Photonic Arbitrary Waveform Generation Research Articles

High-stable and reconfigurable photonic generation of radio-frequency arbitrary waveforms with multi-tone inputs

Conventional temporal pulse shaping (TPS) for radio frequency (RF) arbitrary waveform generation (RF AWG) based on the Fourier transform relation between the input–output waveform pair requires the electronic AWG to generate RF input signal, which greatly limits the output waveform diversity due to the relative low sampling rate and bit resolution of electronic AWG, i.e., high-fidelity square waveforms are hard to be achieved since high-resolution broadband Sinc input signals are difficult to be generated by current commercial electronic AWGs. The approaches based on TPS with phase modulation incorporating with iterative algorithms can relatively improve the waveform diversity by applying the optimal phase information. However, time-consuming iterative algorithms significantly restrict the waveform reconfigurability, i.e., desired RF waveforms cannot be generated in real-time. We propose a novel high-stable and reconfigurable RF AWG scheme with multi-tone inputs, which aims to improve the output waveform diversity with simple manipulation and high stability. In our design, any desired RF waveform can be achieved in real-time by simply adjusting the power values of multi-tone inputs. A proof-of-concept experiment was implemented, which fully verified the feasibility of the approach. The system performance in terms of output waveform stability was investigated in detail. As no electronic AWG is employed and no iterative algorithms are required, the proposed design provides a promising solution for high-performance reconfigurable photonic-based RF arbitrary waveforms generation.

Photonic generation of microwave arbitrary waveforms using stimulated Brillouin scattering and Sagnac loop

Photonic generation of microwave arbitrary waveforms using stimulated Brillouin scattering and Sagnac loop

Photonic arbitrary waveform generation based on the temporal Talbot effect.

In this paper, we propose a novel photonic approach for generating arbitrary waveform. The approach is based on the property of real-time Fourier transform in the temporal Talbot effect, where the spectrum of the modulating analog signal is converted into the output time-domain waveform in each period. We present a concise and strict theoretical framework to reveal the relationship of real-time Fourier transform between the optical signals before and after the dispersion. A proof-of-concept experiment is implemented to validate the presented theoretical model. We propose to generate symmetrical or asymmetrical arbitrary waveforms by using double-sideband or single-sideband modulation, respectively, which is verified by simulation results. It is shown that the given approach can be used to generate a repetition-rate multiplied optical pulse train with arbitrary waveform by simply using a multi-tone RF signal with appropriate frequencies and powers.

Photonic Arbitrary Waveform Generation With Three Times the Sampling Rate of the Modulator Bandwidth

A new method for high-speed photonic arbitrary waveform generation using optical sinc-pulse sequences and Mach-Zehnder modulators is presented, enabling a three- to four-fold increase in sampling rate compared to the bandwidth of the used modulator for generating the pulses and an N -fold increase compared to the bandwidth of the incorporated electronics, with N as the number of parallel branches. Proof of concept experimental results, using conventional off-the-shelf fiber components have been presented in this study. Due to its simplicity and the possibility to achieve high sampling rates with low bandwidth photonic and electronic equipment, this method is beneficial for integration on a silicon photonics platform.

Broadband Cognitive Radio Enabled by Photonics

Cognitive radio is considered as a possible disruptive force to improve the spectral resource efficiency through sensing and interacting with the environment. Traditional electrical technologies to implement the cognitive radio face challenges in terms of bandwidth, resolution, and speed. In this paper, the concept and architecture of broadband cognitive radio systems enabled by photonics are proposed. Key microwave photonic techniques for the architecture are reviewed, including the photonics-based spectrum sensing, the photonic arbitrary waveform generation, the photonics-based self-interference cancellation processing, and the microwave photonic dechirp processing and radar imaging. A preliminary demonstration of a cognitive radar system enabled by photonics is performed. The future possible research directions on this topic are discussed.

