Search

The on-chip optical power splitter is a common and important device in photonic integrated circuits (PICs). To achieve a low insertion loss and high uniformity while splitting the guided light, multi-mode interferometer-based structures utilizing a self-imaging principle are widely used mainly in the form of a 1 × 2 configuration. Recently, an inverse design method for nanophotonic devices has emerged to overcome the limited capability of the conventional design methods and make it possible to explore the vast number of design parameters. Because of the non-intuitive shape of inverse-designed structures, they allow us to discover interesting and complex optical responses which are almost impossible to find with conventional design methods. Here, we report two kinds of inverse-designed 1 × 4 optical power splitters composed of silicon bars of different lengths, which are fabricated with a standard CMOS-compatible process. The particle swarm optimization method was used to minimize the insertion loss and divide the power evenly into each output port with finite-difference time-domain method simulation. The first optical power splitter has a compact size of 8.14 × 12 μm2 and the second optical power splitter has an even more compact size of 6.0 × 7.2 μm2. With the inverse designed structures, we fabricated the chip with a CMOS-compatible fabrication process. Experimental verification of the structures is provided and good agreement with the numerical results is obtained. The first 1 × 4 optical power splitter has a low insertion loss of less than 0.76 dB and uniformity of less than 0.84 dB, and the second more compact optical power splitter has a low insertion loss of less than 1.08 dB and uniformity of less than 0.81 dB. As the complexity of on-chip photonic systems has steadily increased, the inverse design of photonic structures holds great potential to be an essential part of advanced design tools.

We demonstrate beam steering using a passive silica optical phased array (OPA) with wavelength tuning. In this OPA, a constant path difference is built up to assign sequential phase delays with a wavelength variation in arrayed waveguide channels for the beam steering. From as-fabricated 1 × 101 passive silica OPA chips, we successfully achieved beam forming with a transversal divergence angle of 0.57° at a 1548.3-nm wavelength and also beam steering of 15.4° by wavelength tuning of 30.7 nm. Combining a cylindrical lens in front of the end-fire radiators, the longitudinal divergence angle could be reduced from 13.0° to 0.42°. The side-mode suppression ratio of the beam was 10.3 dB at the center position. Through simulation, we analyzed the effects of the phase errors on the beam quality, due to the effective index fluctuation of the waveguide channels, and provided an allowable error range to attain beam forming from the passive OPA.

Efficient extraction of light from a high refractive index silicon waveguide out of a chip is difficult to achieve. An inverse design approach was employed using the particle swarm optimization method to attain a vertical emitting meta-grating coupler with high coupling efficiency in a 220-nm-thick silicon-on-insulator platform. By carefully selecting the figure of merit and appropriately defining parameter space, unique L-shape and U-shape grating elements that boosted the out-of-plane radiation of light were obtained. In addition, a 65.7% (−1.82 dB) outcoupling efficiency and a 60.2% (−2.2 dB) fiber-to-chip vertical coupling efficiency with an 88 nm 3 dB bandwidth were demonstrated by numerical simulation. Considering fabrication constraints, the optimized complex meta-grating coupler was modified to correspond to two etching steps and was then fabricated with a complementary metal-oxide-semiconductor-compatible process. The modified meta-grating coupler exhibited a simulated coupling efficiency of 57.5% (−2.4 dB) with a 74 nm 3-dB bandwidth in the C-band and an experimentally measured coupling efficiency of 38% (−4.2 dB).

We demonstrate optical wireless transmission with two-dimensional (2D) beam-steering using an optical phased array (OPA). The OPA consists of 64-elements of electro-optic p-i-n phase shifters and thermo-optic tunable n-i-n grating radiators, employed for 2D beam-steering in the transversal and longitudinal directions. The design of the transmitter and receiver device parameters allowed the error-free transmission of 32 Gbps data over a distance of 3 m. The beam-steering range covered 46.0°/10.2° in the transversal/longitudinal direction with a beam divergence of 0.7°/0.9°. When compared with a transmission over fiber, it was confirmed that free-space transmission through the OPA did not degrade the quality of the tens of Gbps signals.

