Dual-drive Mach-Zehnder Modulator Research Articles

Photonic architecture for remote multi-parameter measurement and transmission of microwave signals

Photonic architecture for remote multi-parameter measurement and transmission of microwave signals

Microwave Photonics Broadband Doppler Velocity Simulator with High Spurious Suppression Ratio by Using Serrodyne Modulation

A Doppler velocity simulation method based on serrodyne modulation is proposed to achieve the frequency shift from hundred hertz to megahertz. One sub-phase modulation (PM) in a dual-parallel dual-drive Mach–Zehnder modulator loads a sawtooth signal to achieve a small frequency shift of the optical carrier. The other three sub-PMs implement carrier-suppressed double-band modulation of the RF signal. The RF signal is directly coupled from the receiving antenna to the modulator’s RF port without any electrical devices like a 90° hybrid, which ensures a broad operational bandwidth of the system. After filtering out one of the RF modulation sidebands by an optical filter, Doppler frequency shifting (DFS) is realized through frequency beating. The half-wave voltage of modulators rapidly decreases at low frequency shifts, leading to an increase in spurious signals. In order to improve the spurious suppression ratio (SSR) of DFS, a digital pre-distortion compensation based on the measured half-wave voltage is implemented in the frequency domain. Experimental results show that SSRs are larger than 35 dB when frequency shifts range from 0.1 kHz to 1 MHz. The RF operation bandwidth covers 2–40 GHz. The effectiveness of a Doppler velocity simulator is evaluated, and the simulation velocity error is less than 0.06 km/h. The proposed method has potential applications in both broadband electronic warfare and traffic metering applications.

Harmonic active mode-locking optoelectronic oscillator with suppressed supermode noise based on pulse intensity feedback.

A harmonic active mode-locking optoelectronic oscillator (HAML-OEO) with pulse intensity feedback is proposed and experimentally demonstrated. It is capable of generating microwave pulses characterized by suppressed supermode noise, uniform intensity, and tunable repetition rates. Unlike traditional HAML-OEOs, active mode-locking and pulse intensity feedback are simultaneously achieved through the use of a dual-drive Mach-Zehnder modulator (DDMZM). By synchronously feeding back the generated microwave pulses to the DDMZM, each pulse undergoes a loss proportional to its intensity, facilitating pulse intensity equalization and supermode noise suppression. In the experiment, intensity-equalized microwave pulse trains with repetition rates of 499 kHz and 998 kHz are generated by the 5th- and 10th-order HAML-OEOs, respectively, with the measured supermode noise suppression ratios exceeding 40 dB.

Photonic Measurement for Doppler Frequency Shift and Angle of Arrival Based on Integrated Dual-Parallel Dual-Drive Modulator

A microwave photonic Doppler frequency shift (DFS) and angle of arrival (AOA) measurement method based on a dual-parallel dual-drive Mach–Zehnder modulator (DP-DDMZM) is proposed and demonstrated. A sawtooth wave signal is used to drive the DC port of the modulator to realize the optical frequency shift, and thus the direction discrimination of DFS is realized. Due to single-sideband modulation, the proposed system can avoid periodic power fading and the separation of the remote antenna unit (RAU) and central office (CO) can be achieved. In the experiment, the microwave DFS is estimated with a clear direction and a maximum measurement error of 0.25 Hz over an ultrawide operation frequency from 6 to 36 GHz. The experiment also proves that the phase error of AOA measurement is less than 1.5 degrees. Compared with the traditional electronic microwave measurement scheme, the proposed scheme has great competitive advantages in future broadband electronic applications due to the features of multifunction, large bandwidth and anti-interference.

Full-duplex multi-band 5G/6G coexistence mobile fronthaul network based on RoF with RF self-interference cancellation

A bidirectional multi-band mobile fronthaul network based on the radio over fiber technology is proposed, which allows three different radio frequency (RF) bands at 3.5 GHz, 26 GHz, and 60 GHz full-duplex transmission, and 2.1 GHz RF band transmission as supplementary uplink, aiming for fifth-generation (5G)/sixth-generation (6G) mobile communication coexistence. The proposed scheme uses a dual-drive Mach-Zehnder modulator and dual-polarization binary phase-shift keying modulator to alleviate the interference between multiple RF bands. The transmission performance of the proposed system is evaluated by the simulation. The error vector magnitude of the system conforms to the 3GPP specification when the received optical powers of downlink and uplink are above −2.2 and −4.6 dBm, respectively. The Y-polarized optical carrier in the downlink is reused as the carrier of the uplink signals. Besides, a dual-parallel Mach-Zehnder modulator is used to realize RF self-interference cancellation at 60 GHz RF band in the uplink of the in-band full-duplex transmission. The cancellation depth of 27.08 dB is achieved by the proof-of-concept simulation.