A photonic scheme for the generation of dual linear chirp microwave waveform based on the external modulation technique and its airborne application

Due to high frequency and large time bandwidth product; photonic generation and processing of arbitrary microwave waveforms has been an interesting topic in recent time. Here, a relatively new photonic technique has been proposed for the generation of a dual linear chirp microwave waveform in Ku-band. In this method two single drive Mach–Zehnder Modulators are cascaded at minimum transmission point and in push–pull mode. Theoretical analysis and simulation are developed by giving a complete mathematical model. As the result of this methodology, a dual linear chirp microwave waveform in Ku-band with relatively large bandwidth is generated. Comparative analysis is done in the present cascading technique with dual parallel Mach–Zehnder Modulator (DPMZM) technique. Range-Doppler coupling of the radar system has been investigated with the help of an ambiguity function diagram of the generated waveform. Results have analyzed through MATLAB simulation and verified by experimental results.

Photonic arbitrary waveform generator based on Taylor synthesis method.

Arbitrary waveform generation has been widely used in optical communication, radar system and many other applications. We propose and experimentally demonstrate a silicon-on-insulator (SOI) on chip optical arbitrary waveform generator, which is based on Taylor synthesis method. In our scheme, a Gaussian pulse is launched to some cascaded microrings to obtain first-, second- and third-order differentiations. By controlling amplitude and phase of the initial pulse and successive differentiations, we can realize an arbitrary waveform generator according to Taylor expansion. We obtain several typical waveforms such as square waveform, triangular waveform, flat-top waveform, sawtooth waveform, Gaussian waveform and so on. Unlike other schemes based on Fourier synthesis or frequency-to-time mapping, our scheme is based on Taylor synthesis method. Our scheme does not require any spectral disperser or large dispersion, which are difficult to fabricate on chip. Our scheme is compact and capable for integration with electronics.

Silicon-Based Integrated Microwave Photonics

Integrated microwave photonics is an emerging field in which photonic integrated technologies are employed to realize on-chip integration of microwave photonic systems with the aim to enrich the functionalities and enhance the system performance. Silicon photonics, as one of the various photonic integrated technology platforms, has attracted worldwide attention to achieve microwave photonic system integration for its compatibility with the current CMOS technology and its potential of seamless integration with electronics. In this paper, an overview about our recent work on silicon-based integrated microwave photonics is presented with an emphasis on silicon-based on-chip photonic arbitrary microwave waveform generation and microwave signals processing.

Photonic generation of low phase noise arbitrary chirped microwave waveforms with large time-bandwidth product.

We present a photonic approach for generating low phase noise, arbitrary chirped microwave waveforms based on heterodyne beating between high order correlated comb lines extracted from frequency-agile optical frequency comb. Using the dual heterodyne phase transfer scheme, extrinsic phase noises induced by the separate optical paths are efficiently suppressed by 42-dB at 1-Hz offset frequency. Linearly chirped microwave waveforms are achieved within 30-ms temporal duration, contributing to a large time-bandwidth product. The linearity measurement leads to less than 90 kHz RMS frequency error during the entire chirp duration, exhibiting excellent linearity for the microwave and sub-THz waveforms. The capability of generating arbitrary waveforms up to sub-THz band with flexible temporal duration, long repetition period, broad bandwidth, and large time-bandwidth product is investigated and discussed.

Characterization of the photonic generation of phase-coded RF signals based on pulse shaping and frequency-to-time mapping

Photonic generation of arbitrary waveforms based on pulse shaping and frequency-to-time mapping is of great interest since it offers an effective way to generate complex signals with large bandwidth. In this paper, we mathematically study the photonic generation of phase-coded radio frequency (RF) signals based on pulse shaping and frequency-to-time mapping in detail. By mathematically analyzing the process of signal generation and utilizing the less restrictive dispersion requirement, a design criterion for the generation of well-shaped phase-coded RF waveforms is presented, by which we can properly set the spatial light modulator in the pulse shaper and dispersion in the system according to the carrier frequency and modulating frequency of the desired waveform. In addition, the maximum achievable time-bandwidth product of phase-coded RF signals that can be generated is estimated. The theory is verified by numerical and experimental results. The presented results can be used to guide the design of a photonic system for the generation of high-quality phase-coded RF signals.

