Dual-parallel Mach-Zehnder Modulator Research Articles

Simple DFS and AOA simultaneous measurement scheme without directional ambiguity with co-frequency self-interference signal cancellation

A photonic method based on a dual-polarization dual-parallel Mach–Zehnder modulator (DPol-DPMZM) for the simultaneous measurement of the Doppler frequency shift (DFS) and angle of arrival (AOA) of microwave signals is proposed and demonstrated by simulation. The upper arm of each sub-DPMZM is driven by the echo and self-interference signals from the antenna, while the lower arm is driven by the reference signal 1 and reference signal 2. The phase and amplitude of the reference signal 1 are adjusted to match the interference signals for achieving the self-interference cancellation (SIC). At the central office (CO), the DFS and AOA can be acquired in real time without directional ambiguity by processing the two downconverted low-frequency tones in the photocurrent. The simulation results show that the presence of the SI signal will seriously interfere with the observation of the SOI frequency and waveform, and the self-interference cancellation depth of about 42 dB can be obtained after the SIC. The measurement errors of the DFS without direction ambiguity are within 0.2 Hz. After the Hilbert transformation of the intermediate frequency (IF) signal, the AOA can be measured from −87.31∘ to +87.31∘ with errors less than 3.9°. The system has a large bandwidth, excellent real-time performance, and better invisibility, and is expected to be used in modern electronic warfare systems.

A channelized broadband and high-resolution microwave instantaneous multi-frequency measurement system based on Fabry-Perot Filter and Stimulated Brillouin Scattering

A broadband high-resolution microwave instantaneous multi-frequency measurement (IMFM) system based on a Fabry-Perot filter (FPF) and Stimulated Brillouin Scattering (SBS) is proposed. In the system, the 14-line flat optical frequency comb (OFC) in the first branch is input to dual-parallel Mach-Zehnder modulator (DPMZM) for carrier suppressed single sideband modulation (CS-SSB), so that the microwave signal to be measured is loaded onto the sideband of the 14-line OFC. The FPF is employed for periodic filtering to roughly determine the frequency band of the captured microwave signal. Subsequently, the demultiplexer (De-mux) is utilized to channelize the captured frequency band, which serves as a pump light input to the high nonlinear fiber (HNLF). By setting the center frequency spacing between the OFCs in the second and third branches with the channelized pump light in the first branch is equal to the Brillouin frequency shift, the frequencies of the microwave signal under measurement are determined based on the fine frequency selection characteristic of the SBS effect. This achieves an enhancement in measurement resolution while ensuring measurement bandwidth. Simulation experiments indicate that by adjusting the frequency shifter and center frequency of the FPF, the proposed IFM system can realize measurement ranges of 0.6–13.5 GHz, 13.6–26.5 GHz, and 26.6–39.5 GHz, the measurement resolution is 0.1 GHz, and the measurement error is ±0.05 GHz.

A Reconfigurable Local Oscillator Harmonic Mixer with Simultaneous Phase Shifting and Image Rejection

A Reconfigurable Local Oscillator Harmonic Mixer with Simultaneous Phase Shifting and Image Rejection

Design and investigation of filterless sixtuple RoF upconversion system with improved sideband to carrier suppression ratio using MZM extinction ratio variance

Abstract In this work, millimeter wave generation of sixtuple frequency scheme using dual parallel Mach–Zehnder modulator configuration has been investigated. The proposed scheme is mathematically analyzed and its performance is evaluated using software optisystem v.18. The vital parameters of both Mach–Zehnder modulator and phase of radio frequency local oscillator are properly adjusted for upconversion of 10 GHz radio frequency drive signal into 60 GHz mm wave. The impact of Mach–Zehnder modulator extinction ratio on radio frequency sideband suppression ratio, optical sideband suppression ratio and third sideband to carrier suppression ratio, is evaluated. An improved 63 dB third sideband to carrier suppression ratio is achieved at increased extinction ratio of Mach–Zehnder modulator. Impact of bias point drift and electrical phase shift on sideband suppression ratios are evaluated. Further, millimeter wave signal of 6–60 GHz tunability is realized by applying radio frequency local oscillator signal from 1 to 10 GHz.