We developed an inter-chip optical link using direct optical wire (DOW) bonding by open-to-air polymerization. An arch-shaped wire was drawn from a tip in a similar way to a metal wire, but the wire was formed from a polymer solution that solidified in the air during wiring. The DOW bonding was examined for silicon photonic chips where grating couplers are integrated for input/output coupling. Cone-shaped studs were formed at the ends of the wire, and their geometry was optimized using finite-difference time-domain simulation to give a mode conversion function. Although the polymer wire had a multimode scale of 7 µm, the wire bonding between the grating couplers showed a relatively low insertion loss of 5.8 dB at a wavelength of 1590 nm compared to a conventional connection using single-mode fiber blocks. It also showed a larger wavelength tolerance within the range of ∼1520–1590 nm. DOW bonding between a grating coupler and a single-mode fiber were also examined to verify the feasibility of out-of-plane connection with edge-coupling devices. The grating-to-fiber wire link also exhibited a large wavelength tolerance.

Precise imaging in three-dimension (3D) is an essential technique for solid-state light detection and ranging (LiDAR). Among various solid-state LiDAR technologies, silicon (Si) optical phased array (OPA)-based LiDAR has the significant advantage of robust 3D imaging due to its high scanning speed, low power consumption, and compactness. Numerous techniques employing a Si OPA have utilized two-dimensional arrays or wavelength tuning for longitudinal scanning but the operation of those systems is restricted by additional requirements. Here, we demonstrate high-accuracy 3D imaging using a Si OPA with a tunable radiator. As we adapted a time-of-flight approach for distance measurement, we have developed an optical pulse modulator that allows a ranging accuracy of less than 2 cm. The implemented Si OPA is composed of an input grating coupler, multimode interferometers, electro-optic p-i-n phase shifters, and thermo-optic n-i-n tunable radiators. With this system, it is possible to attain a wide beam steering range of 45° in a transversal angle with a 0.7° divergence angle, and 10° in a longitudinal angle with a 0.6° divergence angle can be achieved using Si OPA. The character toy model was successfully imaged in three dimensions with a range resolution of 2 cm using the Si OPA. The further improvement of each component of the Si OPA will allow even more accurate 3D imaging over a longer distance.

We proposed inverse-designed nanophotonic waveguide devices which have the desired optical responses in the wide band of 1450-1650 nm. The proposed devices have an ultra-compact size of just 1.5 µm × 3.0 µm and are designed on a silicon-on-insulator (SOI) waveguide platform. Individual nano-pixels with dimensions of 150 nm × 150 nm were made of either silicon or silicon dioxide, and the materials for the 200 total cells were determined using a trained deep neural network. While training the two networks, the hyperparameter optimization method was applied to make the training process efficient. We then fabricated the proposed devices using a CMOS-compatible fabrication process, and experimentally verified the fabricated device performance.

The authors demonstrate integrated 1D optical phased arrays (OPAs) for wide-angle 2D beam-steering. The 2D OPA consists of 16 1D transversal steering OPAs whose radiators have different grating periods, to assign different longitudinal angles. The transversal steering of each OPA is performed by the phase control of the p-i-n electro-optic phase shifter array. The 1D transversal steering OPAs operate serially, changing the longitudinal radiation angle. The grating radiators were designed with an array pitch of 2 μm, and a varying period in the range of 610-710 nm. The entire 16 × (1 × 16) OPAs were integrated into a small area of 26.5 mm 2 . The obtained transversal/longitudinal beam-steering range was 46°/44°, respectively, with a wavelength of 1560 nm, which enables wide 2D beam-steering.

The authors demonstrate the collimation of a vertically diverged beam emitted from a silicon-based end-fire optical phased array (OPA) using an aspheric cylindrical lens. A micro-cylindrical lens with a numerical aperture of 0.8 was placed near the focal length in front of an 1 × 16 end-fire OPA with a half-wavelength (775 nm) radiator array pitch for a 1550 nm wavelength. The lens provided a great collimation effect, reducing the vertical divergence angle from 95.6° to 6.7° during horizontal beam steering over ±30°. The horizontal divergence angle showed some expansion, from 7.6° to 10°, due to the angle-dependant curvature of the lens and the distance to the lens surface.