Microwave photonic multi-frequency reconfigurable PSK/ASK/FSK formats modulation signals generation

We report a novel photonic approach to generate reconfigurable multi-frequency multiple binary modulation formats microwave signals based on a dual-polarization dual-drive Mach-Zehnder modulator (DPol-DDMZM). Two radio frequency (RF) signals and two electrical coding signals are applied to the modulator. By simply setting the proper formats of the applied coding signals, multi-frequency phase shift keying (PSK), amplitude shift keying (ASK) and frequency shift keying (FSK) microwave signals can be generated successfully. Our proposed scheme has been theoretically analyzed and experimentally demonstrated. The tunability of the bit rates and center frequencies of the system has been also proved. No polarization controller (PC) or polarizer (Pol.) is involved, resulting in the independent polarization of the system. Compared with previous reports of single-frequency PSK/ASK/FSK format microwave signals generation system, our proposed simple and compact system realizes multi-frequency reconfigurable functions without the necessity of changing system structure, which can bring great potential application in the multi-frequency radar and communication systems.

Photonic angle-of-arrival measurement of microwave signals using a triangular wave.

A novel, to the best of our knowledge, photonics-assisted approach for measuring the angle-of-arrival (AOA) of microwave signals with a large measurement range is proposed. The system utilizes a dual-drive Mach-Zehnder modulator (DDMZM) for signal modulation, followed by an optical filter for sideband selection. The dc port of the DDMZM is fed by a triangular wave to generate a pair of opposite frequency shifts. An intermediate frequency (IF) signal with a periodic phase jump is obtained after photodetection. The AOA of the incoming signals can be estimated by measuring the value of the phase jump. The key novelty of the proposed scheme lies in the application of a triangular wave to shift the frequency of optical signals, which introduces a periodic phase jump to the IF signal. The system incorporates only a single optical channel, largely reducing the system complexity. Experimental results show that an AOA measurement with a range of -70.8° to 70.8° is realized, with errors confined to within ±2°.

Photonics-Based Radar Jamming Signal Generation and Self-Interference Cancellation

A radar jamming signal generation scheme based on microwave photonics is proposed. This model includes frequency shifting jamming signal generation and self-interference cancellation (SIC). In the scheme, the upper dual-drive Mach–Zehnder modulator (DDMZM) of a dual-parallel dual-drive Mach–Zehnder modulator (DP-DDMZM) is used to recover the signals-of-interest (SOI) by subtracting the self-interference signal from the received radar signal. The lower DDMZM of the DP-DDMZM is utilized to shift the frequency of the optical carrier by Serrodyne modulation. The output of the DP-DDMZM is sent to a photodetector to obtain the frequency shifting jamming signal. In the experiment, the generation of velocity deception jamming and range deception jamming signals is demonstrated. The spurious suppression ratio of the generated velocity deception jamming signals is investigated. The SIC performance of the scheme for signals with different frequencies and bandwidths is also analyzed. Both velocity deception jamming and range deception jamming can be flexibly implemented with variable parameters. Both radar jamming signal generation and self-interference cancellation can be implemented with only one DP-DDMZM, which has the advantages of a simple structure and easy integration.

Precise Multiple Frequency Identification Based on Frequency-to-Time Mapping and Cross-Correlation

We propose and demonstrate a microwave frequency identification system based on frequency-to-time mapping (FTTM) and cross-correlation. The unknown microwave signals and the bidirectional chirped microwave probe signal are mixed by using a dual-drive Mach-Zehnder modulator. The mixing products are equivalently selected by a dispersion induced photonic filter and converted into electrical pulses in time domain. The unknown frequency is measured by calculating the time interval of the pulses. Moreover, a scheme based on cross-correlation is proposed to eliminate the noise interference for the pulse position acquisition. Experimentally, single and multiple frequency identification from 2-14 GHz is successfully demonstrated, and the measured frequency errors are less than ±3 MHz.

Single-channel system for joint unambiguous measurement of DFS and AOA based on serrodyne modulation.