A Microwave Photonic Frequency-Doubling Phase Shifter Based on Dual-Parallel Mach–Zehnder Modulators

A microwave photonic frequency-doubling phase shifter with a broad bandwidth and large tuning range is proposed in this paper. Frequency doubling and phase shifting are realized by processing the input microwave signal in the optical domain at a dual-drive dual-parallel Mach–Zehnder modulator (DD-DPMZM) and a dual-parallel Mach–Zehnder modulator (DPMZM). The input signal is split into two branches through a 90-degree hybrid splitter. One signal is sent to the DD-DPMZM to achieve a phase-shifted carrier-suppressed up-sideband by tuning the bias voltage, and the other is sent to the DPMZM to realize a carrier-suppressed down-sideband. By beating the phase-shifted up-sideband and the down-sideband at a photodetector (PD), the input signal is frequency doubled and phase shifted. The proposed frequency-doubling phase shifter is simulated. The results show that the frequency-doubled signal has a phase-tuning range from 0 to 360 degrees. In addition, the influence of the amplitude and phase unbalance of the 90-degree hybrid splitter on the magnitude variation and phase deviation of the frequency-doubling phase shifter is studied.

Generation of arbitrary microwave waveforms based on a dual-parallel Mach–Zehnder modulator driven by a single sinusoidal RF signal

Generation of arbitrary microwave waveforms based on a dual-parallel Mach–Zehnder modulator driven by a single sinusoidal RF signal

Photonic generation and transmission for an X-band dual-chirp waveform with frequency multiplication and power-fading compensation.

The generation of an X-band dual-chirp waveform, which is capable of pulse compression, plays an important role in radar, electric warfare, and satellite communication systems. With the development of applications such as multi-static radar, transmission over long distances has attracted considerable attention. In this paper, a photonic system for X-band dual-chirp waveform generation and transmission based on frequency multiplication and power-fading compensation is put forward and experimentally carried out. Based on a compact dual-parallel Mach-Zehnder modulator (DPMZM), the dual-chirp waveforms of 8.6-9.6GHz and 9.6-10.6GHz are generated by an RF carrier of 4.8GHz and transmitted through a 40km single-mode fiber (SMF) spool. The dispersion-induced power fading of the chirp waveform is compensated for by about 13dB. The full width at half maximum (FWHM) and the peak-to-sidelobe ratio (PSR) of the compressed pulses are 1ns and 11.5dB, respectively. Moreover, the compensation of power fading in the entire X-band is verified to demonstrate the applicability of our system. By flexibly adjusting the bias voltage of the built-in phase shifter, the system can be applied in more scenarios.

Generation of a Flat Optical Frequency Comb via a Cascaded Dual-Parallel Mach–Zehnder Modulator and Phase Modulator without Using the Fundamental Tone

Under the conventional scheme to generate an optical frequency comb (OFC) using an electro-optic modulator (EOM), the frequency interval of the OFC is determined via the frequency of the fundamental tone of the radio frequency (RF) driving signals. In this work, we use two harmonics without the fundamental tone to drive two EOMs, where the frequency interval of the generated flat OFC is the frequency of the fundamental tone. The orders of the two harmonics are coprime. Specifically, one harmonic drives the first branch of the dual-parallel Mach–Zehnder modulator (DPMZM) only, and the other harmonic drives the phase modulator (PM). The flatness of the OFC is achieved by adjusting the amplitude and phase of the RF driving harmonics as well as the bias of the EOM. Both a simulation and an experiment were carried out to verify the effectiveness of the proposed scheme. When the second harmonic drives the DPMZM and the third harmonic drives the PM, an 11-comb line OFC is generated, where the flatness of the OFC was 0.63 dB and 0.65 dB under the simulation and experiment, respectively. When the third harmonic drives the DPMZM and the second harmonic drives the PM, a 13-comb line OFC is generated, where the flatness of the OFC was 0.62 dB and 0.95 dB under the simulation and experiment, respectively. We also investigate the performance of the generated OFC when one harmonic drives two branches of the DPMZM and the other harmonic drives the PM. The comparison of the OFCs’ performance demonstrates the effectiveness of the proposed scheme.

