Single Dual-drive Mach-Zehnder Modulator Research Articles

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.

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.

Single-modulator, direct frequency comb spectroscopy via serrodyne modulation.

Traditional electro-optic frequency comb spectrometers rely upon the use of an acousto-optic modulator (AOM) to provide a differential frequency shift between probe and local oscillator (LO) legs of the interferometer. Here we show that these modulators can be replaced by an electro-optic phase modulator (EOM) which is driven by a sawtooth waveform to induce serrodyne modulation. This approach enables direct frequency comb spectroscopy to be performed with a single dual-drive Mach-Zehnder modulator (DD-MZM), allowing for lower differential phase noise. Further, this method allows for simpler production of integrated photonic comb spectrometers on the chip scale.

Multiband dual- and cross-LFM waveform generation using a dual-drive Mach–Zehnder​ modulator

Linear frequency modulation (LFM) signals are widely used in modern radar systems owing to their intrinsic pulse compression capability but are restricted due to a limited range-Doppler resolution. On the other hand, dual- or cross-LFM signals have complementary LFM waveforms at the same time instant that reduces the range-Doppler coupling and thus improving range-Doppler resolution. We propose a simple microwave-photonic-based approach to generate multiband dual- and cross-LFM waveforms using only a single dual-drive Mach–Zehnder modulator (DDMZM). A theoretical analysis is carried out, which is modeled and verified through experiments. Dual- and cross-LFM waveforms at a carrier frequency of 6 GHz and 18 GHz with a bandwidth of 2 GHz is generated by controlling the DC and RF bias of the DDMZM. The tunability of the carrier frequency from 3 GHz to 9 GHz is also verified. A range resolution of 6.3 cm for dual- and cross-LFM waveforms, is obtained with a time-bandwidth-product (TBWP) of 20,000. The proposed technique is a promising solution for dual- and cross-LFM waveform generation in two-band multipurpose radar systems.

Inverse design of programmable optical frequency comb using deep learning

Optical frequency comb (OFC) has important applications in measurement, communication, military and other fields. Usually, OFC needs to be designed according to different applications. However, the existing methods to design the operating parameters of the OFC generators are time-consuming, inefficient, and difficult to achieve optimal results. In this paper, a novel method of inversely designing OFC using deep learning, which is real-time and can improve the performance of the generated OFC, is proposed and applied to an OFC generator based on a single dual-drive Mach–Zehnder modulator. In this method, according to the required target OFC, the trained neural network can be used to inversely design the corresponding parameters. Using this inverse design method, the generated OFC not only is highly consistent with the target OFC, but also has the programmability of comb-line number, comb-line power, side mode suppression ratio, and comb spacing. Moreover, the proposed method can be utilized for more complicated OFC generator, and is an inspiration for efficient design of OFC.

Optical Analog Noise Encryption With Adaptive Recovery of Two-Dimensional Keys

An optical analog noise encryption system with adaptive recovery of two-dimensional keys is proposed and demonstrated using regular triangle (RT)adaptive algorithm in an optical self-interference cancellation system at the designated receiver. Analog noise encryption and data modulation are performed in a single dual-drive Mach-Zehnder modulator at the transmitter, while decryption is performed in an electro-absorption modulated laser based adaptive cancellation system at the receiver. The weight and delay of the analog noise form the two-dimensional orthogonal encryption keys. Two sets of fingerprints are securely pre-shared for only once between the transmitter and designated receiver and stored before real transmission to ensure that both sides are legitimate users and facilitate adaptive key recovery when using RT adaptive algorithm at the legitimate receiver for retrieving the orthogonal keys. Without receiving the keys from the transmitter, the legitimate receiver is able to adaptively find the two orthogonal keys even under dynamic key changing scenario. In the experiment, a 3.5 GHz wideband analog noise is used to encrypt a 10 Gbps 16 quadrature amplitude modulation (QAM) orthogonal frequency division multiplexing (OFDM) signal at 1.75 GHz. By recovering the orthogonal keys using RT algorithm and the unique pre-shared fingerprints, the designated receiver has successfully decrypted the encrypted signal by removing the analog noise as wide as 3.5 GHz, 28 dB stronger than the sensitive signal, which is by far the best performance in an optical analog noise encryption system.

