Optical Power Ratio Research Articles

Transmit-isolating photonic receivers with high isolation, large dynamic range based on reverse single-sideband modulation

Two kinds of transmit-isolating photonic receiver (TIPRx) systems with high isolation, large dynamic range based on reverse single-sideband (SSB) modulation are proposed and demonstrated. For the single dual-drive modulator (DD-MZM), the transmit signal allows less leakage of the RF power to the PD compared with the reverse double-sideband (DSB) modulation, thanks to the reduction in the number of the sidebands beating with the center carrier, while the forward DSB modulation benefits the high-quality response of the receive signal. Experimental results demonstrate that the average isolation is increased by 3–4 dB through suppressing the sideband intensity of the counter-propagation modulation, and the system has an isolation greater than 15 dB within 4–24 GHz. In addition, the spurious-free dynamic range (SFDR) of 98.31 dB·HZ2/3 is achieved. The parallel DD-MZMs scheme is put forward to improve the isolation and SFDR simultaneously, through the accurate cancellation of the reverse sidebands and third-order intermodulation (IMD3) components. The simulation result proves that the parallel architecture can suppress the reverse response and IMD3 effectively, and has the null of 0.10 for the isolation and the null of 0.20 for the IMD3 components when the optical power ratio is 0.9. The proposed technique can find applications in analog and digital communication.

Design and Analysis of the Dual-Band Far-Field Super-Resolution Metalens with Large Aperture.

The resolving power of metalens telescopes rely on their aperture size. Flat telescopes are advancing with the research on super-resolution confocal metalenses with large aperture. However, the aperture sizes of metalenses are usually bound within hundreds of micrometers due to computational and fabrication challenges, limiting their usage on practical optical devices like telescopes. In this work, we demonstrated a two-step designing method for the design of dual-band far-field super-resolution metalens with aperture sizes from the micro-scale to macro-scale. By utilizing two types of inserted unit cells, the phase profile of a dual-wavelength metalens with a small aperture of 100 μm was constructed. Through numerical simulation, the measured FWHM values of the focal spots of 5.81 μm and 6.81 μm at working wavelengths of 632.8 nm and 1265.6 nm were found to all be slightly smaller than the values of 0.61 λ/NA, demonstrating the super-resolution imaging of the designed metalens. By measuring the optical power ratio of the focal plane and the incident plane, the focusing efficiencies were 76% at 632.8 nm and 64% at 1265.6 nm. Based on the design method for small-aperture metalens, far-field imaging properties through the macro metalens with an aperture of 40 mm were simulated by using the Huygens-Fresnel principle. The simulation results demonstrate confocal far-field imaging behavior at the target wavelengths of 632.8 nm and 1265.6 nm, with a focal length of 200 mm. The design method for dual-band far-field super-resolution metalens with a large aperture opens a door towards the practical applications in the dual-band space telescope system.

Performance analysis of all-optical 1-bit comparator using 2D-PhC nonlinear ring resonators based on threshold switching method

ABSTRACTIn this research, an all-optical 1-bit comparator (AOCMP) is designed using two-dimensional photonic crystals (2D-PhCs) nonlinear ring resonators (NRRs), and its performance is analyzed based on the threshold switching method. By optimizing the structural parameters of NRRs, such as the refractive index and radius of the rods, this resonator can operate with desired wavelength (1550 nm) within the operating frequency range determined by the transverse magnetic (TM) band diagram. The performance of the proposed AOCMP is analyzed in terms of various factors such as optical switching power, bit rate, time delay, and ON-OFF contrast ratio that are calculated using a finite difference time domain (FDTD) simulation. Also, the operating frequency range (the wavelength range of 1355–2178 (nm)) is investigated using the plane wave expansion (PWE) method. The optimized optical device has exhibited a high contrast ratio of 10.36 dB within a very small size of 325 μm2.

Simultaneous OSNR and chromatic dispersion monitoring based on optical tones power ratio

A novel technique is proposed for simultaneous monitoring of optical signal-to-noise ratio (OSNR) and chromatic dispersion (CD). The scheme is based on the cross-phase modulation effect in a highly nonlinear fiber, which induces a change in the optical tones according to the impairments. The power ratio of the optical tones at two separate frequencies is utilized for monitoring. Improvements in the maximum measurable OSNR, CD and dynamic range can be obtained using only the clock tone for the non-return-to-zero, return-to-zero with a 50% duty cycle differential quadrature phase-shift keying, differential phase-shift keying and on-off keying signals at 80 Gb/s. For the return to zero differential quadrature phase shift keying (RZ-DQPSK) system, the OSNR of 4–40 dB can be monitored with a 36.73 dB dynamic range, and a chromatic dispersion of 0–117 ps/nm can be monitored with a 48.68 dB dynamic range. A correlation is built to describe the relationship of the power ratio with the OSNR and chromatic dispersion which has a root-mean-squared error of 1.41. The delay group dispersion insensitivity, the impact of the input signal power, and the filter selection are investigated. The design enables accurate monitoring, simple operation and may be used in a wide range.

