Optical Beamforming Research Articles

Optical Beamforming tuning with Genetic Algorithm and Deep Learning

Optical Beamforming tuning with Genetic Algorithm and Deep Learning

Compact Optical Beamforming Chip Using Broadband Continuously Tunable Delay Lines

Compact Optical Beamforming Chip Using Broadband Continuously Tunable Delay Lines

Reconfigurable Microwave Multi-Beamforming Based on Optical Switching and Distributing Network

Optical beamforming in microwave photonics is promising for supporting broadband wireless communications. However, the current optical beamforming lacks freedom because of the fixed connection between radio frequency (RF) signal and antenna elements (AEs). This manuscript tackles this challenge by proposing a dynamical optical beamforming architecture that reconfigures the antenna subarray for signal transmission depending on the number of signals to be transmitted. The proposed architecture employs an optical switching and distributing network (SDN) to realize a flexible connection between signals and AEs. An instance of the proposed architecture in photonic integrated circuits, which enables three working modes and transmits four RF signals through sixteen AEs, was presented and numerically simulated. The optical field distribution and beam pattern plots illustrated the operational principle and validated the feasibility of the proposed SDN architecture. Furthermore, the impact of the introduced architecture on the signal amplitude–phase consistency and the comparison of the proposed dynamic architecture and conventional fixe architectures are analyzed and discussed. The results indicate that the proposed architecture exhibits variable beamforming gain with lower hardware complexity.

Millimeter-Wave and Sub-THz Phased-Array Imaging Systems Based on Electro-Optic Up-Conversion and Optical Beamforming

Millimeter-Wave and Sub-THz Phased-Array Imaging Systems Based on Electro-Optic Up-Conversion and Optical Beamforming

A novel hemispherical visible light transmitter design for multi-user optical beamforming in wireless communication

A novel hemispherical visible light transmitter design for multi-user optical beamforming in wireless communication

Spatial and Polarization Division Multiplexing Harnessing On‐Chip Optical Beam Forming

AbstractOn‐chip spatial and polarization multiplexing has emerged as a powerful strategy to boost the data transmission capacity of integrated optical transceivers. State‐of‐the‐art multiplexers require accurate control of the relative phase or the spatial distribution among different guided optical modes, seriously compromising the optical transmission bandwidth and performance of the devices. To overcome this limitation, a new approach based on the coupling between guided modes in integrated waveguides and optical beams free‐propagating on the chip plane is proposed. The engineering of the evanescent coupling between the guided modes and free‐propagating beams allows spatial and polarization multiplexing with state‐of‐the‐art performance. A two‐polarization multiplexed link and a three‐mode multiplexed link using standard 220‐nm‐thick silicon‐on‐insulator technology have been developed. The two‐polarization link shows a measured −35 dB crosstalk bandwidth of 180 nm, while the three‐mode link exhibits a −20 dB crosstalk bandwidth of 195 nm. These links are used to demonstrate error‐free operation (bit‐error‐rate <10−9) in multiplexing and demultiplexing of two and three non‐return‐to‐zero signals at 40 Gbps each, with power penalties below 0.08 and 1.5 dB for the two‐polarization and three‐mode links, respectively. The approach demonstrated for two polarizations and three modes is transferable to future implementation of more complex multiplexing schemes.

Optical Beamforming Networks for Millimeter-Wave Wireless Communications

With the rapid data growth driven by smart phone, high-definition television and virtual reality/augmented reality devices and so on, the launched 5G and upcoming 6G wireless communications tend to utilize millimeter wave (mmWave) to achieve broad bandwidth. In order to compensate for the high propagation loss in mmWave wireless communications and track the moving users, beamforming and beamsteering are indispensable enabling technologies. These have promising potential to be realized through the use of optical beamforming networks (OBFNs) that have a wider bandwidth and smaller size, lower power consumption, and lower loss compared to those of their electric counterparts. In this paper, we systematically review various OBFN architectures using true time delays and optical phase shifters, as well as discuss performances of different architectures, scalable technologies that promote the advancement of OBFNs, and the application potentials of OBFNs. Two-dimensional OBFNs with discrete components or integrated optical devices have been elaborated, in addition to one-dimensional architectures. Moreover, the state-of-the-art technologies relative to reducing the size, loss and nonlinearity of OBFNs have also been discussed here.

