Optical Beamforming Network Research Articles

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.

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.

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.

Photonic Integrated Circuit for Optical Phase Control of 1 × 4 Terahertz Phased Arrays

In this manuscript, we report on a 1 × 4 optical beam forming network (OBFN) chip using optical phase shifters (OPSs) based on thermo-optically controlled optical ring resonators (ORRs) for 1D beam steering at 0.3 THz. The 1 × 4 OBFN chip consists of four OPSs and is fabricated using TriPleX technology. Each of the four OPSs is realized by two cascaded identical ORRs, to reach a phase shift of 2π. To allow transfer of the optical phase shift to the THz domain by optical heterodyning in high-frequency 1.55 µm modified uni-travelling carrier photodiodes, the ORRs are designed such that one carrier of the optical heterodyne signal is at the ORR’s resonance frequency, whereas the second optical heterodyne signal is at its off-resonance. By adjusting the resonance frequencies of the two ORRs in each OPS synchronously, a relative phase variation between two optical heterodyne carriers of up to 2π with a tuning efficiency of 0.058 W/π, is experimentally demonstrated. Due to the dispersive power transmission loss of the ORRs, phase tuning leads to a power variation of the optical heterodyne-generated signals up to 3.8 dB, which is experimentally characterized at 0.295 THz. It is shown numerically that this power variation only has a minor impact on the steering performance of a 1 × 4 phased array. The determined beam direction deviation and maximum absolute radiation power change are smaller than 1° and 2 dB, respectively. By sweeping the phase difference between two adjacent THz antennas in the 1 × 4 phased array, from −120° to 120°, a beam steering range of ~62° is demonstrated numerically at 0.295 THz.

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.

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%.

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.

Gain-enabled optical delay readout unit using CMOS-compatible avalanche photodetectors

A compact time delay unit is fundamental to integrated photonic circuits with applications in, for example, optical beam-forming networks, photonic equalization, and finite and infinite impulse response optical filtering. In this paper, we report a novel gain-enabled delay readout system using a tunable optical carrier, low-frequency RF signal and CMOS-compatible photodetectors, suitable for silicon photonic integration. The characterization method relies on direct phase measurement of an input RF signal and thereafter extraction of the delay profile. Both integrated silicon and germanium photodetectors coupled with low-bandwidth electronics are used to characterize a microring resonator-based, true-time delay unit under distinct ring–bus coupling formats. The detectors, used in both linear and avalanche mode, are shown to be successful as optical-to-electrical converters and RF amplifiers without introducing significant phase distortion. For a Si–Ge separate-absorption-charge-multiplication avalanche detector, an RF amplification of 10 dB is observed relative to a Ge PIN linear detector. An all-silicon defect-mediated avalanche photodetector is shown to have a 3 dB RF amplification compared to the same PIN detector. All ring delay measurement results are validated by full-wave simulation. Additionally, the impact of photodetector biasing and system linearity is analyzed.

Experimental Demonstration of Dynamic Optical Beamforming for Beyond 5G Spatially Multiplexed Fronthaul Networks

This paper presents a beyond 5G fronthaul network with dynamic beamforming and -steering. The proposed fronthaul solution deploys optical beamforming (OBF) by combining space division multiplexing (SDM), analogue radio-over-fiber (ARoF), and the novel optical beam forming network (OBFN) technologies. From the service management and orchestration (MANO) point of view, the proposed fronthaul solution also deploys an advanced software defined networking (SDN) and Network Function Virtualization (NFV) control and orchestration architecture developed with the goal to optimally manage and reconfigure the physical layer resources (i.e., optical and radio) at the central office and cell sites (i.e., pool of baseband units (BBUs), remote radio heads (RRHs), ARoF transceivers and OBFNs). The proposed beyond 5G fronthaul architecture is primarily oriented to deploy massive machine-type communication (mMTC) services with high-bandwidth requirements, such as for industry 4.0. In this paper we experimentally validate the novel OBFN system, and the dynamic SDN/NFV MANO of the transport connectivity and network services for optical beamforming. The obtained experimental results show that the overall delay for the provisioning and removal of an OBF service, considering the contribution of the involved optical and radio systems and the SDN/NFV MANO layer, is 134s and 18s respectively. The reconfiguration of the OBF service to add or remove a beam can be performed in the range of 65-87s.