Subcarrier multiplexed radio over fiber system with optical single sideband modulation

Abstract A subcarrier multiplexed radio over fiber (RoF) system using optical single sideband (OSSB) modulation is proposed. OSSB modulation reduces the bandwidth requirements and also combats the radio frequency (RF) power fading issue due to the dispersive effects in optical fiber. Subcarrier multiplexing (SCM) is a technique used to transmit multiple RF signals through the same optical fiber to utilize its large bandwidth. A theoretical analysis showed that OSSB generation with a number of subcarriers can be done by Hilbert transform method employing a single dual drive Mach–Zehnder Modulator (MZM). This technique is very relevant in the emerging 5G standards which require accesses of multiple standards simultaneously (5G, LTE, and Wi-Fi). This paper demonstrates a low cost solution of OSSB-RoF system and more effective utilization of the spectrum. Simulations results showing satisfactory reception of signals up to 50 km.

High-Performance Fully Integrated Silicon Photonic Microwave Mixer Subsystems

We experimentally demonstrate two silicon photonic based mixer subsystems for applications in next gen fronthaul networks, defense, and communications for space, avionics, and vehicles. The mixer subsystems leverage emerging integrated microwave photonics technology through the AIM Photonics foundry. Our work demonstrates the potential for full integration of spectrally agile functions to enable seamless upconversion and downconversion over wide instantaneous bandwidths. Characterization of the frequency converting architectures focuses on analog metrics including gain, linearity, and noise figure. The first architecture represents the simplest architecture for practical frequency conversion on-chip using a single dual-drive Mach–Zehnder modulator and single photodetector. The second architecture, using dual parallel single-drive Mach–Zehnder modulators and balanced detection, represents the first silicon photonic downconverter with electrical-in, electrical-out frequency conversion fully on-chip; additionally, this architecture demonstrates the widest bandwidth reported among mixers of similar integration level on any material platform. Simulations using characterized parameters of components are performed and demonstrate accurate prediction of analog metrics for both mixer architectures. Using these simulations, we predict the performance of improved, fully integrated implementations of the characterized architectures using state-of-the-art platforms, demonstrating that high performance integrated microwave photonic frequency conversion is achievable.

Photonic generation of programmable coherent linear frequency modulated signal and its application in X-band radar system.

A photonic generation scheme of a programmable coherent linear frequency modulated (LFM) signal is proposed and experimentally demonstrated. By heterodyne beating an agile optical frequency comb (OFC) with a fixed OFC, LFM signals in different bands can be obtained. The two OFCs are generated independently from two arms of a single dual-drive Mach-Zehnder modulator (DDMZM) and are then propagated through the same optical path, thus naturally ensuring the coherence of the LFM pulses at the minimum cost. The generation of the agile OFC only requires a sweeping intermediate frequency (IF) signal with the far lower center frequency and smaller bandwidth than the generated LFM signal. And by precisely controlling this IF signal, parameters of the LFM signal can be flexibly adjusted such as the center frequency, bandwidth, time duty, and sweeping pattern. In addition, envelope-tailorable LFM pulsed signals are further realized by pre-distorting the IF signal, supporting future multifunctional radar applications. We then establish a complete X-band radar system. The pulse-to-pulse phase coherent integration of the generated LFM signal enhances the signal-to-noise ratio of echo signals by ∼24 dB. A 5.8 cm range resolution is finally achieved, which is comparable to more complex photonic radar systems. This compact DDMZM based scheme not only improves the radar performance by realizing coherence pulses but also provides full control of these pulses, evidently benefiting the system integration and multifunctionality in future advanced radar applications.

