Photonic Ultra-wideband Research Articles

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.

A Novel Approach to Photonic Generation and Modulation of Ultra-Wideband Pulses

AbstractA novel approach to photonic generation of ultra-wideband (UWB) signals is proposed in this paper. The proposed signal generator is capable of generating UWB doublet pulses with flexible reconfigurability, and many different pulse modulation formats, including the commonly used pulse-position modulation (PPM) and bi-phase modulation (BPM) can be realized. Moreover, the photonic UWB pulse generator is capable of generating UWB signals with a tunable spectral notch-band, which is desirable to realize the interference avoidance between UWB and other narrow band systems, such as Wi-Fi. A mathematical model describing the proposed system is developed and the generation of UWB signals with different modulation formats is demonstrated via computer simulations.

Remote Radar Based on Chaos Generation and Radio Over Fiber

Abstract: An ultrawideband (UWB) radar system for remote ranging based onmicrowave-photonic chaotic signal generation and fiber-optic distribution is proposedand demonstrated experimentally. In this system, an optical-feedback semiconductorlaser with optical injection in the central office generates photonic UWB chaos as probingsignal, and two single-mode fibers transport the optical signal to the remote antennamonitoring terminal and return the corresponding echoed signal back to the centraloffice. In the remote antenna terminal, the photonic signal is transformed into microwavechaos by a fast photodetector and then launched to target by a transmitting antenna,and the echoed signal received by another antenna is converted into optical domain bymodulating a laser diode. The target ranging is achieved at the central office by correlat-ing the echoed signal with the reference signal. We experimentally realize a detectionrange of 8 m, for a free-space target, after 24-km remote distance, and achieve a rang-ing resolution of 3 cm for single target and 8 cm for double targets. In another fiber linkbranch with 15-km fiber transmission, we obtained the 2-cm ranging resolution for asingle target.Index Terms: Chaos, remote radar, semiconductor lasers.

Reconfigurable photonic ultrawideband pulse generation from an optically injected semiconductor laser

We demonstrate reconfigurable photonic ultrawideband (UWB) pulse generation by injecting a phase-modulated optical wave into a semiconductor laser. By adjusting the injection power level and phase modulation depth, the photonic UWB generator is capable of generating either a single-optical-carrier monocycle or power-efficient UWB pulses. A UWB pulse with spectral power efficiency (SPE) of 36.10% has been achieved by optimizing the injection parameters. Transmission in an 8.4 km single mode fiber results in a degradation of SPE to 27.55% without significant pulse distortion.

Photonic multi-shape UWB pulse generation using a semiconductor optical amplifier-based nonlinear optical loop mirror

We propose and demonstrate a scheme to implement photonic multi-shape ultra-wideband (UWB) signal generation using a semiconductor optical amplifier (SOA) based nonlinear optical loop mirror (NOLM). By employing the cross phase modulation (XPM) effect, cross gain modulation (XGM), or both, multi-shape UWB waveforms are generated including monocycle, doublet, triplet, and quadruplet pulses. Both the shapes and polarities of the generated pulses are flexible to adjust, which may be very useful in UWB pulse shape modulation and pulse polarity modulation.

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.

Photonic generation of ultra-wide-band doublet pulse through monolithic integration of tapered directional coupler and quantum well waveguide

We proposed and demonstrated a novel scheme of photonic ultra-wide-band (UWB) doublet pulse based on monolithic integration of tapered optical-direction coupler (TODC) and multiple-quantum-well (MQW) waveguide. TODC is formed by a top tapered MQW waveguide vertically integrating with an underneath passive waveguide. Through simultaneous field-driven optical index- and absorption- change in MQW, the partial optical coupling in TODC can be used to get a valley-shaped of optical transmission against voltage. Therefore, doublet-enveloped optical pulse can be realized by high-speed and high-efficient conversion of input electrical pulse. By just adjusting bias through MQW, 1530 nm photonic UWB doublet optical pulse with 75-ps pulse width, below -41.3 dBm power, 125% fractional bandwidth, and 7.5 GHz of -10 dB bandwidth has been demonstrated, fitted into FCC requirement (3.1 GHz~10.6 GHz). Doublet-pulse data transmission generated in optical fiber is also performed for further characterization, exhibiting a successful 1.25 Gb/s error-free transmission. It suggests such optoelectronic integration template can be applied for photonic UWB generation in fiber-based communications.