Bidirectional Cladding-Pumped Multicore EDFA and its Optimization for Energy Efficiency by Tuning Pump Condition

This work investigates the feasibility of improving the energy efficiency of a cladding-pumped multicore (MC) EDFA by utilizing bidirectional (BD) pumping. We combined a conventional forward-cladding-pumped MC-EDFA with backward cladding pumping and tuned the pump-gain characteristics and gain shape by controlling the optical pump power ratio of its forward and backward pumps. Since EDFAs have wavelength dependence, output power equalization by each wavelength channel is extremely important for amplifying the wavelength division multiplexing (WDM) signal. The standard method of current equalization is to adjust the attenuation by the output power of each wavelength channel. The main issue with the current standard equalization is the indispensable optical power loss caused the reduced optical amplification efficiency of the EDFA. Our previous work demonstrated that the optical power loss due to equalization can be reduced by controlling the optical power ratio of the forward and backward pumps. This leads to improved energy efficiency of the signal amplification and equalization of both the WDM and spatial division multiplexing (SDM). <p xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">In this paper, we report our detailed investigation into the tuning amplification characteristics of the BD-MC-EDFA. Our main focus was the gain, noise figure (NF), and gain shape of a 7-core BD-MC-EDFA prototype when forward and backward optical pump power was changed. Under 8 W of total optical pump power, the percentage of 60% forward cladding optical pump power was found to be optimal for efficiency considering the minimum output optical power loss due to equalization. This condition translates into a 1.7% pump conversion efficiency (PCE) improvement, which corresponds to a 24% reduction of the total optical pump power compared to conventional MC-EDFA with only forward cladding pumping. Although the NF deteriorated by 1.0 dB in wavelength average in the 4.5-THz signal bandwidth in exchange for the efficiency improvement, degradation of the 34.2-GBaud polarization multiplexed 16 quadrature amplitude modulation (PM-16QAM) signal amplified by the BD-MC-EDFA operated under the optimized condition was negligible.

Spectra reconfiguration of a silicon microring resonator via double injection with different angles.

A reconfigurable silicon microring filter, which is constructed by cascading a tunable Mach-Zehnder interferometer and a double injected silicon microring resonator with a variable input angle, is proposed and investigated. The spectra reconfigurations of the optical filter were simulated and analyzed using the transmission matrix method. The results show that when keeping the perimeter of the microring constant, the free spectral range (FSR) of the filter can be multiplied by adjusting the angle between the two injections. Moreover, by changing the coupling coefficients of the microring and the optical power ratio between the two injections, different types of spectral responses such as square, sinusoidal, and flat-top interleaver can be obtained. The device is simple and easy to integrate, and its capabilities to expand the FSR and spectral reconfiguration may have great potential in reconfigurable integrated optic chips.

Multiple-input hybrid plasmonic OR logic gate with a nanostructure.

A multiple-input hybrid plasmonic OR logic gate has been constructed, analyzed, and simulated utilizing the finite element method by using the COMSOL software package version 5.5. To realize the suggested three- and four-input hybrid plasmonic OR gate, constructive and destructive interference has been standard among the input ports and control port. The factors used to evaluate the functionality of the nanoscale gate are the contrast ratio, modulation depth (MD), and insertion losses (ILs). In contrast, the optical power ratio at the output port, known as the transmission value (T value), has been measured and used to distinguish between logic 1 (ON-state) and logic 0 (OFF-state). The transmission threshold value in this article was 25%, and the wavelength range considered to display the result was from 1000 to 2000nm. The three-input hybrid OR gate occupied a size of 500n m×400n m with transmission amplification results from the best T value of 216.5 % with 98.85% as a MD. In comparison, the four-input OR gate comes with a size of 600n m×400n m at the best T value of 301.5%, supported by a 99.33% as the MD. The IL values for the three-input and four-input designs are -4.07 and -5.4d B, respectively. The system resonance wavelength is 1310nm.