Performance analysis of CSRZ-DQPSK transmitter configurations for SBS tolerance in single mode fiber link

This paper investigates the SBS tolerance of two reduced complexity Carrier Suppressed Return to Zero- Differential Quadrature Phase Shift Keying (CSRZ-DQPSK) transmitter configurations and comparison with conventional 3 MZM scheme is reported. One scheme utilizes a single DD-MZM (Dual Drive Mach Zehnder Modulator) and a MZM (Mach Zehnder Modulator). Another configuration uses a single DD-MZM (Dual Drive Mach Zehnder Modulator). The link performance is evaluated for 10 Gbps data rate in a 50 Km single mode fiber link. From the simulation results, it is observed that two and one MZM based configurations provide 3 dB improvement in SBS threshold compared to the standard three MZM based implementation. Also, the performance of 2 MZM is slightly better than the single MZM configuration. As the input power is increased beyond SBS threshold, the roll off of Q- Factor is found to be 0.3/dBm for 3 MZM scheme where it is 0.05/dBm and 0.1/dBm for the 2 MZM and 1 MZM schemes. The BER performance is better at higher power levels, for the one and two MZM cases.

基于单个双驱动马赫-曾德尔调制器的宽且平坦的可调谐光学频率

基于单个双驱动马赫-曾德尔调制器的宽且平坦的可调谐光学频率

Self-interference cancellation using dual-drive Mach-Zehnder modulator for in-band full-duplex radio-over-fiber system.

In this paper, we design a self-interference cancellation (SIC) scheme for in-band full-duplex (IBFD) radio-over-fiber (RoF) systems based on wavelength division multiplexing passive optical network (WDM-PON) architectures. By using a single dual-drive Mach-Zehnder modulator (DDMZM), over various bands up to 25 GHz, this proposed SIC system can simultaneously cancel the in-band downlink (DL) self-interference and modulate the recovered uplink (UL) radio frequency (RF) signal. OFDM-RF signals are used to study the cancellation performances of optical SIC system for the first time. Experimental results show more than 32-dB cancellation depth over 250-MHz bandwidth within 1-GHz RF band, as well as 300-MHz within 2.4-GHz and 400-MHz within 5-GHz band. As for 2.4-GHz RF band, 390.63-Mbps 16-QAM OFDM UL signal buried by strong in-band DL OFDM signal is well recovered. For broadband applications, more than 27-dB cancellation depth is achieved over 10 MHz~25 GHz wideband, so that up to 25 GHz RF band can be expanded for this IBFD WDM-RoF system.

Photonic Generation of 3-D UWB Signal Using a Dual-Drive Mach-Zehnder Modulator

We propose and experimentally demonstrate a new method to generate a 3-D ultrawideband (UWB) signal by utilizing a dual-drive Mach-Zehnder modulator (DDMZM). Three degrees of freedom of the generated 3-D UWB signal are pulse position, pulse phase, and pulse amplitude. In this scheme, each radio frequency (RF) port of the DDMZM is modulated by a combination of two encoded signals with different amplitudes. By properly adjusting the amplitudes of the encoded signals and the bias voltages of the two RF ports, a 5-Gb/s 3-D UWB signal with a central frequency of 3.5 GHz and a 10-dB fractional bandwidth of 163% is successfully generated by using only a single DDMZM.

Photonic generation of arbitrarily phase-modulated microwave signals based on a single DDMZM

We propose and demonstrate a compact and cost-effective photonic approach to generate arbitrarily phase-modulated microwave signals using a conventional dual-drive Mach-Zehnder modulator (DDMZM). One arm (arm1) of the DDMZM is driven by a sinusoidal microwave signal whose power is optimized to suppress the optical carrier, while the other arm (arm2) of the DDMZM is driven by a coding signal. In this way, the phase-modulated optical carrier from the arm2 and the sidebands from the arm1 are combined together at the output of the DDMZM. Binary phase-coded microwave pulses which are free from the baseband frequency components can be generated when the coding signal is a three-level signal. In this case, the precise π phase shift of the microwave signal is independent of the amplitude of the coding signal. Moreover, arbitrarily phase-modulated microwave signals can be generated when an optical bandpass filter is attached after the DDMZM to achieve optical single-sideband modulation. The proposed approach is theoretically analyzed and experimentally verified. The binary phase-coded microwave pulses, quaternary phase-coded microwave signal, and linearly frequency-chirped microwave signal are experimentally generated. The simulated and the experimental results agree very well with each other.