Photonic generation of W-band arbitrary waveforms with high time-bandwidth products enabling 39 mm range resolution

Ultrabroadband millimeter-wave and subterahertz waveforms offer significant potential, from ultrahigh-speed communications to high-resolution radar. Electronic generation of broadband arbitrary waveforms at these frequencies suffers from limited digital-to-analog converter speed and high timing jitter. Photonic-assisted techniques, such as those based on optical shaping and frequency-to-time mapping, can overcome these difficulties. Nevertheless, previous photonic arbitrary waveform generation demonstrations are confined to microwave and low millimeter-wave frequencies due to limited optical-to-electrical conversion bandwidth. Here, by utilizing cutting-edge photodetector technology, we report the first generation, wireless transmission, and measurement of substantially complex and highly stable arbitrary waveforms in the W-band (75–110 GHz). These waveforms exhibit high time-bandwidth products up to 600, arbitrarily extendable repetition periods, and phase-noise performance substantially better than state-of-the-art electronic arbitrary waveform generators. The utility of the generated waveforms is demonstrated in multi-target ranging, where a depth resolution of 3.9 mm, unprecedented in the W-band, is achieved over more than 5 m.

Photonic Radio-Frequency Arbitrary Waveform Generation With Maximal Time-Bandwidth Product Capability

We present an innovative photonic strategy to generate arbitrary microwave and millimeter-wave signals with maximal time-bandwidth product capability and broadly tunable center frequency. The proposed approach incorporates high-resolution pulse shaping, optical interferometry, and the concept of frequency-to-time mapping in order to enable independent control over the temporal amplitude, temporal phase, and center frequency of the generated waveforms. Numerical simulation and experimental results validate that the time-bandwidth product of these pulses is equal to the upper bound set by the number of independent pulse shaper control elements, extending to more than twice that of conventional frequency-to-time mapping techniques. We thus demonstrate a record photonic arbitrary waveform generation time-bandwidth product of ~589. Also, a length 15 Costas sequence realization is implemented to further portray the potentials of this technique. Detailed analysis of the repeatability and stability of these waveforms as well as higher order dispersion compensation is provided.

Photonic arbitrary waveform generation based on crossed frequency to time mapping

Microwave photonic arbitrary waveform generation based on incoherent frequency-to-time-mapping (FTTM) accompanied by intersymbol interference, so called crossed FTTM (CFTTM). The pulse shape can be defined and tuned by properly adjusting the spectrum shaper (symbol shape) and the degree of intersymbol interference. UWB-, triangular-, rectangle-, comb- and user-defined pulse shapes are experimentally obtained.

Photonic generation of arbitrary waveforms based on incoherent wavelength-to-time mapping

We demonstrate experimentally a radio frequency arbitrary waveform generator using the incoherent wavelength-to-time mapping technique. The system is implemented by amplitude modulation of a broadband optical resource whose spectrum is reshaped by a programmable optical pulse shaper and transmitted over a single mode fiber link. The shape of the generated waveform is controlled by the optical pulse shaper, and the fiber link introduces a certain group velocity delay to implement wavelength-to-time mapping. Assisted by the flexible optical pulse shaper, we obtain different shapes of optical waveforms, such as rectangle, triangle, and sawtooth waveforms. Furthermore, we also demonstrate ultra-wideband generation, such as Gaussian monocycle, doublet, and triplet waveforms, using the incoherent technique.