Tunable radar compound coherent jamming signal generation based on microwave photonics.

A photonic-assisted scheme to generate radar compound coherent jamming signals based on a dual-parallel Mach-Zehnder modulator (DP-MZM) is proposed and experimentally demonstrated. The received linear frequency-modulated (LFM) signal is interrupted sampled and comb spectrum modulated by a DP-MZM. After photoelectric conversion, the compound coherent jamming signal, which combines the comb spectrum modulation jamming (CSMJ) and interrupted sampling repeater jamming (ISRJ), is generated. In the experiment, the generated coherent jamming signals have a 1-GHz bandwidth centered at 8 GHz and 18 GHz, respectively. The tunability of the frequency interval for CSMJ, the duty cycle, and the sampling frequency for ISRJ are verified. After pulse compression (PC), 10 false target groups are evenly distributed over a radial distance of 120 m, and the total number of false targets reaches to 50. The jamming effectiveness in radar imaging is also demonstrated. To the best of our knowledge, photonic-assisted CSMJ and ISRJ compound jamming generation is proposed for the first time. The proposed scheme is compact, wideband, and tunable, which shows a good potential application in the future electronic warfare system.

Photonic instantaneous microwave frequency measurement based on frequency-phase mapping with high precision

This paper presents an instantaneous microwave frequency measurement scheme based on a frequency-phase mapping technique. In our scheme, a low-frequency (LF) reference signal and two microwave signals with a relative time delay are modulated on the optical carriers via two dual-parallel Mach–Zehnder modulators. The generated electrical signal has the same frequency as that of the LF reference signal, but with a phase shift, which depends on the microwave signal frequency and the time delay. Therefore, a linear frequency-phase mapping function with a high slope is constructed, which improves the accuracy of the whole frequency measurement range. The scheme has a compact structure without an optical filter and polarization devices, which enhances the long-term stability of the system. The simulation shows that our scheme has a 4.1–40 GHz frequency measurement range with errors less than ±0.04 GHz.

High‐accuracy optical delay measurement based on linear frequency sweeping technology

AbstractA high‐accuracy and wide‐range optical delay measurement method based on linear frequency modulation (LFM) of a microwave source is proposed, which can measure the delay of each channel in a parallel multichannel interference structure. The light wave emitted by the light source is injected into the dual‐parallel Mach‒Zehnder modulator (DPMZM) as a carrier wave. The LFM microwave signal is loaded into the radio frequency ports of the DPMZM through a 90° hybrid couple, and the bias voltages of the DPMZM are adjusted to make it work in carrier suppression single sideband (CS‐SSB) modulation mode. The CS‐SSB optical signal output by the modulator enters the test links, including a Mach‒Zehnder interference loop composed of the reference arm and the device under test arm. Then, the output optical signal of the interference loop is input into a photodetector, and the intermediate frequency (IF) signals are obtained by the beat frequency. The frequency of the IF signal is obtained through data acquisition and fast Fourier transform calculation. Thus, the delay time is calculated. By increasing or decreasing the LFM signal scanning time, the delay measurement range can be extended, or the measurement accuracy over a short distance can be improved. The feasibility of this method is verified by experiments, and the delay of parallel multichannel measurement is carried out.

Silicon-Organic Hybrid Electro-Optic Modulator and Microwave Photonics Signal Processing Applications.

