Double-sideband Modulation Research Articles

Cavity Resonance Sensor With Disposable Analyte Container for Point of Care Testing

The use of phononic crystals and resonant structures as sensing platforms paves the way to the development of new biomedical technologies. An acoustic sensor with a resonant cavity and a disposable element was investigated in this paper. The sensor consists of seven layers with high acoustic impedance mismatch. The disposable element used was a glass spectrophotometry cuvette and, during the experimentation, it was filled with different liquid analytes showing characteristic transmission features that could be used as measures to differentiate and identify them. Experimental transmission curves were obtained using an electronic characterization system that uses a double sideband modulation technique to acquire valuable information about the structure being analyzed. Simulations using the 1-D transmission line method were performed to support the experimental realizations. The frequency of maximum transmission has been found to be strongly dependent on the speed of sound of the analyte under test.

Optical vector analysis based on double-sideband modulation and stimulated Brillouin scattering.

A high-resolution and high-accuracy optical vector analysis based on optical double-sideband modulation and stimulated Brillouin scattering is proposed and experimentally demonstrated. Different from the conventional OVA based on optical single-sideband modulation, in which the measurement range is limited by the bandwidth of the microwave and optoelectronic components, and the measurement accuracy is restricted by the high-order sidebands, the proposed technique measures the magnitude and phase responses by making use of both ±1st-order sidebands without spectrum response aliasing. As a result, the measurement range is doubled, and the high-order, sideband-induced errors only appear at specific frequencies that are predictable and removable. A proof-of-concept experiment is carried out. The transmission response of a fiber Bragg grating, in a range of 80GHz, is measured with a resolution of less than 667kHz by using 40GHz microwave components.

Iterative nonlinear ISI cancellation in optical tilted filter-based Nyquist 4-PAM system

Abstract The conventional double sideband (DSB) modulation and direct detection scheme suffers from severer power fading, linear and nonlinear inter-symbol interference (ISI) caused by fiber dispersion and square-law direct detection. The system’s frequency response deteriorates at high frequencies owing to the limited device bandwidth. Moreover, the linear and nonlinear ISI is enhanced induced by the bandwidth limited effect. In this paper, an optical tilted filter is used to mitigate the effect of power fading, and improve the high frequency response of bandwidth limited device in Nyquist 4-ary pulse amplitude modulation (4-PAM) system. Furtherly, iterative technique is introduced to mitigate the nonlinear ISI caused by the combined effects of electrical Nyquist filter, limited device bandwidth, optical tilted filter, dispersion, and square-law photo-detection. Thus, the system’s frequency response is greatly improved and the delivery distance can be extended.

Radio-over-fiber DSB-to-SSB conversion using semiconductor lasers at stable locking dynamics.

In radio-over-fiber systems, optical single-sideband (SSB) modulation signals are preferred to optical double-sideband (DSB) modulation signals for fiber distribution in order to mitigate the microwave power fading effect. However, typically adopted modulation schemes generate DSB signals, making DSB-to-SSB conversion necessary before or after fiber distribution. This study investigates a semiconductor laser at stable locking dynamics for such conversion. The conversion relies solely on the nonlinear dynamical interaction between an input DSB signal and the laser. Only a typical semiconductor laser is therefore required as the key conversion unit, and no pump or probe signal is necessary. The conversion can be achieved for a broad tunable range of microwave frequency up to at least 60 GHz. In addition, the conversion can be carried out even when the microwave frequency, the power of the input DSB signal, or the frequency of the input DSB signal fluctuates over a wide range, leading to high adaptability and stability of the conversion system. After conversion, while the microwave phase quality, such as linewidth and phase noise, is mainly preserved, a bit-error ratio down to 10-9 is achieved for a data rate up to at least 8 Gb/s with a detection sensitivity improvement of more than 1.5 dB.

Optical Pulse Compression Reflectometry Based on Double Sideband Modulation

We propose a novel scheme of optical pulse compression reflectometry (OPCR) based on double sideband modulation (DSBM). Owing to the use of DSBM in the novel scheme, the cost-effectiveness and the stability of the OPCR are essentially enhanced. The working principle and the theoretical analysis are demonstrated. Experiment is conducted to verify that the performance of the DSBM-based OPCR is comparable with that based on single sideband modulation. Large measurement range over 58 km with high spatial resolution of 10 cm is experimentally achieved.