Enhancing the directivity of a radiating array element for an optical true-time-delay network

The directivity of a horn antenna as a true-time-delay array element of an optical beam-forming network is enhanced by using a graded index dielectric lens. The proposed refractive index distribution of the lens is designed to mitigate the phase error at the antenna aperture while keeping the antenna reflectionless. Ray-tracing-based optimization is carried out to achieve the best design parameters and modify the horn’s body. Realization of the lens is also demonstrated by discretizing the refractive index of the lens into several layers. The half-power beamwidth value of an example horn antenna is divided by four using the proposed lens. The functionality of the proposed lens is verified by conducting ray-tracing and full-wave simulations using COMSOL.

True Time Delay Optical Beamforming Network Based on Hybrid Inp-Silicon Nitride Integration

We demonstrate a broadband and continuously tunable 1×4 optical beamforming network (OBFN), based on the hybrid integration of indium phosphide (InP) components in the silicon nitride (Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> ) platform. The photonic integrated circuit (PIC) comprises a hybrid InP-Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> external cavity laser, a pair of InP phase modulators, a Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> optical single-sideband full carrier (SSBFC) filter followed by four tunable optical true time delay lines (OTTDLs), and four InP photodetectors. Each OTTDL consists of eight cascaded thermo-optical micro-ring resonators (MRRs) that impose tunable true time delay on the propagating optical signals. The OBFN-PIC is designed to facilitate the steering of a microwave signal with carrier frequency up to 40 GHz over a continuous set of beam angles. We evaluate the performance of the OBFN-PIC to handle and process microwave signals, measuring the link gain, the noise figure (NF), and the spurious-free dynamic range (SFDR) parameters. Moreover, we assess its beamforming capabilities assuming that the OBFN-PIC is part of a wireless system operating in the downlink direction and feeds a multi-element antenna array. Using microwave signals at 5 and 10 GHz with quadrature amplitude modulation (QAM) formats at 500 Mbaud, we evaluate the performance of the OBFN-PIC under various configurations. We show that error-free performance can be achieved at both operating frequencies and for all the investigated beam angles ranging from 45° to 135°, thus validating its potential for high-quality beamforming performance.

Reflective coupled microring resonators for reconfigurable photonic systems: Performance analysis

We propose reflective type triple coupled microring resonators (TCMMRs) for reconfigurable photonic based systems. We have developed an analytical model and analyzed its useful performance characteristics. The TCMMRs based device exhibits a wide range of performance characteristics such as multi-band filtering, optical logical operations, and optical true-time delay lines. Reconfigurable multiple resonances and their splitting features associated with the device provide useful filtering performance characteristics such as high out-of-band rejection, flat-top bandwidth, and near to ideal shape factor. The device can perform multiple functions such as bandpass, bandstop, and notch filtering with a good performance. Unlike two input narrowband logical operations demonstrated in the literature, our proposed device can perform as three-input optical logical operator, and it can switch wideband microwave frequency signals optically. Moreover, the device exhibits wideband flat top group delay response. It carries out delay tuning using a single variable coupling coefficient which simplifies the complexity of the tuning encountered in binary tree-structured optical beamforming networks based on conventional microring resonators.