We present a $1\times 16$ silicon optical phased array using electro-optic phase shifters to attain high-speed operation with low power consumption. The phase shifters are constructed using a $p$ - $i$ - $n$ junction structure with the $p$ - and $n$ -doped regions formed on both sides of the $i$ -region. The $i$ -region width of the phase shifter is optimized considering the power consumption for phase-tuning and the propagation loss in the phase shifter. The fabricated $p$ - $i$ - $n$ phase shifter exhibits a fast operating speed of 20 MHz and a low phase-tuning power of 1.7 mW/ $\pi $ . From a 1-D optical phased array integrated with 2- $\mu \text{m}$ -pitch grating radiators, a wide beam-steering range of 45° is attained along the transversal direction at a $1.55~\mu \text{m}$ wavelength. Average power consumption for the beam-forming operation of the $1\times 16$ OPA is measured to be 39.6 mW and the average transition time to steer the beam is 24 ns.

Using the knowledge that any gate can be built through different arrangements of micro-ring resonators, this paper proposes the all-optical design of XOR and XNOR logic gates. The gates structure thus consists of micro-ring resonators (MRR) paired with a constant source of light (COS). MRRs in these designs are utilized as modulators by tuning their resonant wavelengths. In this way, under no external disturbances, the rings are uncoupled by default. The proposed devices are CMOS-compatible meaning that they can be fabricated using the existing technologies. Also, to reduce the fabrication complexity of the proposed devices, thermo-optic modulation is employed as primary light modulating technique. The logic gates are tested at 25 kpbs. Device parameters are provided as well for manufacturing purposes. The study concludes with suggestions on design improvements and potential application of the optical gates.

In this paper, an integrated optical receiver module with demultiplexer chip-to-chip optical interconnects is proposed. The receiver and demultiplexer (demux) were realized on a single chip in a 0.18 μm TSMC CMOS technology. The topology uses a 1:2 for the demux while the receiver (Rx) module consists of transimpedance amplifier (TIA) and a limiting amplifier (LA). The receiver achieved a gain of 90 dBΩ and a 3-dB bandwidth of 4.5 GHz. Clear eye diagrams were observed with a voltage swing of 375 mVpp up to 2.5 Gbps output from the Rx-Demux at 5 Gbps input signal. The integrated chip occupies an area of 594x1089 μm2 with power consumptions of 122 mA under a 1.8 V power supply This solution could be applied to CPU/memory interface where bidirectional signaling is required.

We present an 1x16 silicon optical phased array (OPA) based on an electro-optic phase shifter that enables low power consumption and high speed operation. The phase shifter operates by carrier injection based on the p-i-n structure and is designed to optimize the width between doped regions to 2.5 μm. Phase tuning efficiency of 1.7 mW/π and operating speed of 20 MHz were measured from fabricated devices. The difference between the measured values and the values calculated in the simulation was analyzed through additional simulations to indicate that the error occurred in the actual fabrication. In addition, transversal beam steering was achieved in the range of 45° and the average power of 39.6 mW was consumed for phase tuning for each radiation beam.

Optical wireless data transmission is an emerging complementary technology compared to the RF transmission in 5G and 6G communications. The optical phased array (OPA) would be a promising component for such high-speed wireless transmission requiring beam-steering function. We achieved 25Gbps data transmission using silicon-based OPA and commercialized photodetector (PD). OPA was designed as 64 channels having output beam divergence angle less than 1 for both horizontal and vertical direction. The diverging beam is received by high-speed PD with active diameter less than 30μm. The demonstration of 20Gbps data transmission was practiced with OPA’s output beam power as 0dBm and a freespace range of 1.5m. Received signal from photodetector has an eye-diagram with an extinction ratio of 5dB. Depending on our link power budget, higher output beam power and smaller beam divergence angle concludes to longer free-space range and larger bandwidth. Improvements on beam concentration by lens system could also increase range and bandwidth.

In this work, we investigate an optical accelerometer utilizing single-mode Si/SiO2 waveguides at 1550 nm as a displacement sensing unit. The device is based on quad beam configuration, made of a fixed frame and a mass, moving within a limited range along vertical direction. Three straight Si/SiO2 waveguides are placed aligned along the central axes of the accelerometer, two on both ends on the frame and one on the mass, such that the displacement of mass leads to a drop of the coupled light intensity. When the mass is at rest, the intensity of the guided mode is at its highest value. Acceleration is then measured by monitoring the intensity modulation. Lateral dimensions of the waveguides are similar, where the height and width are 200 nm and 500 nm, respectively. The effective index of single mode Si/SiO2 waveguides (neff = 2.3550 at 1550 nm) is calculated using Finite Difference Eigenmode (FDE) method. The field profile of fundamental TE mode is to a good approximation given by Gaussian field distribution. The correlation of guided light intensity and the mass displacement was obtained numerically using mode-coupling theory. We show that our configuration is highly sensitive, drastic intensity drop (100 dB) happens at mass-frame misalignment within ±7 μm and displacement by 3 μm causes intensity decrease of 10.8 dB. Thus, design of CMOS-compatible miniature silicon photonic accelerometers with inherent properties such as multiplexability and immunity to external electro-magnetic fields are promising candidates for low cost real-time vibration monitoring sensors applicable in harsh environments.