Dynamic Range Improvement for an Analog Photonic Link Using an Integrated Electro-Optic Dual-Polarization Modulator

A novel analog photonic link with enhanced spurious-free dynamic range (SFDR) based on an integrated electro-optic dual-polarization modulator is presented and demonstrated. The dual-polarization modulator, which consists of a polarization beam splitter, a polarization beam combiner, and two z-cut LiNbO 3 MZMs, can achieve complementary intensity modulation along the orthogonal polarization directions with different modulation indexes. By properly adjusting the power relationship of the orthogonal polarization directions, two third-order intermodulation distortions (IMD3) have equal intensity and opposite phase and cancel each other out. Combined with a low-biasing technique to reduce the noise power, the SFDR of the link can be further improved. A theoretical analysis is presented and validated by a simulation. The IMD3 can be suppressed by 30.6 dB, giving an improvement in SFDR of about 22 dB compared with a conventional optical double-sideband modulation link.

Frequency-doubling optoelectronic oscillator based on destructive interference

A frequency-doubling optoelectronic oscillator (OEO) using two cascaded modulators based on destructive interference is proposed and experimentally demonstrated. In the proposed system, we utilize a cascaded modulator including a phase modulator and an intensity modulator, which implements a carrier-suppressed double-sideband modulation based on destructive interference to generate a frequency-doubled microwave signal. Meanwhile, the phase modulator is connected by a chirp fiber Bragg grating in the loop, which forms a microwave photonic filter to select the fundamental frequency signal in the OEO loop. As a result, a frequency-doubled microwave signal at 17.9 and 20.5 GHz is generated, respectively. The phase noises and the long-term stability of the generated microwave signals are also investigated.

General AltBOC Modulation with Adjustable Power Allocation Ratio for GNSS

Alternative Binary Offset Carrier (AltBOC) modulation signal has the constraint of an equal power allocation scheme. Thus, it is not flexible enough to meet different requirements. To solve this problem, we propose a General AltBOC (GAltBOC) modulation. The proposed technique can achieve the same function as AltBOC. Meanwhile, its power allocation ratio can be adjusted when required. The detailed derivation of the GAltBOC modulation is presented, and three representative cases as well as the signal properties are discussed. To further improve the combination efficiency, we develop the Interlacing GAltBOC (IGAltBOC) modulation based on the GAltBOC modulation. The Power Spectrum Density (PSD) and correlation functions of the proposed signals are verified by simulation. The code tracking error and implementation complexities are analysed and compared with existing methods. Results show the proposed signals indeed enhance the flexibility of power allocation ratio with the same level code tracking accuracy. Compared with AltBOC modulation, the proposed signal can reach a higher combination efficiency at the expense of relatively higher implementation complexity. Compared with Asymmetric Constant Envelope Double-sideband (ACED) modulation, the proposed signals have significantly lower complexity of signal generation, which is helpful in simplifying the signal generation in the payload transmitter.

Photonic generation of frequency-quadrupling millimeter-wave signals using polarization property

We propose and analyze a photonic method of generating frequency-quadrupling millimeter-wave signal. This scheme is realized by using a single LiNbO3 intensity modulator (IM) and a Faraday mirror based transverse-electrical and transverse-magnetic mode converter in a Sagnac loop without using an optical filter or an electrical microwave phase shifter. Making use of the intrinsic polarization dependence and the veloc- ity phenomenon of the IM, a special double sideband modulation is implemented, which ensures that the optical carrier can be effectively cancelled employing polarization manipulation. A linear polarizer is used as the polari- zation selection element to choose the second-order sidebands from the modulated light. After beating at the photodiode, a frequency-quadrupled millimeter-wave signal with >30 dB radio frequency spurious suppression ratio is generated. The imperfection of the devices is considered when estimating the system performance.©2015

Tunable optoelectronic oscillator incorporating a carrier phase-shifted double sideband modulation system

A tunable optoelectronic oscillator (OEO) implemented by using a carrier phase-shifted double sideband modulation (CPS-DSB) system consisting of an optical coupler (OC), a Mach–Zehnder modulator (MZM) biased at the minimum transmission point, a polarization beam splitter (PBS), and a tunable optical delay line (TODL) is proposed and experimentally demonstrated. The key device in the system is the CPS-DSB system, which functions in conjunction with a chirped fiber Bragg grating (CFBG) in the loop form a high-Q microwave photonic filter (MPF). Through simply adjusting the TODL, the central frequency of the MPF is shifted and the frequency tunability of the OEO can be realized. A detailed theoretical analysis is provided and the results are confirmed by an experiment. A microwave signal with a frequency-tuning range from 7.24 to 14.05GHz is generated. The phase noise, the long-term stability and the side-mode suppression performance of the generated microwave signal are also investigated.