Photonic generation of background-free millimeter-wave ultra-wideband pulses based on a single dual-drive Mach–Zehnder modulator

We propose a novel photonic approach for generating a background-free millimeter-wave (MMW) ultra-wideband (UWB) signal based on a conventional dual-drive Mach-Zehnder modulator (DMZM). One arm of the DMZM is driven by a local oscillator (LO) signal. The LO power is optimized to realize optical carrier suppressed modulation. The other arm is fed by a rectangular signal. The MMW UWB pulses are generated by truncating the continuous wave LO signal into a pulsed one in a photodetector (PD). The generated MMW UWB signal is background-free by eliminating the baseband frequency components because the optical power launched to the PD keeps constant all the time. The proposed method is theoretically analyzed and experimentally verified. The generated MMW UWB signal centered at a frequency of 26 GHz meets the Federal Communications Commission spectral mask very well.

Photonic microwave downconverter based on an optoelectronic oscillator using a single dual-drive Mach-Zehnder modulator

A novel and compact photonic microwave downconverter is proposed and experimentally demonstrated based on an optoelectronic oscillator (OEO) using a single dual-drive Mach-Zehnder modulator (DMZM). The DMZM is used to simultaneously convert the input RF signal into an optical signal, form an OEO for RF carrier extraction, and downconvert the optical RF signal to the baseband. In the experiment, a 2-Gb/s NRZ coded 10.66-GHz RF signal is successfully downconverted to the baseband. In addition, a microwave receiver for wireless high-definition (HD) video transmission is built and verified based on the proposed downconverter. The experiment results confirm that the proposed downconverter has simple configuration, good downconversion performance and very stable operation.

Photonic generation of a phase-coded microwave signal based on a single dual-drive Mach–Zehnder modulator

A compact scheme for photonic generation of a phase-coded microwave signal using a dual-drive Mach-Zehnder modulator (DMZM) is proposed and experimentally demonstrated. In the proposed scheme, the radio frequency (RF) carrier and the coding signal are sent to the two RF ports of the DMZM, respectively. By properly setting the amplitude of the coding signal and the bias voltage of the DMZM, an exact π-phase-shift phase-coded microwave signal is generated. The proposed scheme has a simple structure since only a single DMZM is required. In addition, good frequency tunability is achieved because no frequency-dependent electrical devices or wavelength-dependent optical devices are applied. The feasibility of the proposed scheme is verified by experiment. 2 or 2.5 Gb/s phase-coded 10 and 20 GHz microwave signals are successfully generated.

Flexible RF-Based Comb Generator

A comb generator based on feeding a single dual drive Mach-Zehnder modulator with a sinusoidal radio frequency (RF) at one arm and its double frequency at the other arm is demonstrated. Our comb generator benefits from the superposition of optical subcarriers generated by the fundamental and its second harmonic. We demonstrate flexibility in center wavelength tunability, subcarrier spacing, and subcarrier count. For a fundamental frequency at, e.g., 6.25 GHz, our comb generator can produce 9, 5, 4, or 3 optical subcarriers with a spectral flatness of <; 1.2 dB. We successfully demonstrate to the best of our knowledge, the generation of the largest number of comblines requiring the lowest drive signal with the least components within the field of RF-generated combs.

基于单个双驱动马赫-曾德调制器的40Gb/s星型16-QAM光发射机

We propose a 40-Gb/s star 16-ary quadrature amplitude modulation (16-QAM) transmitter using a single dual-drive Mach-Zehnder modulator (DDMZM). This transmitter is demonstrated through experiment and simulation and shows the advantage of simplicity for implementation. Simulation results indicate that error free performance could be achieved for the generated signal after 80-km standard single-mode fiber (SSMF) transmission with coherent detection scheme.

Advanced data modulation techniques for WDM transmission

This article discusses the various schemes for generating typical advanced modulation formats in terms of configuration and cost, and particularly presents some recently proposed configurations for optical data generation with better performance or reduced components, including pulsed multichannel source generation for return-to-zero (RZ)-based WDM application, multichannel dual-mode pulse source for carrier-suppressed RZ (CSRZ)-based WDM application, CSRZ and CSRZ differential phase shift keyed (DPSK) signal generation using a single Mach-Zehnder modulator (MZM) together with an electrical mixer, chirped RZ generation with reduced modulator number, and RZ/CSRZ-DPSK generation using a single dual-drive MZM and optical minimum shift keying (MSK).