Chirped fiber grating and specialty fiber based multiwavelength optical beamforming network for 1X8 phased array antenna in S-band

In this paper, theoretical and experimental analysis has been done for the beam transmission of 2.2 GHz RF signal by 1X8 linear phased array antenna fabricated in S-band. The proposed architecture is based on true time delay optical beam forming network which gives squint free beam steering of RF signal. The optical beam forming network is based on chirp fiber Bragg grating (CFBG) and multiple lengths of highly dispersive specialty fiber element. Here, double sideband modulation technique of multiple wavelengths are adopted which explore the reflection property of CFBG with various chirp bandwidth. We measured the reflectivity and time delay response of CFBG, and dispersive fiber elements with theoretical analysis which is verified by experimental results. Theoretical and experimental measurements for the relative time delay was used to investigate the beam radiation pattern of 1X8 phased array antenna through simulation results. Wide range of beam steering ranges 3.5° to 18° have been achieved when specialty fiber of −100 ps/nm km dispersion coefficient was introduced.

Efficient 2D Optical Beamforming Network With Sub Partitioning Capability Based on Raised Cosine Chirped Fiber Grating and Mach-Zehnder Delay Interferometer

In this paper, a two-dimensional true time delay optical beamforming network (OBFN) has been proposed with sub partitioning capability for 3X3 phased array antenna (PAA) with operating frequency in X-Band. The architecture is based on raised cosine apodised chirp fiber Bragg grating (CFBG) and Mach-Zehnder delay interferometer (MZDI). Compared to unapodised CFBG, raised cosine apodization drastically reduces the ripple as well as sidelobes and gives a flat response in the passband of reflection spectrum. Multiwavelength optical signals with a wavelength difference of 0.3 nm are used to steer 10 GHz RF signal in elevation and azimuth direction. Further, broad angular control of beam radiation due to sub partitioned PAA is also demonstrated. The RF signal beam is steered in elevation at -62.2,-31.9, and-10.8 degrees, and in azimuth at 123.6 and 55.9 degrees. Theoretical analysis of the OBFN has been presented and validated with the experimental results. At the best of our knowledge, delay characteristics of raised cosine apodised CFBG have been theoretically explored for the first time with mathematical formulation and a comparative discussion is given with the measured data.

All‐fibre phase shifter based on tapered fibre coated with MoWS 2 ‐rGO

In this work, an all-fibre phase shifter using tapered fibre coated with molybdenum tungsten disulfide - reduced graphene oxide (MoWS2-rGO) is demonstrated. The large evanescent field of tapered fibre allows MoWS2-rGO to absorb injected light from a 1400-nm pump. It subsequently modifies the refractive index of both an MoWS2-rGO solution and tapered fibre because of the thermo-optic effect. A maximum wavelength shift of 2.489 nm is observed and the equivalent phase shift is 0.91π. The efficiency of the phase shifter is calculated at 0.0175 nm/mW. The proposed phase shifter is beneficial for a variety of applications, specifically for future optical beam-forming networks and all optical signal processing devices.

An integrated optical beamforming network for two-dimensional phased array radar

In recent years, optically controlled phased array radar has been widely used because of its high radiation power, flexible beam steering and anti-electromagnetic interference, but the radar system based on discrete devices is still plagued by the problems of large size, high power consumption and complex control method. In this paper, we propose a two-dimensional integrated optical true time delay network (OTTDN), which has the abilities of real-time monitoring and adjustment. The delay network is implemented with silicon-based adjustable optical delay chip. The chip contains four-channel delay lines with different steps to achieve more compact volume, which can realize 128 × 4 kinds of delay amount, but the size is only 5.7 × 15.8 mm2 and the power consumption of all chip is 4.32 W. The results of delay chip measurement show that the maximum delay mean error is -0.55 ps, and the maximum root mean square error (RMSE) is 0.80 ps in four-channel. Based on these delay results, the pointing error of array antenna is less than 0.5° in the frequency of 3 GHz. If a power division structure is added to the RF front-end, this network can also be used in multi-beam systems, whose beams can be controlled independently at the same time.