A time-domain photonic arbitrary waveform generator

A time domain photonic arbitrary waveform generator (PAWG) scheme based on multi-wavelength optical differential quadrature phase shift keying modulation in combination with differential detection is proposed and experimentally demonstrated. The time domain method shows advantages of large time-bandwidth product, good flexibility, fast waveform refreshing rate, and high waveform quality over the frequency domain method. In contrast with other proposed time domain PAWGs or photonic digital-to-analog converters, our PAWG proposal shows a greater dynamic range and a larger noise margin due to its bipolar output, and possesses good scalabilities both in resolution and sampling rate. Assisted with the integration technology, this PAWG presents a good prospect for broad range practical applications in future.

Photonic generation of microwave arbitrary waveforms

In this paper, techniques to generate microwave arbitrary waveforms based on all-fiber solutions are reviewed, with an emphasis on the system architectures based on direct space-to-time pulse shaping, spectral-shaping and wavelength-to-time mapping, temporal pulse shaping, and photonic microwave delay-line filtering. The generation of phase-coded and frequency-chirped microwave waveforms is discussed. The challenges in the implementation of the systems for practical applications are also discussed.

Photonic arbitrary waveform generation applicable to multiband UWB communications

A novel photonic structure for arbitrary waveform generation (AWG) is proposed based on the electrooptical intensity modulation of a broadband optical signal which is transmitted by a dispersive element and the optoelectrical processing is realized by combining an interferometric structure with balanced photodetection. The generated waveform can be fully reconfigured through the control of the optical source power spectrum and the interferometric structure. The use of balanced photodetection permits to remove the baseband component of the generated signal which is relevant in certain applications. We have theoretically described and experimentally demonstrated the feasibility of the system by means of the generation of different pulse shapes. Specifically, the proposed structure has been applicable to generate Multiband UWB signaling formats regarding to the FCC requirements in order to show the flexibility of the system.

Broadband photonic arbitrary waveform generation using a frequency agile laser at 15 μm

We use a pulse-compression chirp-transform algorithm to generate broadband photonic arbitrary waveforms. A phase-locked frequency agile laser provides the needed broadband frequency scans. We theoretically show and experimentally demonstrate that the residual laser frequency errors do not significantly alter the waveform generation. The experiment exhibits features such as the operation at the telecom wavelength of 1.5 μm, the counterpropagating, crossed-polarized beam configuration, and the storage of the initial waveform in the active medium. The last specificity gives access to large time-bandwidth product values.

Ultrabroad-bandwidth arbitrary radiofrequency waveform generation with a silicon photonic chip-based spectral shaper

Ultrabroad-bandwidth radiofrequency pulses offer significant applications potential, such as increased data transmission rate and multipath tolerance in wireless communications. Such ultrabroad-bandwidth pulses are inherently difficult to generate with chip-based electronics due to limits in digital-to-analog converter technology and high timing jitter. Photonic means of radiofrequency waveform generation, for example, by spectral shaping and frequency–time mapping, can overcome the bandwidth limit in electronic generation. However, previous bulk optic systems for radiofrequency arbitrary waveform generation do not offer the integration advantage of electronics. Here, we report a chip-scale, fully programmable spectral shaper consisting of cascaded multiple-channel microring resonators, on a silicon photonics platform that is compatible with electronic integrated circuit technology. Using such a spectral shaper, we demonstrate the generation of burst radiofrequency waveforms with programmable time-dependent amplitude, frequency and phase profiles, for frequencies up to 60 GHz. Our demonstration suggests potential for chip-scale photonic generation of ultrabroad-bandwidth arbitrary radiofrequency waveforms.

Photonic arbitrary waveform generator based on dispersion of multiwavelength pulse sequence

We propose and demonstrate a novel method for a radio-frequency photonic arbitrary waveform generator based on a tunable, multiwavelength pulse sequence and wavelength-to-time mapping induced by fiber chromatic dispersion. We simulate and experimentally demonstrate the generation of an arbitrary waveform and obtain burst single-tone, frequency modulation, and phase modulation signals. We also analyze the potential and primary limitations in the proposed architecture.