Ultra-wideband Monocycle Research Articles

An All-Optical Transformer From Differential NRZ Data to Ultra-Wideband Pulse Stream

We propose and experimentally demonstrate a compact and cost-effective scheme based on a fiber Sagnac structure to realize real time conversion from differential nonreturn-to-zero (NRZ) data to ultra-wideband (UWB) pulse stream. The proposed conversion system for the UWB signal generation consists of a single-wavelength laser, a phase modulator, several polarization controllers, and optical couplers. Due to the optical interference between the two phase-modulated light waves with slight phase difference in the Sagnac loop, two sharp optical pulses with opposite polarities are obtained. With proper time delay, a UWB monocycle pulse stream is generated from the original differential NRZ data. Our proposed method gives a reliable, easy, and low-cost transformer from differential NRZ signal to UWB pulse stream, and no high-speed arbitrary waveform generator (AWG) is required in this all-optical transformer.

Photonic generation of ultrawideband signals by exploiting gain saturation of dark pump pulse with double undershoots in a highly nonlinear fiber

We have proposed and theoretically demonstrated an alternative photonic scheme to generate ultrawideband (UWB) doublet pulses based on gain saturation effect in one piece of highly nonlinear fiber (HNLF). A flexible format swap between UWB doublet and monocycle pulses can be successfully realized by properly tuning the optical tunable delay line (ODL). Moreover, the key parameters for UWB pulse, including the center frequency (Fc), 10 dB bandwidth (BW 10dB), and fractional bandwidth (FBW), are also investigated with Fc being Einstein shift when the doublet pulse transforms into the monocycle pulse. Finally, our proposed scheme exhibits good performance that the obtained UWB pulse can have a FBW of > 100% at the Fc of ~ 7 GHz and UWB-over-fiber technology is also implemented without dispersion management.

UWB Impulse Radio Transmitter Using an Electrooptic Phase Modulator Together With a Delay Interferometer

A simple ultra-wideband (UWB) impulse radio transmitter is experimentally demonstrated using an electrooptic phase modulator (PM) and a delay interferometer (DI). By applying an electrical nonreturn-to-zero (NRZ) baseband signal to the PM, a pair of optical Gaussian pulses with opposite polarities is generated at the two output ports of the DI. By properly setting the delay between these two polarity-reversed optical Gaussian pulses using an optical delay line (ODL) component, an optical UWB monocycle pulse is generated. Pulse amplitude modulation of the UWB monocycle pulse can also be achieved by driving the PM with an NRZ baseband signal at a flexible bit rate. Experimental results verify that the proposed scheme can be used to simultaneously generate and amplitude modulate the UWB monocycle pulse. Furthermore, both the shape and polarity of the generated UWB monocycle pulse can be easily controlled by appropriately adjusting the delay of the ODL. Pulse polarity modulation of the generated UWB monocycle can also be realized by electrically switching the bias voltage of the DI.

UWB CMOS Monocycle Pulse Generator

A low-complexity fully integrated ultrawideband (UWB) monocycle pulse generator realized in 90-nm CMOS technology by ST-Microelectronics is presented. The circuit provides a monocycle pulse when activated by a negative edge of an external trigger signal provided by a microcontroller by exploiting the operating principle of nonlinear waveform shapers. This pulse generator represents a building block of an innovative wearable system-on-chip UWB radar on silicon for cardiopulmonary monitoring. On-chip measurements show that the pulse generator provides monocycle pulses with a duration time equal to 380 ps and a peak-to-peak amplitude of 660 mV (including the losses of the microprobes, cables, and electrostatic-discharge-protected pads), which are in very good agreement with the postlayout simulations. The power consumption is 19.8 mW from a 1.2-V power supply.

