Ultrawideband Monocycle Pulses Research Articles

Ultra-wideband doublet signal generation with tunable notch band based on delay-line filter

ABSTRACT A novel and simple scheme to generate Ultra-wideband (UWB) doublet signal with tunable notch band based on a tunable delay-line filter is presented. The first-order differentiation is realized by a dual-drive Mach–Zehnder modulator (DD-MZM), which differentiates the Gaussian pulses to the monocycle pulses. Subsequently, the UWB monocycle pulses are transmitted to an optical delay-line filter implemented by a balanced photo-detector and a tunable delay line for both differentiation and photodetection. Consequently, the desired UWB doublet signal can be obtained with a 10-dB bandwidth of 8.75 GHz. Besides, the polarity reversibility of the generated doublet signal is demonstrated by changing the bias voltage of the DD-MZM. Moreover, the desired notch can be introduced in the generated frequency spectrum to eliminate the interference between the existing narrowband systems and the UWB systems. And the tunability of the band-notched position is implemented by simply adjusting the delay time of the delay-line filter. The feasibility of the presented scheme is investigated by mathematical models and simulations.

All-optical regenerative technique for width-tunable ultra-wideband signal generation

We demonstrate all-optical generation of width-tunable mono-cycle pulses for ultra-wideband communication. It has been shown that the width of the mono-cycle pulses can be tuned dynamically by simply varying the power of the optical signal. We also investigate the regenerative property of the nonlinear medium-based technique for the generation of mono-cycle pulses. For the purpose of comparison, ultra-wideband mono-cycle pulses are also generated through the optical delay line-based technique. It has been demonstrated through numerical simulations that the nonlinear medium-based technique is highly resilient to amplified spontaneous emission noise that is induced over the optical signal. Furthermore, we have shown that the highly nonlinear fiber-based nonlinear medium performs better than the semiconductor optical amplifier-based medium. Bit error rate measurements are taken for different values of optical signal-to-noise ratios in order to elaborate our work.

Photonic UWB pulse generation and OOK, PPM, BPSK modulation for WDM systems based on twin-core fiber

We propose and demonstrate an approach for optical ultra-wideband (UWB) monocycle pulses generation by employing a phase modulator (PM) and twin-core fiber (TCF). Based on phase modulation to intensity modulation (PM-IM) conversion principle, multi-wavelength and polarity-reversed ultra-wideband (UWB) monocycle pulses are generated simply by making the optical carrier wavelength located at the positive or negative sloop of the periodic comb-transmission spectrum of TCF. The generated UWB monocycles with different optical carrier wavelengths are studied and analyzed. In addition, multiple modulation formats such as on-off keying (OOK), pulse position modulation (PPM) and binary phase shift keying (BPSK) are implemented. Simulation results show that the proposed scheme can offer a realistic solution to photonic UWB pulse generation and modulation for WDM systems.

Photonic generation of filter-free ultrawideband monocycle and doublet signal using single semiconductor optical amplifier in counter-propagation scheme

We propose and demonstrate a flexible and filter-free method to generate ultrawideband monocycle and doublet pulses utilizing cross-gain modulation in a semiconductor optical amplifier. The counter-propagation scheme and UWB-over-fiber technology is implemented by exploiting dispersion-induced pulse broadening effect in a single-mode fiber. Owing to the counter-propagation scheme, the pump and probe light can be the same wavelength, which could provide the system better dispersion performance.

Amplitude and Phase Modulation of UWB Monocycle Pulses on a Silicon Photonic Chip

We demonstrate both the amplitude and bi-phase modulation of ultrawideband (UWB) monocycle pulses using silicon microring modulator. The integrated silicon ring modulator generates the monocycle pulse train and modulates it simultaneously. By applying different driving voltages, the amplitude and phase-modulated UWB signal with a data rate of 2.5 Gb/s are achieved. The ring modulator can be thermally tuned for a free spectral range with a $\sim 50$ -mW power consumption.

Ultrawideband monocycle pulse generation based on polarization modulator and low speed electrical NRZ signal

A novel ultrawideband (UWB) monocycle pulse generation system by modulating a polarization modulator (PolM) with a low speed electrical nonreturn-to-zero (NRZ) signal is proposed, which significantly reduce the bandwidth requirement of the driving signal. At each bit transition of the input NRZ signal, two polarity-reversed Gaussian pulses are generated. By properly setting the delay between these two Gaussian pulses, an optical UWB monocycle pulse can be generated. Biphase modulation (BPM) can be realized by electrically switching the polarization direction at the output of PolM, if an electrically tunable arbitrary wave plate (AWP) is employed.