In this work, we design a Si-based Fresnel-zone lens for a hybrid 3D integrated circuit (3D IC) solution. The 3D IC solution consists of two layers of transceiver modules which are mounted at several points on an optical printed circuit board (OPCB) for seamless transmission of signal through each layer to the OPCB and vice versa. Each transceiver module is made up of a Si-subcarrier (Si layer), transceiver IC, laser diode (VCSEL) and photodiode (PD). The transceiver IC, LD and PD are flip-chip bonded to the Si-subcarrier. Fresnel-zone lens are designed on the transmission surface of each of the Si-subcarriers to improve coupling efficiency, transmittance through the silicon substrate, reduce surface scattering, and improve focusing. Each of the Si-subcarrier with the transceiver modules are flip-chip bonded together and also flip-chip bonded to the optical PCB. A 2-level and 4-level Fresnel-zone lens are designed at 1.3μm and 1.55μm. Based on design parameters such as coupling efficiency, transmittance, less design complexity, and ease of fabrication, the 4-level Fresnel zone lens was selected as the optimal design for 3D IC and optical PCB applications. The optimal 4-level Fresnel-zone lens are designed for λ=1.3μm, where the focal length, f is 350μm, and diameter, D, is 167μm; and for λ=1.55μm, where the focal length, f is 350μm, and diameter, D, is 169.2μm. Also the plots of coupling efficiency and transmittance are provided for applications in 3D IC optical interconnects.

We describe the design, development, and performance of a complementary metal-oxide semiconductor (CMOS) image sensor read-out circuit. Designed in a 0.35-m CMOS technology and occupying an area of 2.3 13.6mm2, the proposed multipixel image sensor readout integrated circuit with internal timing generator achieves high performance with 188.7-V root mean square (RMS) of ultralow output noise, wide linear dynamic range of 2.3V, low power consumption of 42mA, and a simple timing scheme. The approaches to boost linear dynamic range are presented. The image sensor also provides the trigger signal for data acquisition purpose.

We demonstrate a compact and high-performance $1\times 2$ silicon MMI switch by thermo-optic control of symmetric interference modes using local and direct heating of the mode-peak regions. The direct heater is formed with n-i-n-i-n resistors whose $i$ -regions are placed at the peak regions of the first two-folded image. Three electrodes are separately formed on each $n$ -doped region for alternative heating of the two $i$ -regions. Using a symmetric $1\times 2$ MMI designed as a 50:50 splitter under no bias, path switching is attained by inducing a phase difference of ± $\pi$ /2 between the two modes, applying a bias to either n-i-n heater. From this switching scheme, we achieve a low crosstalk of less than −30 dB with a compact active area of 3 $\mu \text{m}\times40~\mu \text{m}$ . We also observe a fast switching response with a rising time of $1.04~\mu \text{s}$ and a falling time of $0.89~\mu \text{s}$ .

Optical wireless data transmission is an emerging complementary technology compared to the radio frequency transmission. Due to the characteristics of optical radiation, optical wireless transmission has high-speed data transmission, unlimited bandwidth, high security and immune to signal interference. Despite from most self-alignment optical wireless systems such as MEMS, optical phased array (OPA) has a large advantage on the entire system size, low power consumption and high speed operation. The manufactured OPA has 16 channels, achieving ±22.7° beam steering angle. Radiator's output beam has a beam divergence angle of 4° and 6° for each horizontal and vertical direction. By using the OPA, we have demonstrated a 5Gbps data transmission in free space. By phase tuning, data transmission can shift from center positioned photodetector to another photodetector at fully steered beam position. The extinction ratio of the transmission eye-diagram was over than 7dB. These results show that OPA is a promising technology for high-speed optical wireless communication with self-alignment function.