In this paper, a photonic-assisted system for simultaneous and unambiguous measurement of the Doppler frequency shift (DFS) and angle-of-arrival (AOA) using a dual-parallel dual-drive Mach-Zehnder modulator (DP-DDMZM) is proposed and investigated. The echo signals received by two receiving antennas are applied to the radio frequency ports of one sub-DDMZM of the DP-DDMZM. The bias port of the sub-DDMZM is fed by a binary electrical signal that is used to construct two different mapping curves on the relationship between the phase difference and the power of the output intermediate frequency (IF) signal. Therefore, unambiguous AOA measurement with extended range can be realized. The transmitted signal is input into the other sub-DDMZM to implement single-sideband modulation, which is then frequency shifted based on serrodyne modulation. Both the value and direction of DFS can be derived intuitively from the frequency of the output IF signal. Simulation results show that the measurement error of unambiguous DFS measurement is no more than ±0.008H z in the range of -100k H z to 100kHz, and the measurement error of unambiguous AOA is less than ±0.2∘ in the range of -70.8∘ to 70.8°. Moreover, since the scheme does not involve the construction of multi-channels or use of any filter or polarization dependent device, the system has concise structure, high accuracy, large operating bandwidth, and strong robustness, and can be considered as a very promising solution for actual applications.

Multiband LFM waveform generation and band-selection using stimulated Brillouinscattering.

Modern radar systems are designed to simultaneously serve multiple applications such as ranging, surveillance, imaging, or warfare, which necessitates operation at multiple carrier frequencies. Linear frequency modulated (LFM) signals are inherently capable of pulse compression leading to enhanced range resolution and good signal-to-noise ratios; therefore, they are widely employed in various radar applications. In this paper, a photonic-based generation scheme for carrier frequency multiplication of LFM waveforms up to a factor of four through a single dual-drive Mach-Zehnder modulator is proposed and experimentally demonstrated. The technique is employed to produce multiband LFM having wide-bandwidth chirps (500MHz, 1GHz) as well as narrow bandwidth chirps (10, 20MHz) that are compatible with the intrinsic linewidth of stimulated Brillouin scattering (SBS). The frequency bands of the narrow bandwidth chirps are further selected through a frequency-agile Brillouin RF filter. The generated tupled chirped waveforms are at continuous multiples of the RF carrier frequency at 2, 4, 6, and 8GHz, respectively, with the first three multiples having 10MHz and the fourth multiple having 20MHz chirp bandwidth. This scheme is also experimentally verified for generating different tupled products and respective filtering through SBS at multiples of 4GHz up to 16GHz, thereby verifying the system's agility and flexibility.

Wideband‐Tunable on‐Chip Microwave Photonic Filter with Ultrahigh‐Q U‐Bend‐Mach–Zehnder‐Interferometer‐Coupled Microring Resonators

AbstractMicrowave photonic filters are a key fundamental subsystem in microwave photonics. A wideband‐tunable on‐chip microwave photonic filter (MPF), which monolithically integrates a dual‐drive Mach‐Zehnder modulator (DDMZM), is proposed with ultrahigh‐Q Mach–Zehnder‐interferometer (MZI)‐coupled microring resonators (MRRs) in cascade and a high‐speed photodetector (PD). It is the first time an MPF has been developed by introducing U‐bend‐MZI‐coupled MRRs whose resonance wavelength and 3 dB bandwidth are tunable. In particular, the ultrahigh‐Q U‐bend‐MZI‐coupled MRRs are realized with ultralow loss broadened silicon waveguides based on a modified Euler curve. For the fabricated U‐bend‐MZI‐coupled MRRs, which have an effective radius of 29 µm, the Q‐factor is as high as 1.3 × 106, while the free spectral range (FSR) is as large as 113 GHz. Furthermore, the introduction of two cascaded U‐bend‐MZI‐coupled MRRs enables the MPF to have flat‐top bandstop (or bandpass) responses with a high extinction ratio (ER) of 20–35 dB as well as a tunable 3 dB bandwidth of 0.15–3 GHz. Meanwhile, the central frequency can be tuned thermally from 2 to 40 GHz. The work provides a feasible route to realize a compact, high spectral resolution, and wideband‐tunable MPF on silicon, enabling a range of RF applications from wireless communication to flexible high‐frequency microwave photonic signal processing.

Neuromorphic regenerative memory optoelectronic oscillator.