Performance evaluation of photonic UWB generation based on silicon MZM

Silicon photonics has emerged as the premier candidate for the photonic systems-on-chip (SoC). The scheme based on the silicon Mach-Zehnder modulator (MZM) to generate photonic ultra-wideband (UWB) signals is helpful to the integration of the UWB system with other optical networks on a single silicon-based chip. In this paper, according to the influence of the nonlinear free carrier dispersion (FCD) effect and the free carrier absorption (FCA) effect, the performance of two typical UWB generation schemes is numerically analyzed. The double side-band UWB (DSB-UWB) generation scheme needs the DC reverse bias which increases the complexity of the modulator and there is a residual chirp resulting from the FCD effect even the push-pull operation is adopted. The quasi single-sideband UWB (QSSB-UWB) generation scheme doesn't have these problems. However there is the asymmetric amplitude peak in the generated UWB signal. The property of the large singal modulation is also investigated to improve the signal-to-noise ratio (SNR).

Simulation analysis of a photonic ultrawideband pulse generator by using a dual-parallel Mach–Zehnder modulator

This study analyzes a photonic ultrawideband pulse generator by using a dual-parallel Mach-Zehnder modulator. A simple configuration capable of generating two popular types of ultrawideband pulse shape, Gaussian monocycle and doublet, is proposed. The generated ultrawideband pulses have very high quality, and the exact waveform is tunable with respect to parameter settings. By changing the time delay between two-path driving pulses applied to the upper and lower sub-Mach-Zehnder modulator of the dual-parallel Mach-Zehnder modulator, the generated ultrawideband pulses can be switched from Gaussian monocycle to doublet. The proposal is first analyzed and then validated by simulations. Results of the study demonstrate that it can offer a realistic solution to photonic ultrawideband pulse generation.

Influence of large signal modulation on photonic UWB generation based on electro-optic modulator

Various schemes based on electro-optic modulators have been reported to generate ultra-wideband (UWB) signals in the optical domain, but the availability of these methods always relies on small signal modulation. In this paper, the influence of large signal modulation on two typical schemes, representing two major categories of external-modulator-based photonic UWB generation schemes, is analytically and numerically studied. While the quasi single-sideband UWB (QSSB-UWB) pulse can maintain its shape, the Gaussian UWB (GUWB) generation scheme suffers serious modulation distortion when the phase modulation index is greater than π/6. The modulation distortion would have negative impact on the receiver sensitivity when the signal is sent to a correlation receiver.

Photonic Ultrawideband Pulse Generation With HNL-DSF-Based Phase and Intensity Modulator

We propose and experimentally demonstrate a photonic ultrawideband (UWB) pulse (monocycle and doublet) generator based on a highly nonlinear dispersion-shifted fiber (HNL-DSF). The pulsed pump, located in the anomalous group-velocity dispersion regime of the HNL-DSF, performs as both an intensity and a phase modulator in our scheme. We experimentally prove, for the first time to the best of our knowledge, that the UWB doublet pulse can be generated when the optical carrier is located at the center of a narrow tunable filter's passband. Furthermore, the encoded doublet signal, fully compliant with the Federal Communications Commission (FCC) regulations, is transmitted at 950 Mb/s through a 25-km single-mode fiber without introducing any obvious pulse distortion.

Range Extension and Channel Capacity Increase in Impulse-Radio Ultra-Wideband Communications

We theoretically analyze the channel capacity of a 5th-order Gaussian pulse-based ultra-wideband (UWB) system and experimentally demonstrate 2 Gbit/s UWB-over-fiber transmission systems incorporating wireless transmission. Both electrical and photonic UWB pulse generation methods are employed and its performance is compared. By utilizing optimum UWB pulse design and employing a digital signal processing (DSP) receiver, a bit-error-rate above the forward error correction (FEC) limit for 8 meters of wireless emission is obtained in our photonic generation UWB system. A noticeable increase in the channel capacity is achieved compared to previously reported results.

Photonic Ultra-Wideband 781.25-Mb/s Signal Generation and Transmission Incorporating Digital Signal Processing Detection

The generation of photonic ultra-wideband (UWB) impulse signals using an uncooled distributed-feedback laser is proposed. For the first time, we experimentally demonstrate bit-for-bit digital signal processing (DSP) bit-error-rate measurements for transmission of a 781.25-Mb/s photonic UWB signal over fiber links. The DSP algorithm is described, the generated UWB signal is shown to comply with the U.S. Federal Communications Commission requirements, and transmission of 1.71times10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> UWB bits over fiber is demonstrated without error.