Ultra Wideband Monocycle pulse generation using SRD and Coupled line band pass filter with reduced ringing level

Ultra Wideband Monocycle pulse generation using SRD and Coupled line band pass filter with reduced ringing level

Polarity-reversed ultra-wideband monocycle pulse generation with dual-channel multicasting in a photonic crystal fiber

This paper proposes and demonstrates a novel scheme of a two-channel-output ultra-wideband monocycle pulse generator consisting of a 100 m dispersion-flattened highly nonlinear photonic crystal fiber and two optical bandpass filters. Based on the cross-phase modulation effect in a dispersion-flattened highly nonlinear photonic crystal fiber, two polarity-reversed ultra-wideband monocycle pulses simultaneously output from two different channels are successfully achieved by appropriately locating the probe wavelength at the left linear slope and the right linear slope of the two optical bandpass filters transmission spectra, respectively. The full width at half-maximum and a fractional bandwidth of 24 ps and 260% for a positive pulse, 24 ps and 251% for a negative pulse are obtained. Moreover, the influences of input signal powers, the polarization misalignment between the data light and the continuous wave probe light, and probe wavelength variation on the double output ultra-wideband signals quality are also investigated. The results show that the system has some tolerance to both the input signal power fluctuation and the slight polarization mismatch and even can efficiently operate with a widely tunable wavelength range. This makes it very attractive for engineering applications in future multiuser ultra-wideband-over-fiber communication systems.

Reconfigurable UWB Pulse Generation Based on a Dual-Drive Mach–Zehnder Modulator

We propose and experimentally demonstrate a reconfigurable ultrawideband (UWB) pulse generation scheme by using a dual-drive Mach-Zehnder modulator (DDMZM). In the proposed method, two phase modulators of the DDMZM are respectively driven by properly designed electrical signals. By carefully setting the parameters of the two electrical signals and the bias voltage of the DDMZM, different UWB pulses can be achieved at the interference output of the DDMZM. A proof-of-concept experiment verifies the feasibility of the proposed method. Photonic generations of UWB monocycle, doublet, triplet, and quintuple pulses have been successfully demonstrated, with central frequencies of 4.69, 4.69, 5.47, and 6.25 GHz and fractional bandwidths of 150%, 133%, 186%, and 75%, respectively.

UWB Monocycle Generator Based on the Non-Linear Effects of an SOA-Integrated Structure

In this letter, we propose and experimentally demonstrate a novel and single structure to generate ultra-wideband (UWB) pulses by means of the cross-phase modulation present in a semiconductor optical amplifier unified structure. The key components of this system is an integrated Mach-Zehnder interferometer with two semiconductor optical amplifiers and an optical processing unit. The fusion of these two components permits the generation and customization of UWB monocycle pulses. The polarity of the output pulses is easily modified through the single selection of a specific input port. Moreover, the capacity of transmitting several data sequences is demonstrated and the potentiality to adapt the system to different modulation formats is analyzed.

A UWB pulse generation based on a phase modulator and programmable filter

A simple scheme for the ultra-wideband (UWB) pulse generation based on a phase modulator and programmable filter is proposed and experimentally demonstrated. By locating the center wavelength of two tunable lasers at left and right linear slope of the filter, polarity-reversed monocycle pluses are generated. A section of single mode fiber is utilized to introduce proper time delay between the pair of UWB monocycle pulses. By switching the programmable filter between bandpass filter and notch filter, positive and negative doublet pulse can be obtained additionally. The generated UWB pulses are measured in both time and frequency domain.

A Novel Subnanosecond Monocycle Pulse Generator for UWB Radar Applications

A novel ultra-wideband (UWB) monocycle pulse generator with good performance is designed and demonstrated in this paper. It contains a power supply circuit, a pulse drive circuit, a unique pulse forming circuit, and a novel monopolar-to-monocycle pulse transition circuit. The drive circuit employs wideband bipolar junction transistors (BJTs) and linear power amplifier transistor to produce a high amplitude drive pulse, and the pulse forming circuit uses the transition characteristics of step recovery diode (SRD) effectively to produce a negative narrow pulse. At last, the monocycle pulse forming circuit utilizes a novel inductanceLshort-circuited stub to generate the monocycle pulse directly. Measurement results show that the waveform of the generated monocycle pulses is over 76 V in peak-to-peak amplitude and 3.2 ns in pulse full-width. These characteristics of the monocycle pulse are advantageous for obtaining long detection range and high resolution, when it is applied to ultra-wideband radar applications.

UWB monocycle pulse generation based on colourless silicon photonic integrated circuit

Ultra-wideband monocycle pulse generation is experimentally demonstrated on a silicon photonic circuit with a monolithically integrated wavelength-tunable phase-intensity modulation converter and a waveguide germanium photodetector. A fractional bandwidth of 166% is achieved and modulation with a 2.5 Gbit/s test data pattern was demonstrated.

A Novel Approach to All-Optical Generation of Ultra-Wideband Signals

The generation of ultra-wideband signals in the optical domain is highly desirable for ultra-wideband-over-fiber systems, which has recently become a topic of interest. In this article, a novel and simple approach to achieve all-optical generation of ultra-wideband signals is proposed, which is based on delaying and superimposing optical Gaussian pulses with opposite polarities. The proposed system is capable of generating both ultra-wideband monocycle and doublet pulses, and the polarity of the generated ultra-wideband monocycle pulses can be fast-switched to implement pulse polarity modulation with the required bit pattern. A model to describe the proposed system is developed, and the generation of ultra-wideband signals is demonstrated with simulations and a proof-of-concept experiment.