This paper focuses on design of specific type of optical logic gates - universal gates (NAND and NOR). These gates are based on microring resonators (MRR) coupled both in series (for NAND gate) and in parallel (in case of NOR gate). Because of their simplicity in terms of fabrication, the MRRs are modulated through thermo-optic effect of silicon. The MRRs in the proposed devices act as input ports combined with a constant source of light at specific wavelengths. Thus, through different coupling configurations of the rings, the logic is obtained. Due to the architectural features of the devices, complements of these gates (AND, OR) can be obtained as well. Consequently, the proposed designs exhibit the behavior of universal gates and their complements simultaneously. In addition, using Optical Spectrum Analyzer (OSA) as well as Optical Oscilloscope, static and corresponding dynamic responses are illustrated. Furthermore, complementary parameters such as extinction ratio and speed are evaluated.

An optical system which consists of a transmitter array, a fiber array, and a receiver array, experience some signal loss and crosstalk as the signals travel from the transmitter to the receiver. Signal loss and crosstalk occur at the interface between the light source (Vertical Cavity Surface Emitting Laser, or the VCSEL) and the fiber array, and also at the interface between the fiber array and the detector (photodetector). In order to obtain the real-time analysis of the transmitted and crosstalk signals, optical convolution is employed in this work. Optical convolution of the radiated signals (from the VCSEL) and the fiber array is performed to determine the signal intensity at the receiver end and also the amount of crosstalk in the array system. Transmitted signal intensity and crosstalk are essential for defining signal integrity and reliability during the packaging of optoelectronic transmitter and receiver modules in an optical system. A theoretical analysis of transmitted and crosstalk signals is performed with various separation distances between the transmitter modules and the fiber array and with a zero separation distance between the fiber array and the photodetector. The analysis is also performed for a top-emitting VCSEL (for the planar transmitter module) and bottom-emitting VCSEL (for the multi-chip transmitter module). The optical convolution allows us to obtain the real-time and the actual transmitted and crosstalk signals at the receiver end of an optical array system. It also provides optical system performance analysis.

Optical wireless data transmission is an emerging complementary technology compared to the radio frequency transmission in specific fields. Silicon based solid-state optical phased array (OPA) has a large advantage on the entire system size, low power consumption and high speed operation. The designed radiator of OPA has 16 channels of grating array with each grating having 20μm length and etch depth of 70nm. Grating array radiator has 2μm pitch achieving ±22.7° beam steering angle. Radiator’s output beam has a beam divergence angle of 4° and 6° for each longitudinal and vertical direction. With the designed OPA, we have demonstrated a 5Gbps data transmission in a free-space range of 30cm. Eye diagram was achieved at center and full steered beam position by phase shifting. The extinction ratio of the transmitted eye-diagram was about 7dB verifying that OPA is a promising technology for high-speed wireless data transmission.

We demonstrate the on-chip monitoring of far-field patterns in a silicon-based optical phased array (OPA) using a planar diffractor and traveling-wave photodetectors (PDs) integrated at the end of the radiator array. To reproduce the diffraction patterns within a silicon slab, the planar diffractor is designed with a diffraction region surrounded by an absorptive boundary and seven discrete outlet waveguides. Each outlet waveguide is linked to the photon-assisted tunneling PD which has a silicon p - n junction and is operated under a reverse bias to detect a sub-bandgap wavelength, 1.3 µm. With the 1 × 16 OPA and seven detectors, the positions of the main beams aligned to specific directions in the free space were clearly monitored.

We demonstrate wide-angle beam-steering using an optical phased array (OPA) with waveguide radiators designed with non-uniform widths to reduce the crosstalk between waveguides. The OPA consists of a silicon based 1 × 16 array of electro-optic phase shifters and end-fire radiators. The 16 radiators were configured with four different widths and a half-wavelength spacing, which can remove the higher-order diffraction patterns in free space. The waveguides showed a low crosstalk of −10.2 dB at a wavelength of 1540 nm. With phase control, the OPA achieved wide beam-steering of over ±80° with a side-lobe suppression of 7.4 dB.