Optically tunable frequency-sextupling optoelectronic oscillator based on Brillouin gain-loss compensation and carrier phase-shifted double sideband modulation

An optically tunable optoelectronic oscillator that generate millimeter wave signals of sextupling Brillouin frequency shift based on gain-loss compensation technique (GLCT) and carrier phase-shifted double sideband modulation (CPS-DSB) is proposed and theoretically analyzed. The GLCT is exploited to generate a triple Brillioun frequency shift oscillator signal through Brillouin amplification and a π/2 CPS-DSB modulation using a dual parallel Mach–Zehnder modulator are implemented to double the oscillation frequency and finally achieve the sextuple millimeter wave signal. Profit from the wavelength-dependent Brillouin frequency shift at f b , frequency-sextupling signal at 6f b which could be tunable from 52.78500–56.68500 GHz by tuning the wavelength of the laser source is realized in theory.

Multi-service RoF links with colorless upstream transmission based on orthogonal phase-correlated modulation.

We propose and experimentally demonstrate a full-duplex radio-over-fiber (RoF) system with colorless upstream transmission based on orthogonal phase-correlated modulation (OPM). This new OPM scheme, which realized by a polarization rotator (PR) and a single-driver Mach-Zahnder modulator (MZM) at the central office (CO), achieves polarization-orthogonality between the optical carrier (OC) and subcarriers generated by radio frequency (RF) signals. By adjusting a polarization controller (PC) in the remote access units (RAU), different modulation schemes can be flexibly implemented, e.g. double-sideband (DSB) modulation for low RF service and optical carrier suppression (OCS) modulation for millimeter-wave (mm-wave) service. In the meantime, the OC can be reused for the upstream transmission without any filtering and additional PC. A proof-of-concept experiment is conducted to demonstrate the feasibility of proposed scheme, where downstream 800-Mb/s orthogonal frequency division multiplexing (OFDM) signal at 58 GHz as an mm-wave service and 800-Mb/s OFDM signal at 0.3 GHz as a low frequency wireless service, as well as an upstream 1-Gb/s on-off keying (OOK) are simultaneously delivered in a shared architecture. By providing heterogeneous services and colorless upstream transmission, the proposed architecture can be seamlessly integrated in wavelength division multiplexing passive optical network (WDM-PON).

An Analog Photonic Link With Compensation of Dispersion-Induced Power Fading

A simple and low cost analog photonic link with the compensation of dispersion-induced power fading is proposed and demonstrated using a dual-electrode Mach-Zehnder modulator. In the proposed link, the modulator is single-electrode driven to realize a novel double-sideband (DSB) modulation. By adjusting the dc bias of the modulator, the frequency response of a dispersive link can be controlled to compensate the power fading at any working frequency. Experimental results show that the power fading in a conventional DSB modulated link after fiber transmission over 25 and 50 km can be both successfully compensated in the proposed link, and the spurious-free dynamic range at 12 GHz of a link with 25 km of single-mode fiber is improved by 11.6 dB.

Broadband Linearization of Dispersive Delay Line Using a Chirped Fiber Bragg Grating

A design of chirped fiber Bragg gratings (CFBGs) for the compensation of higher order dispersion in dispersive delay lines of microwave photonic (MWP) filters driven by broadband sources is presented. It is shown that the modification of the dispersion slope of a nonlinearly CFBG can compensate for third-order dispersion in relatively broad optical bands, resulting in a linear correspondence between group delay and optical frequency. The concept is demonstrated by use of a custom modification of a commercial, low-ripple CFBG for dispersion compensation in 20 nm of the C-band. This broadband linear dispersive delay line is used to provide shape invariance in both the resonance's amplitude and phase responses of single-passband MWP filters based on double-sideband modulation. The dispersion of the delay line is shown to be tunable in the range -170.0 to -143.3 ps/nm by the addition to the CFBG of different lengths of single-mode fiber, without compromising shape invariance.