Multi-primary human-centric lighting based on the optical power ratio and the CCT super-smooth switching algorithms

The discovery of intrinsically photosensitive retinal ganglion cells related to circadian rhythms has led to an increased research focus on the physiological and psychological effects of artificial lighting sources, with the emerging concept of human-centric lighting. This study tuned the spectra of a six-primary lighting source based on pulse width modulation to obtain the best visual and non-visual performances in work, leisure, and daytime indoor applications. The adopted method uses indicators, including the circadian action factor, goodness-of-fit coefficient, color rendering index, and correlated color temperature (CCT). Among these, a CCT super-smooth switching algorithm has been proposed to achieve the change trajectory of the chromaticity coordinates in the Commission Internationale de L'Eclairage color diagram close to the blackbody radiation curve during the CCT switching process in different cases. Finally, this study can provide useful guidance for improving light qualities and achieving human-centric lighting based on a six-primary lighting source with light-emitting diodes.

Optimization of intensity interrogation method in cascaded double-ring sensors

A higher-sensitivity optical sensor based on cascaded double-ring resonators (CDRR) for intensity interrogation has been demonstrated. By detecting the output optical power ratio between the drop port and coupling port and reducing the free spectral range for difference (ΔFSR), the intensity interrogation sensitivity of the CDRR sensor can be improved by 2.15 times.

Real-Time Tunable Optofluidic Splitter via Two Laminar Flow Streams in a Microchannel.

This paper reports a tunable optofluidic splitter in which the incident light is split via refraction and reflection at the interface between two laminar flows in a microchannel but with different refractive indices. A Y-junction microchannel is used to demonstrate the continuous tuning of the splitting ratio of optical power by smooth adjustment of the ratio of two flow rates. In addition, it has achieved the tuning of split angle from 5° to 19° by the control of the refractive index contrast. The dynamic response gives a fastest switching frequency of 1.67 Hz between the “wave-guiding” and “splitting” status.

Instantaneous Frequency Measurement With Full FSR Range and Optimized Estimation Error

A photonic-assisted approach for instantaneous frequency measurement (IFM) based on a 1×4 Mach–Zehnder interferometer (MZI) structure is proposed and experimentally demonstrated. In this IFM method, a Mach–Zehnder modulator (MZM) in conjunction with an optical filter play the role of CS-SSB signal generator, mapping the unknown microwave into a tunable optical sideband. Due to the property of the subsequent 1×4 MZI structure, two amplitude comparison function (ACF) that convert the frequency information into optical power ratio can be established. A detailed theoretical analysis illustrates the realization of frequency measurement with a range of full free spectral range (FSR) and optimized estimation error by using these two ACFs. Simulation has been carried out to verify the mechanism, and the discussion about the merits of CS-SSB modulation and the applicable scenarios is also given. A proof-of-concept experiment is performed, in which the microwave frequency measurement from 7.5 to 20 GHz is demonstrated with an estimation error of less than 100 MHz.

New structure for an all-optical logic gate based on hybrid plasmonic square-shaped nanoring resonators and strips

Seven all-optical logic gates based on hybrid plasmonic squared-shaped nanoring resonators and strips are proposed, designed, and numerically analyzed using finite element method with COMSOL software package version 5.5. Constructive and destructive interferences between the input port(s) and the control port(s) are the main operating principles used to produce the proposed gates. The ratio of output optical power to the input power at a single port which is called the transmission threshold is selected to be 30% and the resonance wavelength is 1310 nm. All the hybrid plasmonic logic gates are performed in a single structure of 400 nm × 400 nm dimensions and the performance is measured according to the values of transmission at the output port versus a wavelength range from 800 to 2000 nm, contrast ratio, modulation depth, and insertion loss. The transmission exceeds 100% in five gates, 146% at NOT and NAND gates, 202.3% at OR, AND, and XNOR gates. The modulation depth scores are 99.75% at the XNOR gate, 98.5% at the NOR gate, 97.67% at OR, AND, NOT, and NAND gates, and 95.29% for the XOR gate.

ANALYSIS OF CORNEAL ANTEROPOSTERIOR RATIO OF OPTICAL POWER USING OCT.