Optical Beamforming System Based on Polarization Manipulation With Amplitude–Phase Coupling Suppression

Traditional phased arrays based on phase shifters suffer severely from the beam-squint problem when operating at the wideband mode. Optical beamforming is one feasible solution for broadband beam steering, of which the performance, however, is affected by the amplitude–phase coupling. To solve this problem, we propose an optical beamforming system with amplitude–phase coupling suppression based on polarization manipulation. A polarization controller is used to control the transmission of carrier light along the fast or slow axis in the polarization-maintaining fiber. As there is a fixed transmission time difference between the two orthogonal modes, the phase adjustment can be achieved with low amplitude variation because of the low polarization-dependent loss. In addition, the intensity of the signal can be controlled using a polarizer with negligible phase variation, realizing amplitude control with low phase coupling. Experimental results show that the amplitude–phase coupling coefficient is about 5.8 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times$</tex-math> </inline-formula> 10 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{-3}$</tex-math> </inline-formula> ps/dB, while the phase–amplitude coupling is less than 7.5 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times$</tex-math> </inline-formula> 10 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{{-3}}$</tex-math> </inline-formula> dB/ps. The performance of the optical beamforming is analyzed by numerical simulation and proof-of-concept experiment, showing that the beam pointing deflection is less than 0.1 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\circ}$</tex-math> </inline-formula> , while the main-lobe-to-sidelobe suppression ratio deteriorates less than 1 dB when the beam scans from 0 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\circ}$</tex-math> </inline-formula> to 45 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\circ}$</tex-math> </inline-formula> .

Enhanced secrecy outage probability for multiple‐input single‐output‐VLC systems through optical beamforming and improved light emitting diodes deployment

AbstractThe authors propose to arrange the light emitting diodes (LEDs) on the ceiling for an indoor visible light communication system in order to minimise the secrecy outage probability (SOP) at the location of the legitimate user (LU). More precisely, by deriving the secrecy capacity for a multiple‐input single‐output‐VLC system, we evaluate the SOP at the LU's location which is used as the appropriate metric to determine the position of the LEDs on the ceiling. To mitigate the effect of the eavesdropper, we derive the optimal beamforming coefficients which are used at the transmitter LED array with the aim of maximising the signal‐to‐noise ratio at the LU. Simulation results show that for a SOP of 10−4, the proposed SOP‐based LED arrangement with optimal beamforming offers up to 3 dB gain in transmit power compared to the classical uniform LED arrangement with sub‐optimal zero‐forcing beamforming. Moreover, they show that by using the proposed method, the SOP is kept below a desired threshold, over a wider area inside the indoor environment compared to classical methods.

Impact of Polarization on Distributed Optical Beamforming

In this letter, we propose the concept of distributed optical beamforming and its feasibility requirements. We quantify the importance of polarization beamforming among the beams for maximized beamforming. As a first step towards distributed polarization beamforming (DPolB), in this work we consider coplanar sources and receiver for beamforming and demonstrate the critical requirement of polarization alignment for maximized beamforming gain. We determine theoretically and verify via simulations the optimal polarization angle at the sources such that the electromagnetic waves interfere constructively at the receiver. Subsequently, we propose a novel method for automated polarization beamforming of multiple optical beams independent of source locations. Performance of the proposed DPolB is analytically captured in terms of average beamforming gain and verified using simulations. We also verify that the reduction in gain caused by slight deviation from coplanarity is not significant.

Solid-state 360° optical beamforming for reconfigurable multicast optical wireless communications.

Optical wireless communication is an attractive technique for data center interconnects due to its low latency line-of-sight connectivity. Multicast, on the other hand, is an important data center network function that can improve traffic throughput, reduce latency, and make efficient use of network resources. To enable reconfigurable multicast in data center optical wireless networks, we propose a novel 360° optical beamforming scheme based on the principle of superposition of orbital angular momentum modes, emitting beams from the source rack pointing towards any combination of other racks so that connections are established between the source and multiple destination racks. We experimentally demonstrate the scheme using solid state devices for a scenario where racks are arranged in a hexagonal formation in which a source rack can connect with any number of adjacent racks simultaneously, with each link transmitting 70 Gb/s on-off-keying modulations at bit error rates of <10-6 at 1.5-m and 2.0-m link distances.