A wideband 1[formula omitted]4 optical beam-forming chip based on switchable optical delay lines for Ka-band phased array

Comparing with electronic beam forming, integrated optical beam forming is very promising for optical controlled phase array system, because much broader band beam steering can be achieved without the beam squint effect. The single channel optical true time delay lines based on the cascade microring resonators and switched optical delay waveguides have been extensively investigated. The optical beam forming chip based on multi-channel microring resonators have also been demonstrated, however only limited working bandwidth were obtained due to their inherent tradeoff between the delay and bandwidth. The bandwidth limitation can be overcome by using integrated optical beam forming chip composed of switched optical delay waveguides, which has not been demonstrated and evaluated. Here, a 1×4 optical beamforming chip with four integrated switchable delay lines units designed to control the Ka-band phased antenna arrays is proposed and demonstrated experimentally. The maximum delay of 96 ps with a delay increment about 3.02 ps/stage was obtained, which is in accordance with the design well. Based on the measured delay times, the directional diagrams of the optical beamforming network were simulated and beam angle coverage of 90° can be achieved. Furthermore, a magnitude response experiment was carried out to evaluate the performance of the optical beam forming chip, and a remarkable working bandwidth of 29 GHz was achieved.

Microwave Photonic Array Radars

Phased array radars have remarkable advantages over radars with single-element antenna in terms of agility, flexibility, robustness, and reconfigurability. Current pure-electronic phased array radars face challenges when operating with a large frequency tunable range and/or with broad instantaneous bandwidth. Microwave photonics, which allows wide bandwidth, flat frequency response, low transmission loss, and immunity to electromagnetic interference, is a promising solution to cope with issues faced by pure electronics. In this paper, we introduce a general architecture of microwave photonic array radar systems and review the recent advancement of optical beamforming networks. The key elements for modelling the response of the true time delay (TTD) and/or phase-shifting unit are presented and discussed. Two typical array antenna structures are introduced, i.e., microwave photonic phase shifter based array and optical true time delay based array, of which the principle and typical implementations are described. High-resolution inverse synthetic aperture radar (ISAR) imaging is also realized based on a microwave photonic array radar. The possibility of on-chip integration of the microwave photonic array radar is discussed.

Dispersion-tailored few-mode fiber design for tunable microwave photonic signal processing.

We present a novel double-clad step-index few-mode fiber that operates as a five-sampled tunable true-time delay line. The unique feature of this design lies in its particular modal chromatic dispersion behavior, which varies in constant incremental steps among adjacent groups of modes. This property, which to the best of our knowledge has not been reported in any other few-mode fiber to date, is the key to tunable operation of radiofrequency signal processing functionalities implemented in few-mode fibers. The performance of the designed true-time delay line is theoretically evaluated for two different microwave photonics applications, namely tunable signal filtering and optical beamforming networks for phased array antennas. In the 35-nm optical wavelength tuning range of the C-band, the free spectral range of the microwave filter and the beam-pointing angle in the phased array antenna can be continuously tuned from 12.4 up to 57 GHz and 12.6° up to 90°, respectively.

Silicon integrated microwave photonic beamformer

Optical beam-forming networks (OBFNs) based on optical true-time delay lines (OTTDLs) are well known as the promising candidate for solving the bandwidth limitation of traditional electronic phased array antennas (PAAs) due to beam squinting. Here we report, to the best of our knowledge, the first monolithic 1 × 8 microwave photonic beamformer, based on switchable OTTDLs on the silicon-on-insulator platform. The chip consists of a modulator, an eight-channel OBFN, and eight photodetectors, thus including hundreds of active and passive components in total. It has a wide operating bandwidth from 8 to 18 GHz, which is almost two orders larger than that of electronic PAAs. The beam can be steered to 31 distinguishable angles in the range from − 75.51 ∘ to 75.64°, based on the beam pattern calculation with the measured radiofrequency response. The response time for beam steering is 56 µs. These results represent a significant step toward the realization of integrated microwave photonic beamformers that can satisfy compact-size and low-power consumption requirements for the future radar and wireless communication systems.