/°C and changes of the insertion loss of $\sim 0.5$ dB, in the temperature range of 10°–80°, were obtained. To eliminate errors caused by the longitudinal acoustic wave generation, MCF should be immersed in a measured liquid or proper amount of liquid should be inserted into the sensing window. Using water and glycerin solutions, insertion loss changes against dynamic viscosity of the MCF were measured. In a viscosity range from about 1 to 1000 $\textrm {mPa}\cdot \textrm {s}$ , an insertion loss change of $\sim 24$ dB was obtained.