Ultra-wideband monocycle generation by using electroabsorption modulator and polarization differentiation method

A novel scheme of ultra-wideband pulse generation is proposed and experimentally demonstrated. The scheme is based on polarization differentiation control in an electroabsorption modulator. The optical structure is simple. Ultra-wideband monocycle pulses with a 10-dB bandwidth of 8.0 GHz have been generated. This generation system has the potential for large bandwidth, low-voltage operation. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2817–2819, 2010; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25610

Simultaneous multi-channel CMW-band and MMW-band UWB monocycle pulse generation using FWM effect in a highly nonlinear photonic crystal fiber

We propose and experimentally demonstrate a scheme to simultaneously realize multi-channel centimeter wave (CMW) band and millimeter wave (MMW) band ultra-wideband (UWB) monocycle pulse generation using four wave mixing (FWM) effect in a highly nonlinear photonic crystal fiber (HNL-PCF). Two lightwaves carrying polarity-reversed optical Gaussian pulses with appropriate time delay and another lightwave carrying a 20 GHz clock signal are launched into the HNL-PCF together. By filtering out the FWM idlers, two CMW-band UWB monocycle signals and two MMW-band UWB monocycle signals at 20 GHz are obtained simultaneously. Experimental measurements of the generated UWB monocycle pulses at individual wavelength, which comply with the FCC regulations, verify the feasibility and flexibility of proposed scheme for use in practical UWB communication systems.

60-GHz Ultra-Wideband Radio-Over-Fiber System Using a Novel Photonic Monocycle Generation

An impulse-radio ultra-wideband (UWB) photonic generation system targeting high user density in-flight communications with simultaneous ranging capabilities in the 60-GHz radio band is proposed and demonstrated experimentally and the implementation cost is analyzed. Impulse-radio UWB monocycles are employed for signaling. The monocycles are generated employing a pulsed laser and a differential photoreceiver with phase shifting. Optical frequency up-conversion is performed employing a low-frequency RF carrier and a Mach-Zehnder electrooptical modulator operating in the nonlinear regime. In the experiment, Gaussian monocycles at a 1.244-Gbit/s data rate with 3.8-GHz bandwidth are generated and up-converted to 57 GHz. The performance of the 57-GHz UWB signal after the transmission over a standard single-mode fiber at in-cabin distances up to 100 m is studied. The experimental results show that good quality UWB pulses can be obtained with the proposed system. The impact of the system parameters on performance including wireless transmission and associated cost is analyzed, indicating that a high number of UWB access nodes can be cost-effectively supported by the proposed system.

Switchable UWB pulse generation using a polarization maintaining fiber Bragg grating as frequency discriminator

We propose and successfully demonstrate a novel approach to optically generate ultrawideband (UWB) pulse with switchable shape and polarity by using a polarization-maintaining fiber Bragg grating (PM-FBG) as frequency discriminator. Depending on the shape of the reflective spectrum of the PM-FBG, the system can function as a first- or second-order differentiator for the generation of Gaussian UWB monocycle or doublet pulses. Consequently, the shape and the polarity of the generated UWB pulse can be switched by simple adjustment of a polarization controller (PC). Gaussian monocycle and doublet pulses were successfully obtained with fractional bandwidths of about 188% and 152%, respectively. Higher-order UWB pulses with spectrum covering from 2.9 GHz to 9.8 GHz have also been obtained through adjustment of the PC.

Novel ultra-wideband (UWB) photonic generation through photodetection and cross-absorption modulation in a single electroabsorption modulator

We propose and demonstrate, by proof of concept, a novel method of ultra-wide band (UWB) photonic generation using photodetection and cross-absorption modulation (XAM) of multiple quantum wells (MQW) in a single short-terminated electroabsorption modulator (SEAM). As an optical pump pulse excite the MQWs of SEAM waveguide, the probe light pulse with the same polarity can be generated through XAM, simultaneously creating photocurrent pulse propagating along the waveguide. Using the short termination of SEAM accompanied by the delayed microwave line, the photocurrent pulse can be reversed in polarity and re-modulated the waveguide, forming a monocycle UWB optical pulse. An 89 ps cycle of monocycle pulse with 114% fractional bandwidth is obtained, where the electrical power spectrum centered at 4 GHz of frequency ranges from 0.1 GHz to 8 GHz for -10 dB drops. Meanwhile, the generation processing is also confirmed by observing the same cycle of monocycle electrical pulse from the photodetection of SEAM. The whole optical processing is performed inside a compact semiconductor device, suggesting the optoelectronic integration template has a potential for the application of UWB photonic generation.