Incoherent Optical Beamformer for ARoF Fronthaul in Mm-Wave 5G/6G Networks

Analog beamforming is a key technology to enable millimeter-wave (mm-wave) mobile communications. Nonetheless, the most widespread beamforming solutions are based on electrical implementation, which is inefficient in terms of power consumption, signal bandwidth, and losses. Optical beamforming is a promising alternative for future mm-wave mobile communications due to its inherent benefits, such as large bandwidth, low cross-talk, and low losses. Optical beamforming networks (OBFN) are an outstanding technique to simultaneously generate and radiate multiple beams in an effective manner. True time delays (TTDs) based on optical waveguides are an attractive solution since they offer constant delay in the spectrum to avoid beam squint and allow highly scalable OBFN implementation. In this work, for the first time to the best of the authors' knowledge, an incoherent 4x4 OBFN based on optical waveguides and capable of simultaneously generating four beams is presented, including a thorough explanation of its operating principles and providing a detailed characterization. The presented OBFN is fabricated on Si <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$_{3}$</tex-math></inline-formula> N <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$_{4}$</tex-math></inline-formula> photonic integrated circuit (PIC), and designed for transmission at 27.5 GHz, within the n257 5G band. Furthermore, the building blocks forming the OBFN PIC are deeply explained, providing their corresponding theoretical formulation and key design parameters. The fabricated PIC is exhaustively characterized through all its building blocks, showing in detail the realized measurement procedure. The experimental measures match the design parameters with minimal error, showing the feasibility of fabricating future OBFNs with the same technology and topology for larger antenna arrays. The experimental results corroborate the viability of the presented OBFN architecture as an excellent technology to consider in future mm-wave 5G/6G networks. The contribution of this work paves the road to turn optical beamforming into a mature, scalable, and efficient technology.

Spaceborne Multibeam Phased Array Antennas for Satellite Communications

Multibeam phased array antenna is one of the core payloads of the satellite communication system, which has the potential to realize the transformation of the satellite communication system from application-adapted satellite to satellite-adapted application. This article provides a brief overview of the beamforming technologies used in spaceborne multibeam phased array antennas from three perspectives: analog beamforming, digital beamforming, and optical beamforming. The application status of multibeam phased array antennas in satellite communication is then classified and explained. Finally, the development trend of spaceborne multibeam phased array antenna is analyzed.

Two-Dimensional Phased-Array Receiver Based on Integrated Silicon True Time Delay Lines

In this work, we first demonstrate a complete 2-D photonics-aided phased-array antenna (PAA) receiver with so far the largest scale of 8 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> 8 by utilizing highly integrated silicon true-time delay line chips. The prototype utilizes the wavelength-division-multiplexing technology to build the crucial optical beamforming network (OBFN) module so as to dramatically reduce the type and amount of silicon binary integrated optical time delay lines. The measured beam scanning range in the frequency range from 2 to 6 GHz is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$90^{\circ }\,\,\times \,\,90^{\circ }$ </tex-math></inline-formula> with a beam-pointing step of 1°. Furthermore, due to the online channelized signal processing module, we systematically characterize sensitivity, RF gain, and dynamic range of the photonics-aided PAA. Considering that we first utilize the photonic integration technology to realize a 2-D PAA demonstrator with the largest scale and the highest technological maturity, we believe that it presents a milestone in the development of future microwave photonics-based radar systems.

Air-Filled SIW Remote Antenna Unit With True Time Delay Optical Beamforming for mmWave-Over-Fiber Systems

A low-complexity and efficient mmWave-over-fiber remote antenna unit (RAU) is proposed for broadband transmission and wide-angle squint-free beam steering in the full [26.5–29.5] GHz n257 5G band. It leverages an optical beamforming network (OBFN), implemented on a silicon photonics integrated circuit, and a broadband optically enabled 1x4 uniform linear array (ULA). The antenna elements (AEs) of the ULA are implemented in air-filled substrate-integrated-waveguide technology. They adopt an improved aperture-coupled feeding scheme to achieve high efficiency, high isolation and minimal back radiation over a broad frequency band. Each AE is compactly integrated and co-optimized with a dedicated opto-electrical transmit chain, maximizing the RAU’s performance, including beamforming flexibility and energy efficiency, while minimizing its size. The separately packaged OBFN implements true-time-delay beamforming by means of four switchable optical delay lines that are capable of discretely tuning the delay difference between AEs with a resolution of 1.6 ps, up to a maximum delay of 49.6 ps to fully exploit the ULA’s full grating-lobe-free scan range. The measured AEs are excellently matched in the [25.1–30.75] GHz band, exhibit high isolation ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ &gt;$</tex-math></inline-formula> 15 dB) in the operating band, and feature a stable peak gain of 6.8 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\pm$</tex-math></inline-formula> 0.72 dBi with a beamwidth of at least 95 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^\circ$</tex-math></inline-formula> . Additionally, optical beamforming was successfully demonstrated by steering the RAU’s beam towards angles up to 51.8 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^\circ$</tex-math></inline-formula> without grating lobes. The optically enabled 1 × 4 ULA successfully establishes a 64-QAM wireless communication link at 2.2 Gbaud (13.2 Gbps) while beam steering up to 50 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ ^\circ$</tex-math></inline-formula> with an error vector magnitude below 7.6%.