Electro-optic modulator (EOM) is one of the key devices of high-speed optical fiber communication systems and ultra-wideband microwave photonic systems. Silicon-organic hybrid (SOH) integration platform combines the advantages of silicon photonics and organic materials, providing a high electro-optic effect and compact structure for photonic integrated devices. In this paper, we present an SOH-integrated EOM with comprehensive investigation of EOM structure design, silicon waveguide fabrication with Slot structure, on-chip poling of organic electro-optic material, and characterization of EO modulation response. The SOH-integrated EOM is measured with 3 dB bandwidth of over 50 GHz and half-wave voltage length product of 0.26 V·cm. Furthermore, we demonstrate a microwave photonics phase shifter by using the fabricated SOH-integrated dual parallel Mach-Zehnder modulator. The phase shift range of 410° is completed from 8 GHz to 26 GHz with a power consumption of less than 38 mW.

Photonic generation of dual-mode multi-format chirp microwave signals.

In this paper, we present a novel, to the best of our knowledge, photonic scheme for the generation of dual-mode multi-format chirp microwave signals, utilizing a dual-drive dual-parallel Mach-Zehnder modulator (DD-DPMZM). By inputting a single-chirp signal and controlling the input binary sequences, the proposed method can generate up-, down-, dual-, or triangular-chirp signals in both pulse and continuous-wave modes. Moreover, the duty cycle of the generated chirp signals in the pulse mode can be easily adjusted by manipulating the injected binary sequences. The compact structure of the proposed scheme eliminates the need for polarization control in signal switching and avoids the use of any optical filter. Experimental verification confirms the feasibility of our approach, while also pointing towards its promising applications in multi-functional radar systems.

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.

Coherent stepped-frequency waveform generation based on recirculating microwave photonic frequency conversion.

We propose a novel method for generating coherent and wideband stepped-frequency waveforms using recirculating microwave photonic frequency conversion (MWP-FC). By injecting a narrowband signal into an MWP-FC loop utilizing a dual-parallel Mach-Zehnder modulator (DPMZM), the signal frequency is continuously converted to produce a stepped-frequency waveform with a wide bandwidth. Within the MWP-FC loop, photo-electric conversion is achieved based on self-mixing detection, where the optical phase noise can be suppressed, guaranteeing stability and coherence of the generated signal. In a proof-of-concept experiment, a stepped-frequency signal with a frequency interval of 2 GHz and a bandwidth of about 16 GHz and a stepped-frequency chirp signal with a frequency interval of 3 GHz and a bandwidth of about 15 GHz are generated. In addition, coherence of the generated signals is verified by coherent integration and de-chirping.

Photonic generation of frequency-doubling Nyquist pulses using external modulation.

In this paper, an approach to generate frequency-doubling sinc-shaped optical Nyquist pulses based on external modulation is proposed and demonstrated. First, four flat optical frequency comb (OFC) lines are obtained after optical carrier suppression modulation in a dual-electrode Mach-Zehnder modulator. Then an optical interleaver is introduced to split the phase-locked OFC into two paths, of which one is transmitted to a dual-parallel Mach-Zehnder modulator for quadrupling RF modulation and another is applied to the remodulated signal to acquire comb lines with equal intervals. Thus, a phase-locked 12-line flat OFC with equal frequency intervals and corresponding Nyquist pulses is finally obtained, and Nyquist pulses at 2.5GHz, 5GHz, 10GHz, and 15GHz are achieved.

Generation of GHz line-spacing tunable optical frequency combs using Talbot effects.

In this paper, the generation of GHz line-spacing tunable optical frequency combs (OFCs) was demonstrated using an electro-optical (EO) Talbot laser and a phase modulator. In the EO Talbot laser, the frequency shifting was realized with a dual-parallel Mach-Zehnder modulator (DPMZM) working for carrier-suppressed single-sideband modulation. The PM was employed to achieve the spectral Talbot effect and compensate the phase introduced by the temporal Talbot effect in the laser loop. Arbitrary control of OFC line-spacing was realized using temporal and spectral Talbot effects. The principle of this OFC generator was theoretically modeled. In the experiments, the 2GHz line spacing of an OFC was multiplied to be 4GHz, 6GHz, 8GHz, and 10GHz. The frequency spacing of the OFC can also be multiplied with a fractional factor of 3/4, 7/2, 8/5, and 10/7, which was confirmed by simulations.