All-Optical Ultrawideband Monocycle Generation Using Quadratic Nonlinear Interaction Seeded by Dark Pulses

We propose and demonstrate a new approach to all-optical generation of ultrawideband (UWB) monocycle pulses using the quadratic nonlinear interaction seeded by dark pulses in a periodically poled lithium niobate (PPLN) waveguide. When feeding two dark optical pulses with proper relative time delay to participate in the sum-frequency generation (SFG) in a PPLN, the parametric depletion effect accomplishes the tailoring of the dark pulse to be a UWB monocycle pulse at a single wavelength. Pairs of polarity-inverted UWB monocycle pulses are generated in the experiment with the central wavelength, 10-dB bandwidth, and fractional bandwidth conforming to the UWB definition by the U.S. Federal Communications Commission (FCC, part 15).

Photonic generation of UWB pulses with pulse position modulation

A novel photonic approach to generating ultra-wideband (UWB) signals with pulse position modulation (PPM) is proposed. The proposed system consists of two subsystems, the first subsystem being a two-tap photonic microwave delay-line filter for UWB monocycle pulse generation, the second subsystem being a pulse-position-modulation module to achieve PPM. When a Gaussian pulse train is inputted to the first subsystem, a monocycle pulse train is generated. The PPM is then realised in the second subsystem by modulating the state of polarisation of the monocycle pulse train with a data sequence, which is then sent to a polarisation-dependent device to introduce a time delay difference. An UWB signal with PPM at a bit rate of 625 Mbit/s is experimentally generated.

UWB-over-Fiber transmission system using a dual-output Mach-Zehnder modulator

A novel scheme for ultra-wideband (UWB) monocycle pulse generation is proposed based on a dual-output push-pull Mach-Zehnder modulator (MZM). The MZM is driven by a non-return-to-zero (NRZ) data sequence and biased at the nonlinear point to generate edge-triggered pulses. To combine the complementary pulses forming a monocycle UWB pulse, two schemes are used to implement incoherent summation structure. A proof-of-concept experiment of UWB-over-fiber down-link system is set up. Further, by using digital signal processing (DSP) to calculate the bit error rate (BER), the transmission performance of two system configurations is studied.

Filter-Free Optically Switchable and Tunable Ultrawideband Monocycle Generation Based on Wavelength Conversion and Fiber Dispersion

In this letter, a novel filter-free scheme for all-optical ultrawideband monocycle generation based on wavelength conversion in semiconductor optical amplifier and group-velocity dispersion in single-mode fiber is proposed and experimentally demonstrated. The system is optically switchable in pulse polarity, and tunable in both pulsewidth and radio-frequency spectrum.

Photonic generation of ultrawideband signals using a delay interferometer

We demonstrate a novel scheme to generate ultrawideband (UWB) monocycle and doublet pulses by inputting a dark return-to-zero (RZ) signal into a delay interferometer (DI), which accords with the general features in future applied UWB system, namely, single optical source input, simple configuration and passive device. The two polarized interferential beams have a time delay and a phase difference when they propagate through the DI. By adjusting polarization controllers (PCs), the total phase difference, i.e., the sum of the relative opticalphase difference between two orthogonally polarized components caused by PCs and the optical-phase shift due to birefringence of the polarization-maintaining fiber (PMF), the orientation angle of the polarization beam-splitter (PBS) relative to the two axes of the PMF are able to be changed and controlled. When the appropriate conditions are met, UWB monocycle and doublet pulses are generated conveniently.