The aim of the study was to analyse the values of the anteroposterior corneal optical power ratio (AP ratio), to compare the resulting values with those of theoretical models of the eye, and to define the effect of using an individual ratio value on the approximation of the total corneal power. A total of 406 eyes were included. Each patient underwent an OCT (RTVue XR) examination, according to which the AP ratio of the cornea was determined, as well as the biometric parameters of the eye (Lenstar LS900). The correlation between the biometric parameters of the eye and the individual AP ratio values was evaluated using Pearsons correlation coefficient. In the analysis, the AP ratio results were compared with selected schematic models of the eye. Using Gaussian equations, a theoretical calculation of the total corneal optical power (KG) was performed, by fitting the AP ratio value and comparing it with the actually measured total corneal power (TCP). The mean value of the individually determined AP ratio was 1.17 ±0.02. The most frequently represented interval (33.74 %) was 1.17 to 1.18 AP ratio values, with the vast majority of eyes (79.56 %) in the range of 1.15 to 1.20. Individual values of total corneal optical power were statistically significantly different (p &lt; 0.05) from the theoretical values of TCP (except in the Liu-Brennan eye model, where p = 0.06). The lowest mean difference of values was found for the Navarro schematic model. The dependence of the measured AP ratio values and biometric parameters reached a moderate negative correlation (r = -0.50 for p &lt; 0.05) with the parameter corneal posterior surface curvature (Rp), as well as a weak negative correlation with limbal diameter WtW (r = -0.26 for p &lt; 0.05) and a weak positive correlation with central corneal thickness CCT (r = 0.17 for p &lt; 0.05). The assumption of a constant value of the AP ratio according to the selected schematic models of the eye is statistically significantly different from the actual measured values and was defined to have only a negative weak correlation with the size of the limbus diameter. Using the resulting average value of the determined AP ratio (1.17 ±0.02), a lower difference between real and calculated total corneal optical power was achieved.

Accumulation, Directional Delivery and Release of Nanoparticles along a Nanofiber.

Controllably accumulating and delivering nanoparticles (NPs) into specific locations are a central theme of nano-engineering and important for targeted therapy or bacteria removal. Here we present a technique allowing bidirectional accumulation, directional delivery and release of nanoparticles through two 980-nm-wavelength counter-propagating evanescent waves in an optical nanofiber (NF). Using 713-nm-diameter polystyrene NPs suspension and an 890-nm-diameter NF as an example, we experimentally and theoretically demonstrate that the NPs delivered along the NF surface in opposite directions are accumulated into the region where the scattering loss of the NPs is maximum, and about 90% of the incident optical field from both ends of the NF can be coupled into the region. Moreover, the accumulation region can be controlled by altering the incident optical power ratio of the two counter-propagating laser beams, while the accumulated NPs can be delivered and then released into the specific locations by turning off the two lasers.

Secure and noise-resistant underwater wireless optical communication based on spectrum spread and encrypted OFDM modulation.

In addition to requirements on increasing transmission distance and bitrate, the study of underwater wireless optical communication (UWOC) is also facing limitations and challenges, such as interference induced by background noise, demand of higher receiver sensitivity, and communication security issues. In this paper, we experimentally demonstrate a physical layer secure and noise-resistant UWOC system based on spectrum spread and encrypted orthogonal frequency division multiplexing (SSE-OFDM) modulation, transmission through a 14.2 m sediment circulating water tank. Firstly, experimental results show that the required optical power ratio of signal and noise light (OPR) for QPSK signal under BER threshold of 3.8×10-3 is around -5.77 dB for a spectrum spread factor (N) of 100, with a signal-to-noise ratio (SNR) improvement of 19.06 dB. Secondly, without the background noise interference, the receiver sensitivity is also improved from -50 dBm to -62.4 dBm by using the SSE-OFDM modulation, achieving a maximum attenuation length (AL) of 19.67. Thirdly, physical layer security of UWOC can also be realized, which suppresses the SNR of eavesdropper to -3.72 dB while improving SNR of the authorized receiver to 17.56 dB under the condition of no leakage of keys. Additionally, analytical expressions for SSE-OFDM based UWOC performance are also derived, which agree well with the experimental results. Based on the analytical expressions, the maximum secrecy capacity Cs for SSE-OFDM based UWOC system under eavesdropping can be obtained by optimizing the intentionally inserted artificial noise power ratio and the spectrum spread factor N.

Adaptive feedback threshold based demodulation for mobile visible light communication and positioning integrated system.

In this paper, a novel adaptive feedback threshold (AFT) based demodulation for mobile visible light communication and positioning (VLCP) integrated system is proposed. The AFT can vary with the received signal without excessive fluctuation and support communication and positioning in mobile environment. For the VLCP integrated system with single light emitting diodes (LED) and multiple photodetectors (PDs), maximal ratio combining (MRC) and received optical power ratio (ROPR) based on the AFT is further achieved for communication and positioning with high performance, respectively. It is demonstrated that high credible communication and high accuracy positioning for the mobile integrated VLCP system can be realized by using the proposed AFT based demodulation. As a result, the implemented VLCP system with a moving speed of 1 m/s is evaluated experimentally. Average positioning error of 3.43 cm with 800 mA current and the bit error ratio (BER) with different currents are also obtained.