Photonic ultrawideband impulse radio shape modulation based on dual-filter tuning

A simple and flexible photonic scheme for the generation of ultrawideband (UWB) pulse shape modulation based on dual-filter tuning is proposed and experimentally demonstrated. By launching a Gaussian signal into a phase modulator, the UWB polarity-switchable monocycle is generated at the output of two optical bandpass filters by adjusting the central wavelengths of the dual-filter appropriately. The doublet pulses with inverted polarities are obtained by combining the pair of UWB monocycle pulses under proper time delay. Meanwhile, with a predefined code pattern and controlling the optical path difference of the two monocycle pulses, the pulse shape modulation can be performed.

An Improved Ultra-Wideband, Ultra-Short Monocycle Pulse Generator

This paper presents an improved ultra-wideband monocycle pulse generator circuit based on step recovery diode. This pulse generator circuit uses short-circuit microstrip transmission line to generate the Gaussian pulse the monocycle pulse. The improved pulse-shaping network employs two schottky diodes and a MESFET to suppress the pulse ringing. The SRD model was built in RF simulation software ADS, and then the design and simulation of the pulse generator circuit was accomplished using this model. The experiments showed an monocycle pulse of 400ps pulse width with good symmetry. The measured results agreed with the simulation.

Edge-Triggered Ultra-Wideband Pulse Shaper Using Polarization-to-Intensity Conversion

A simple edge-triggered and chirp-free ultra-wideband (UWB) monocycle pulse shaper was proposed and demonstrated utilizing a nonlinearly operated polarization-to-intensity converter, which mainly consists of a polarization modulator (PolM), two polarization controllers (PCs), and a time-delay device. As static phase shift of the incident light φ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> =π, a 500-MHz monocycle pulse sequence with 10-dB bandwidth of 10 GHz and fractional bandwidth of 133% was obtained while a 250-MHz electrical quasi-square-wave was applied on the PolM. In addition, polarity switch of the UWB monocycle pulse can be realized by adjusting the bias voltage of the PolM or controlling the PC.

Photonic ultrawideband impulse radio generation and modulation over a fiber link using a phase modulator and a delay interferometer

We propose and experimentally demonstrate a simple and flexible photonic scheme for generation and modulation of ultrawideband (UWB) using a phase modulator and a fiber delay interferometer (DI)-based multichannel frequency discrimination. By introducing a Gaussian signal to the phase modulator, the UWB polarity-switchable doublet pulses can be achieved by combining the pair of UWB monocycle pulses with inverted polarities at the DI outputs under proper time delay. Furthermore, the pulse shape modulation, pulse position modulation, and on-off keying can be performed by coding the electrical data patterns and adjusting the time delay between the two monocycle pulses. Only a laser source introduced in the architecture guarantees the excellent dispersion tolerance over 75 km optical fiber link for UWB pulse sequence, which has potential application in future high-speed UWB impulse radio over optical fiber access networks.

UWB Monocycle Generation and Bi-Phase Modulation Based on Mach–Zehnder Modulator and Semiconductor Optical Amplifier

We propose and experimentally demonstrate an approach in generating a pair of polarity-reversed ultra-wideband (UWB) monocycle pulses by using a Mach-Zehnder modulator (MZM) and a semiconductor optical amplifier (SOA). The monocycle polarity is controlled by adjusting the bias voltage of the MZM to make the bias point located at the positive or the negative slope of the modulation curve. The generated UWB monocycles with different injection currents of SOA, different bias voltages of MZM, different optical pulse widths, and different optical carrier wavelengths are experimentally studied and analyzed. The bi-phase modulation (BPM) of monocycle pulse by applying nonreturn-to-zero (NRZ) data to the radio frequency (RF) port of MZM is also proposed and investigated.

Bismuth Nonlinear Optical Fiber for Photonic Ultrawideband Radio-Signal Processing

The feasibility of using a bismuth-oxide-based nonlinear optical fiber (Bi-NLF) for the implementation of ultrawideband (UWB) radio-signal-processing schemes is experimentally investigated. The use of two different types of nonlinear signal processors for the generation of UWB pulses is demonstrated. One processor uses cross-phase modulation for monocycle pulse generation, whereas the other uses nonlinear polarization rotation for doublet pulse generation. It is experimentally shown that UWB monocycle and doublet pulses can be successfully generated using the Bi-NLF-based nonlinear signal processors. Moreover, the system performance for the generation of UWB pulses is evaluated by performing a transmission experiment over a 20-km-long nonzero dispersion-shifted fiber (NZ-DSF) link. Error-free and penalty-free UWB doublet signal transmission is achieved.