On-chip photonic generation of ultra-wideband monocycle pulses

Proposed and experimentally demonstrated is photonic generation of ultra-wideband (UWB) monocycle pulses using a silicon microring resonator to perform phase-modulation-to-intensity-modulation conversion. The microring resonator features compact size and thus is cost-effective especially for applications in UWB communication systems that support multiple users. As a microring resonator with a pin diode can function as a modulator, the use of the microring resonator to realise bi-phase modulation is discussed.

Ultrawideband pulse generation and bipolar coding based on optical cross-polarization modulation in highly nonlinear photonic crystal fiber

A novel optical method for ultrawideband (UWB) monocycle pulse generation and bipolar coding is proposed and experimentally demonstrated. The proposed scheme is based on the cross-polarization modulation effect in highly nonlinear photonic crystal fiber (HNPCF). The monocycle pulse with a time duration of 84 ps is generated, and four groups of bipolar codes are obtained.

Polarity- and Shape-Switchable UWB Pulse Generation Based on a Photonic Microwave Delay-Line Filter With a Negative Tap Coefficient

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> A novel and simple scheme to implement a two- or three-tap photonic microwave filter with one negative coefficient for polarity- and shape-switchable ultrawideband (UWB) pulse generation is proposed and demonstrated. The entire system can be reconfigured as a two- or three-tap microwave delay-line filter with one negative coefficient realized by operating a balanced photodetector (BPD) as a single photodetector or a BPD for the generation of UWB monocycle or doublet pulses. The polarity of the generated UWB pulses can be switched by tuning the transmission axis of the arbitrary wave plate. The proposed scheme is experimentally demonstrated. Gaussian monocycle and doublet pulses with fractional bandwidths of about 174% and 141% are generated. </para>

Simultaneous Optical Spectral Shaping and Wavelength-to-Time Mapping for Photonic Microwave Arbitrary Waveform Generation

Photonic microwave arbitrary waveform generation (AWG) based on simultaneous optical spectral shaping and wavelength-to-time mapping in a single specially designed linearly chirped fiber Bragg grating (LCFBG) is proposed. In the proposed approach, the spectrum of a transform-limited ultrashort optical pulse is spectrally shaped, and at the same time is wavelength-to-time mapped by the LCFBG to generate a microwave pulse with a shape identical to that of the shaped optical spectrum. By designing the LCFBG to have an arbitrary reflection profile, a microwave arbitrary waveform is generated. A simple and effective technique to synthesize the LCFBG with an arbitrary reflection response is proposed. Since amplitude-only index modulation is required, the designed LCFBG can be easily fabricated. Two examples showing the generations of a chirped microwave pulse and an ultra-wideband monocycle pulse are experimentally demonstrated.

Photonic generation of ultrawideband monocycle and doublet pulses by using a semiconductor-optical-amplifier-based wavelength converter

Photonic generation of ultrawideband (UWB) monocycle and doublet pulses is experimentally demonstrated using a cascaded electroabsorption modulator (EAM) and semiconductor optical amplifier by exploiting a combination of cross-absorption modulation and cross-gain modulation. The polarities and shapes of UWB monocycle and doublet pulses can be simply controlled using an optical time-delay controller and the reverse voltage applied to the EAM. The corresponding measured rf spectra meet the UWB criteria.

Ultra-Wideband Pulse Train Generation Based on Turbo-Switch Structures

A simple configuration is proposed and experimentally demonstrated to generate ultra-wideband (UWB) monocycle pulses based on a turbo-switch structure which consists of two reflective semiconductor optical amplifiers (RSOAs). The first RSOA generates an inversed pulse train of the injected signal through the cross-gain modulation, while the second RSOA introduces an overshoot. The overshoot can be enhanced by properly adjusting the currents applied to both of the two RSOAs, therefore, the UWB monocycle pulse train is successfully obtained. By cascading turbo-switches, the polarity-inversed UWB monocycle pairs and the UWB doublet pulse train are numerically realized.