Neuromorphic spiking information processing based on neuron-like excitable effect has achieved rapid development in recent years due to its advantages such as ultra-high operation speed, programming-free implementation and low power consumption. However, the current physical platforms lack building blocks like compilers, logic gates, and more importantly, data memory. These factors become the shackles to construct a full-physical layer neural network. In this paper, a neuromorphic regenerative memory scheme is proposed based on a time-delayed broadband nonlinear optoelectronic oscillator (OEO), which enables reshaping and regenerating on-off keying encoding sequences. Through biasing the dual-drive Mach-Zehnder electro-optic modulator in the OEO cavity near its minimum transmission point, the OEO can work in excitable regime, where localized states are maintained for robust nonlinear spiking response. Both simulation and experiment are carried out to demonstrate the proposed scheme, where the simulation results and the experimental results fit in with each other. The proposed OEO-based neuromorphic regenerative memory scheme exhibits long-term response ability for short-term excitation, which shows an enormous application potential for high-speed neuromorphic information buffering, optoelectronic interconnection and computing.

Photon statistics and quantum phase distribution for coherent optical links in the presence of phase noise from both the laser source and the RF oscillator, and dispersion

A model of photon statistics and quantum phase distribution is analyzed for coherent optical communication links in the presence of quantum phase noise, dispersion and phase noise of the radio-frequency (RF) oscillator using an in-line optical amplifier. The quantum analysis of a dual drive Mach–Zehnder modulator and the quantum transfer function for an optical field mode across an in-line amplifier is performed by taking into account both the quantum and the classical phase noises. The resulting photon statistics are compared with the semiclassical model. We analyze the quantum phase distribution by considering the Wigner quasiprobability distribution for a coherent optical link. Here, we investigate the broadening of the quantum phase distribution due to quantum phase noise of the laser, the dispersive optical fiber, the phase noise of the RF oscillator and the inevitable noise coefficient of the optical amplifier for arbitrary amplified spontaneous emission (ASE) field modes. We analytically investigate the quantum analog to the bit error rate (BER) as a function of the laser’s linewidth, the linewidth of the RF oscillator and chromatic dispersion. The results of quantum models are compared with the semiclassical model. Quantum treatment of both the BER and variance is found to agree with prior results for a single-mode ASE field in the absence of phase noise but deviate when the effect of phase noise is considered. Including phase noise effects in the amplitude in the semiclassical treatment of the BER yields a new semiclassical expression that agrees with quantum expressions of machine precision for single-mode ASE fields.

A broadband integrated microwave photonic mixer based on balanced photodetection

An integrated microwave photonic mixer based on silicon photonic platforms is proposed, which consist of a dual-drive Mach–Zehnder modulator and a balanced photodetector. The modulated optical signals from microwave photonic links can be directly demodulated and down-converted to intermediate frequency (IF) signals by the photonic mixer. The converted signal is obtained by conducting off-chip subtraction of the outputs from the balanced photodetector, and subsequent filtering of the high frequency items by an electrical low-pass filter. Benefiting from balanced detection, the conversion gain of the IF signal is improved by 6 dB, and radio frequency leakage and common-mode noise are suppressed significantly. System-level simulations show that the frequency mixing system has a spurious-free dynamic range of 89 dB·Hz2/3, even with deteriorated linearity caused by the two cascaded modulators. The spur suppression ratio of the photonic mixer remains higher than 40 dB when the IF varies from 0.5 to 4 GHz. The electrical-electrical 3 dB bandwidth of frequency conversion is 11 GHz. The integrated frequency mixing approach is quite simple, requiring no extra optical filters or electrical 90° hybrid coupler, which makes the system more stable and with broader bandwidth so that it can meet the potential demand in practical applications.Graphical

Ultrahigh-linearity dual-drive scheme using a single silicon modulator.

Here, a high-linearity dual-drive scheme using a single silicon dual-drive Mach-Zehnder modulator is presented. The bias voltages and RF amplitudes of the two driving arms are adjusted such that the nonlinearity of the transfer function of the Mach-Zehnder interferometer cancels out the nonlinear response of the arms. Using the proposed scheme, the spurious-free dynamic range of the third-order intermodulation distortion is 123.4 dB Hz6/7, which is believed to be a record-breaking value for silicon modulators. In comparison, the result obtained using a conventional single-drive scheme is 102.6 dB·Hz2/3. The proposed scheme could simplify the design of modulators and promote high-performance microwave photonic links.