Control of the optical carrier to sideband ratio in optical double/single sideband modulation by the phase variation of RF signals

We propose and experimentally demonstrate a novel approach to realize tunable optical carrier-to-sideband ratio (OCSR) by introducing two radiofrequency (RF) signals with phase difference to drive a Mach-Zehnder modulator. Stimulated Brillouin scattering is adopted to remove the undesirable sideband, converting double sideband (DSB) to single sideband (SSB). By altering RF signal phase difference, wide ranges of OCSR from −23 to 44dB and −21 to 44dB are obtained for the DSB and SSB modulation, respectively. The operation frequency bandwidth covers from 5 to 42.3GHz. The optimum OCSR to maximize the output RF power is also presented for the best transmission behavior. The proposed approach will be vital for optimizing the transmission performance by improving modulation efficiency and receiver sensitivity.

Flexible compensation of dispersion-induced power fading for multi-service RoF links based on a phase-coherent orthogonal lightwave generator.

A novel technique to simultaneously compensate dispersion-induced power fading for multi-service radio-over-fiber (RoF) links is proposed. At the central office (CO), a phase-coherent orthogonal lightwave generator (POLG) consisting of a polarization rotator (PR) and a single-driver Mach-Zehnder modulator (MZM) is used. By adjusting a polarization controller (PC) in the base station (BS), the phase difference between the orthogonal polarization carrier and two sidebands can be controlled, and the frequency response can be flexibly shifted for individual radio frequency (RF) service. We experimentally shift the destructive interference to the constructive interference at various frequencies for 25 km and 30 km fiber links. The performances of two services carrying 1 Gb/s on-off keying (OOK) data at 9 GHz and 16.6 GHz over a 30 km fiber in the proposed system show receiver sensitivity improvement of ∼12 dB at the bit error rate (BER) of 10(-3) compared with the conventional double sideband (DSB) modulation case.

Investigation of microwave photonic filter based on multiple longitudinal modes fiber laser source

We theoretically study the transfer function of a finite impulse response microwave photonic filter (FIR-MPF) system using a multi-wavelength fiber laser source by considering multiple longitudinal modes in each wavelength. The full response function with the response from longitudinal mode taps is obtained. We also discussed the influence of the longitudinal mode envelope and mode spacing on the performance of FIR-MPF. The response function of the longitudinal mode taps is fully discussed and the contribution is compared with the response of the carrier suppression factor for double sideband (DSB) modulation. The multiple longitudinal modes structure in the wavelength taps can be utilized to engineer the response of the FIR-MPF such that desirable features such as high side lode suppression ratio can be realized. The analysis provides a guideline for designing incoherent FIR-MPF systems.

Electronic characterisation system for measuring frequency changes in phononic crystals

Requirements for measuring frequency changes in phononic crystals (PnCs) are introduced. A novel electronic characterisation system for measuring those changes based on a high frequency double sideband modulation with suppressed carrier is proposed. The reported results prove its reliability for PnCs measurements.

RF Performance of Single Sideband Modulation Versus Dual Sideband Modulation in a Photonic Link

Single sideband optical modulation can be used in multiple RF photonic link applications. However, single sideband optical modulation is often thought to provide lower RF output power than traditional dual sideband modulation techniques. While true in one specific case, it is not true in all cases. We theoretically and experimentally analyze the RF performance of a photonic link utilizing a Z-cut dual-electrode Mach-Zehnder intensity modulator with a 90° RF hybrid that produces optical single sideband modulation. The single sideband performance is compared to double sideband modulation using the same Mach-Zehnder modulator in either a push-pull configuration using a 180° RF hybrid or a single-arm drive configuration. The optical sideband powers, RF output power and the output intercept power and spur-free dynamic range of the third-order intermodulation nonlinearity are compared both theoretically and experimentally for each of the three cases. The performance of a double sideband modulated link using an X-cut inherently push-pull Mach-Zehnder modulator is also compared theoretically, assuming the same V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">π</sub> and insertion loss as the dual-electrode Mach-Zehnder modulator.

Nonlinearity suppression of Mach–Zehnder modulator based on optical carrier processing in radio-over-fiber links

A highly linear transmitter that consists of a dual-drive Mach–Zehnder modulator (DD-MZM), an optical gain, and an optical phase shifter in radio-over-fiber links is proposed and demonstrated by simulation. The optical carrier is split equally with one part driving the DD-MZM, while the other part remaining unmodulated. By properly adjusting the magnitude and phase shift of unmodulated optical carrier, two kinds of main origins of third-order IMD (IMD3) have equal intensity and opposite phase, and cancel each other out. The comparison of the proposed technique and double-sideband modulation by MZM is presented. Simulation results shown that the spurious-free dynamic range of 125.3 dB Hz2/3 is achieved, which is about 26 dB more than a quadrature biased MZM.