Design and spectral analysis of mixed-carrier communication for sixth-generation networks.

The fifth-generation (5G) wireless cellular network is expected to be ready for commercialization within this year. The huge spectrum enabled by the millimetre-wave (mm-Wave) technology is expected to introduce a hype in data usage per user. The 5G is also expected to concurrently support a wide variety of services; however, the practical trade-offs associated with concurrent services require further investigations. In this work, a physical layer (PHY) design to support visible light communications is considered to efficiently support concurrent services that are essential to serve the needs of the sixth-generation (6G) network. A novel communication technique, i.e. mixed-carrier communication (MCC), is proposed. MCC enables simultaneous wireless services such as broadband access, low-rate internet-of-things connectivity, device-free sensing, and device-based localization. This study presents, firstly, a thorough investigation of the design procedure of the novel MCC PHY, secondly, the spectral profile of MCC towards proper spectrum management and interference analysis, and thirdly, performance evaluation based on modelling, simulation and an experimental proof-of-concept. The design steps recommend that the system performance degrades beyond a signal-to-noise ratio (SNR) threshold. For instance, SNR of 25.1 dB and 2.6652 optical power ratio between the communications signal and the driving envelope, for 64-quadrature amplitude modulation (64-QAM), are recommended to avoid performance degradation due to clipping. Simulation results show an interference-immune performance of a properly managed spectrum. For a bit-error-rate (BER) of 10-3, an SNR penalty of 2-5 dB is observed for different interference scenarios. The experimental measurements illustrate a high-quality signal of 21 dB SNR at 50 cm and 10-3 BER using 64-QAM.

Measurement of Instantaneous Microwave Frequency by Optical Power Monitoring Based on Polarization Interference

A photonic-assisted approach for instantaneous frequency measurement based on optical power monitoring is proposed and demonstrated. Instead of using optical filter, a dual-polarization Mach–Zehnder modulator is used to modulate the unknown RF signal with a designed electrical time delay. Due to the property of electrical time delay, the frequency information is firstly converted to phase shift and then to the optical power. By monitoring the optical power, a monotonic relationship between the incident microwave frequency and optical power ratio can be easily established. A detailed theoretical analysis is carried out to illustrate the mechanism of the proposed instantaneous frequency measurement setup. Simulation has been performed to investigate the tuning of measurement range and the impact of imperfection devices. A proof-of-concept experiment has been carried out to verify the mechanism.

Indoor visible light high precision three-dimensional positioning algorithm based on single LED lamp

With the rapid development of information technology, there is a growing demand for people in indoor location services.This paper proposes a novel high-precision indoor three-dimensional positioning algorithm for single light emitting diode (LED). By using three tilted photodetectors (PD)and one horizontal PD as receivers.Calculating the ratio of received optical power of the three tilted PDs to the horizontal PD respectively. According to the relationship of position between the PDs and the tilt angle, azimuth angle, placement angle of the tilted PD and other parameters, establish a mathematical relationship between the received optical power ratio and the receiver's three-dimensional coordinates, calculate the three-dimensional coordinates of the receiver at any position. The simulation results show that in the positioning area of 1 × 1 × 1.5 m3, when the inclination angle α is 25°, the azimuth angle difference θ is 90°, the placement angle ω1=0°, ω2=90°, ω3=180°, the distance r between the horizontal PD center and the tilted PD center is 1 cm, the positioning accuracy is better, the point with the positioning error within 3 cm accounts for 84 % of the total test points, and the average positioning error is 2.52 cm. Compared with the traditional indoor positioning technology, the cost of the positioning technology used in this paper is greatly reduced, the positioning accuracy is significantly improved,and can get three-dimensional coordinates.

Optical adaptive filtering for Doppler shift simulator

Based on free space laser communication, this article describes the working principle of electro-optical frequency shifting, designs an optical adaptive filtering module, and builds the core module of the dynamic optical Doppler shifting simulator for laser channel. It is expected to be applied to the heaven-ground integrated communication link. In this article, we adopt the electro-optical frequency shifting technique combined with the microwave-light wave. In the 1 550 nm band, the negative feedback algorithm is used to complete the adaptive filtering, which realizes optical Doppler frequency shifting and high-precision locking. The frequency shift range reaches +5.5–+32 GHz, and the analog precision is better than 645 Hz. When the microwave frequency is greater than 13.5 GHz, the signal-to-noise ratio (SNR) of the output optical power reaches 20 dB, which lays the foundation for the next stage space laser communication.