Comparison of performance for third order immune photonic transmission link incorporating phase shifters and biased optimized dual parallel Mach–Zehnder modulator

Abstract This paper presents a comprehension on the linearization arrangements achieved through dual drive dual parallel Mach–Zehnder (DD-DPMZM) by changing bias voltages of sub-modulators and adjusting phases of RF signals. These arrangements comprise of a DD-DPMZM and electric phase shifters. For single sideband (SSB) modulation in sub-modulators of DD-DPMZM, power at intermodulation is found to be 43 dB and 61 dB for the linearized and convention single modulator link respectively. Thus, 28 dB of improvement in suppression of third order intermodulation distortion is reported for the first arrangement of linearization. For quadrature modulation in upper MZM and optical carrier suppression (OCS) modulation in lower modulator, almost complete suppression of IMD3 terms are demonstrated and found to be better performance arrangement for bias optimized dual parallel Mach–Zehnder modulator based linearization link.

Photonics-Based Broadband Radar With Coherent Receiving for High-Resolution Detection

A microwave photonics radar with interference-suppressed high-resolution detection ability is proposed and experimentally demonstrated based on optical frequency quadrupling and coherent receiving de-chirping. Which is achieved by using a dual-parallel Mach-Zehnder modulator to perform base-band signal frequency quadrupling in transmitter, and an optical coherent receiver to realize balanced photonic in-phase/ quadrature (I/Q) de-chirping of the broadband radar echoes in receiver. Thanks to the frequency multiplication, a wideband radar transmitting signal can be generated with low speed electron devices. Meanwhile, interference-free detection by suppressing undesired common-mode interferences and image frequency could be achieved with balanced photonic I/Q de-chirping broadband radar echoes. In the experiment, a photonics-based K-band radar with a bandwidth of 8 GHz is demonstrated, corresponding to a resolution better than 2.0 cm. In addition, the balanced photonic I/Q de-chirping receiver achieves an image-rejection ratio of 40.4 dB. The proposed radar detection system is a promising candidate in interference-suppressed high-resolution radar application.

Filterless frequency 32-tupling millimeter-wave generation based on two cascaded dual-parallel Mach–Zehnder modulators

This study proposed a novel scheme for filterless frequency 32-tupling millimeter wave (MMW) generation based on two cascaded dual-parallel Mach–Zehnder modulators (DPMZMs). When the MZMs are biased on a maximum transmission point and the phase difference of the radio frequency (RF) driving voltage between the two MZMs in DPMZM is π/2, the DPMZM can be used as a quadrupler, which can generate ±4n-order optical sidebands. When the phase difference of the RF driving voltage between the two DPMZMs is π/4, the two cascaded DPMZMs can be used as an octupler, which can generate ±8n-order optical sidebands. After the ±8th-order optical sidebands are suppressed by adjusting the modulation index of MZMs, the center carrier is suppressed by a polarization multiplexing structure, and the ±8n (n > 2) sidebands are ignored because their amplitudes are very small. The main optical components remaining in the output of the two cascaded DPMZMs are ±16th-order optical sidebands, which are beaten in the photodetector to obtain frequency 32-tupling MMW. The theoretical and experimental optical sideband suppression ratios (OSSRs) and radio frequency spurious suppression ratios (RFSSRs) are 53.7 dB and 53.53 dB and 47.7 dB and 47.33 dB, respectively. The experimental and theoretical analysis is consistent, which verifies the feasibility of the scheme. The influence on the OSSR and RFSSR of the generated signals by the extinction ratio and DC bias drift of the MZMs, the initial phases and the amplitudes of the RF drive signal, and the azimuth of the polarization controller (PC) are investigated.