Photonic-assisted generation of joint radar and communication signals with immunity to power fading

In this paper, a photonic-assisted generation of joint radar and communication signals with immunity to power fading is proposed based on a dual-polarization binary phase-shift keying (DP-BPSK) modulator. Two dual-drive Mach–Zehnder modulators (DD-MZMs) named DD-MZM1 and DD-MZM2 are respectively located on the upper and lower arms of the DP-BPSK modulator. In DD-MZM1, an intermediate frequency communication signal is single sideband (SSB) modulated on the optical carrier. At one radio frequency (RF) port of DD-MZM2, a split parabolic waveform signal is phase-modulated on the optical carrier to generate SSB radar signal, and the other RF port is used to phase modulate local oscillator signal. By simply adjusting a polarization controller, radar or communication signal can be respectively generated at different frequency band after balanced photoelectric conversion. Experiments are carried out to verify the feasibility of the scheme. Radar signals with bandwidths of 500 MHz and 1 GHz are generated. The error vector magnitude of the generated 16-QAM signal with a baud rate of 100 Msym/s is 5.42%. The frequency tunability and the immunity to power fading are also verified. The proposed method has a simple and compact structure and meets the requirement of long-distance transmission, which has potential applications in emerging intelligence scenarios.

Photonics-Assisted Analog Wideband Self-Interference Cancellation for In-Band Full-Duplex MIMO Systems With Adaptive Digital Amplitude and Delay Pre-Matching

A photonics-assisted analog wideband RF self-interference (SI) cancellation and frequency downconversion approach for in-band full-duplex (IBFD) multiple-input multiple-output (MIMO) systems with adaptive digital amplitude and delay pre-matching is proposed based on a dual-parallel Mach–Zehnder modulator (DP-MZM). In each MIMO receiving antenna, the received signal, including different SI signals from different transmitting antennas and the signal of interest, is applied to one arm of the upper dual-drive Mach–Zehnder modulator (DD-MZM) of the DP-MZM, the reference signal is applied to the other arm of the upper DD-MZM, and the local oscillator signal is applied to one arm of the lower DD-MZM. The SI signals are canceled in the optical domain in the upper DD-MZM and the frequency downconversion is achieved after photodetection. To cancel the SI signals, the analog reference signal is constructed in the digital domain, while the amplitude and delay of the constructed reference are adjusted digitally by upsampling with high accuracy. Experiments are performed when two different SI signals are employed. The genetic algorithm or least squares algorithm is combined with segmented search respectively for the SI signal reconstruction and amplitude and delay pre-matching. A cancellation depth of around 20 dB is achieved for the 1-Gbaud 16 quadrature-amplitude modulation orthogonal frequency-division multiplexing signal.

Fiber-terahertz-fiber bridge system in the 355-GHz band using a simple optical frequency comb and a photonics-enabled receiver.

This Letter demonstrates a high-speed fiber-terahertz-fiber system in the 355-GHz band using stable optical frequency comb generation and a photonics-enabled receiver. At the transmitter, a single dual-drive Mach-Zehnder modulator is employed to generate a frequency comb by driving the modulator under an optimal condition. At the antenna site, a photonics-enabled receiver consisting of an optical local oscillator signal generator, a frequency doubler, and an electronic mixer is used to downconvert the terahertz-wave signal to the microwave band. Simple intensity modulation and a direct detection method are used for transmitting the downconverted signal to the receiver over the second fiber link. To demonstrate the proof of concept, we transmitted a 16-quadrature amplitude modulation (QAM) orthogonal frequency-division multiplexing signal over a system consisting of two radio-over-fiber links and a 4 m wireless link in the 355-GHz band and achieved a line rate of 60 Gb/s. We also successfully transmitted a 16-QAM subcarrier multiplexing single-carrier signal over the system and achieved a capacity of 50 Gb/s. The proposed system can facilitate the deployment of ultra-dense small cells in high-frequency bands in beyond-5G networks.

Switchable Dual-Band Binary and Single-Band Quaternary Phase-Coded Microwave Signal Generation Using a Dual-Polarization Dual-Drive Mach–Zehnder Modulator

A switchable dual-band binary and single-band quaternary phase-coded microwave signal generator based on a single dual-polarization dual-drive Mach–Zehnder modulator (DP-DDMZM) is proposed. Two radio frequency (RF) signals are first coupled with two bipolar coded signals and then used to drive the DP-DDMZM. When the frequencies of the two RF signals are different, the generator will be in dual-band binary phase-coded mode and a dual-band binary phase-coded signal can be generated. When the frequencies of the two RF signals are the same but their phase difference is adjusted to be 90°, the generator will be in single-band quaternary phase-coded mode and a single-band quaternary phase-coded signal can be obtained. Detailed analysis is carried out to illustrate the mechanism and a proof-of-concept experiment is also performed to demonstrate the feasibility. The dual-band binary and single-band quaternary phase-coded microwave signal are both experimentally generated and their performance is evaluated. The proposed generator features the advantages of simple structure, high flexibility and stable performance, which is promising in the future multifunctional radar systems.