Optical phased array (OPA) is considered as promising device in LiDAR application. We implemented a 1x16 silicon OPA consisting of an array of p-i-n electro-optic phase shifters and thermo-optic tunable grating radiators capable of two-dimensional beam-steering. The OPA was fabricated with CMOS-compatible process using SOI wafer. The p-i-n electro-optic phase shifters were formed in OPA channels for transversal beam-steering. With an array pitch of 2 μm, we attained transversal steering up to 45.6° at 1550 nm wavelength. For longitudinal beam-steering, we employed thermo-optic tunable grating radiators with p-i-n junction. The i-region covers whole radiator array and the p- and n-doped regions are placed on the both sides of the radiator array. This structure can provide fairly uniform heating of the radiator region, shifting the overall radiation field in longitudinal direction by the thermo-optic effect. As a result, a longitudinal beam-steering up to 10.3° was achieved by forward-biasing with a power consumption of 178 mW. This result proves a possibility of wide two-dimensional beam-steering with one-dimensional OPA without using tunable light source. We confirmed that the longitudinal tuning range obtained above is corresponding to near 100 nm wavelength tuning. Our device scheme can be a cost-effective solution of the OPA and also be a solution of self-adjustment for fluctuation of the wavelength-dependent performances.

We demonstrate a tunable grating coupler for broadband operation using an impurity-doped thermo-optic heater fabricated by complementary metal–oxide–semiconductor-compatible processes. As a thermo-optic heater, a p-n diode is employed to have a p-type region inside of an in-coupling grating connected with outside p+/n+ contacts and is heated directly by a current flow through the grating. Applying a forward-bias voltage of 7 V, we shift the central wavelength of the grating coupler from 1525 to 1574 nm with a coupling efficiency of close to −4 dB. Considering a 1-dB bandwidth at each central wavelength, we extend the operational bandwidth to nearly 90 nm. A thermal tuning efficiency of 0.23 nm/mW and transient responses of 32/ $22~\mu \text{s}$ for heating/cooling times are obtained.

In this paper, a transimpedance amplifier (TIA)-optical receiver (Rx) using two intersecting active feedback system with regulated-cascode input stage has been designed and fabricated for optical interconnects. The optical TIA-Rx chip is designed with 130 nm CMOS technology and operates up to 10 Gb/s data rate. The TIA-Rx chip core occupies an area of $$0.051\, \hbox {mm}^{2}$$0.051mm2 with power consumption of 16.9 mW at 1.3 V. The measured input-referred noise of optical TIA-Rx is $$20\hbox {pA}/\surd \hbox {Hz}$$20pA/?Hz with a 3-dB bandwidth of 6.9 GHz. The proposed TIA-Rx achieved a high gain-bandwidth product per DC power figure of merit of $$408 \,\hbox {GHz}\Omega /\hbox {mW}$$408GHzΩ/mW.

This paper presents thermal analysis on crosstalk and performance of optoelectronic transmitter modules and also demonstrates the thermal analysis for efficient heat dissipation for the transmitter modules. The thermal crosstalk model for analysis is based on interconnects parameters for vertically stacked and horizontally packaged optoelectronic transmitter modules. While the analytical expression is used to estimate the thermal critical frequency, f crit_th , above which signals become severely deteriorated, a Teflon-based thermal printed circuit board (PCB) has been designed for packaging the optoelectronic transmitter modules to ensure efficient heat dissipation. The thermal and performance analysis of the packaged modules show that the chips operate at temperatures below the f crit_th , which is apt for reliable data and signal transmission.

This work presents a full-duplex and multifunction bidirectional transceiver for optical interconnect application. The transceiver utilizes a common limiting amplifier/gain stage, thus reducing total chip area and total power consumption. While providing a full-duplex bidirectional transmission with the aid of a hybrid circuit between the electrical input/output (I/O) and the optoelectronic signals from the transmitter and receiver circuits, it also allows for a half-duplex operation with the aid of a switch between the transimpedance amplifier signals and the transmitter electrical input from the I/O port. The multifunction bidirectional CMOS transceiver is designed in a 0.13 µm Si-CMOS technology, with power dissipation of 79 and 54.4 mW for the transmitter and receiver, respectively. It shows a 3-dB bandwidth of 5.58 and 5.69 GHz for the transmitter and the receiver respectively and with a 3-dB gain of 66.14 and 69.6 dB, in full-duplex mode. The transceiver operates up to 7 Gb/s in full-duplex mode.