Broadband 1×8 Optical Beamforming Network Based on Anti-resonant Microring Delay Lines

We demonstrate a 1×8 binary tree optical beamforming network (OBFN) chip for a microwave photonic phased array antenna. The OBFN is formed by cascading multiple microring resonators (MRRs) working at the anti-resonant wavelengths. The binary tree topology reduces the MRR amount by reusing the MRRs in the preceding stage, and the anti-resonant MRRs realize continuous delay tuning with a reduced in-band delay fluctuation. The delay adjustment is achieved by digitally tuned MRRs and one continuously tuned MRR in each stage with an improved operating bandwidth. The random initial states of the MRRs are calibrated to produce a flat delay response. Experimental results show that the maximum delay is 560 ps. The beamforming performance of the OBFN is evaluated in 20 ps and 45 ps delay increments. In an 8-GHz operating bandwidth, the maximum delay fluctuation is less than 7.6 ps. The capability of our delay lines to suppress the delay ripple encountered in conventional on-resonance delay lines opens exciting opportunities for the development of compact integrated broadband OBFNs demanded in broadband microwave phased array antennas.

Optical Generation and Transmission of mmWave Signals in 5G ERA: Experimental Evaluation Paradigm

We demonstrate the generation, of a mmWave signal via the injection of an optical frequency comb (OFC) into an integrated tunable dual distributed Bragg reflector (DBR) laser as well as the fiber transmission and the processing of this signal by an optical beamforming network (OBFN). The dual DBR laser is based on a hybrid indium phosphide (InP) – polymer photonic integrated circuit (PIC). Two different cases have been examined in which the microwave signal is centered around 39 GHz and 60 GHz respectively, carrying quadrature amplitude modulation (QAM) formats at 0.5 Gbaud. In this proof-of-concept scenario, the OBFN consists of two optical paths, where the relative true time delay is induced by an optical delay line (ODL). Extensive comparison between the back-to-back (B2B) case and scenarios with transmission over 25 km of standard single-mode fiber (SSMF) has been made using the error-vector magnitude (EVM) and the bit-error ratio (BER) as evaluation criteria. In all cases, error-free transmission was suggested for all QPSK signals, whereas a worst-case EVM of 11.8% was observed for 16-QAM transmission, successfully showcasing the concept’s potential. The generated microwave signal’s frequency can be set arbitrarily high, provided that high-speed photodetection equipment is available for the detection and down-conversion of the signal. Extension to higher antenna elements (AEs) numbers is straight-forward, relying only on the number of available photodetectors.

Experimental demonstration of dispersion-diversity multicore fiber optical beamforming.

Phased array antenna (PAA) beam-steering in high radiofrequency bands will be key for upcoming 5G & Beyond wireless communications systems. As a compact and efficient solution to provide tunable beam steering simultaneously to parallel antenna distribution and connectivity, we experimentally demonstrate, for the first time to our knowledge, tunable optical beamforming implemented on a dispersion-diversity multicore optical fiber. The uniqueness of this fiber lies in the fact that each one of its seven step-index trench-assisted cores has been tailored to provide the required chromatic dispersion to enable tunable optical true-time delay line operation. Continuous 1D beam-steering was demonstrated by measuring the radiating pattern of an in-house fabricated 8-element PAA in an anechoic chamber at the radiofrequency of 26 GHz, sweeping the beam-pointing angle from -43° up to 40° by varying the operating optical wavelength from 1542.50 up to 1548.28 nm. Next-generation fiber-wireless communications systems will benefit from the demonstrated dispersion-diversity MCF optical beamforming in terms of flexibility, versatility, capacity, and connectivity along with reduced size, weight, and power consumption.

Liquid crystal lens set in augmented reality systems and virtual reality systems for rapidly varifocal images and vision correction: erratum.

We have an addendum for our previous paper [Opt. Express30, 22768 (2022)10.1364/OE.461378] cite previous prior works from the N. A. Riza lab that earlier reported a high speed lens based on digital polarization switching in cascade with birefringent fixed and tunable optical beamforming elements and its application for volumetric displays.

Editorial Introduction to the JSTQE Special Issue on Semiconductor Lasers

The papers in this special section focus on the topic of semiconductor lasers. Almost 60 years after their first demonstration this area of research remains one of the most active fields in photonics fueled both by the incorporation of new materials, structures and quantum effects as well as by the surge of novel applications that demand the unique properties of compactness, high-power, spectral richness and low linedwidth provided by these devices. These include communications, sensing, biophotonics and the more recent areas of lidar, optical beamforming, computing and quantum information systems. Each of them can leverage from the unique features of semiconductor lasers. The objective of this special section is to highlight recent progress, challenges and trends in innovative materials, geometries, modelling and applications of semiconductor lasers.