This paper proposes a 32‐tupling frequency millimeter‐wave (MMW) filter‐free system based on four Mach‐Zehnder Modulators (MZM) connected in parallel and cascaded with a simple radio‐fiber (RoF) link ...structure. The four MZMs are all at the maximum transmission point (MATP), and the radio frequency (RF) driving voltage phase difference between MZMs is π /2. The center carrier is suppressed by using an optical attenuator (OATT) and an optical phase shifter (OPS). Two parallel MZMs can generate ±8th order and ±12th order optical sidebands, and the ±4th order optical sidebands can be suppressed by adjusting the modulation index m of the MZM, using cascaded two dual‐parallel MZMS(DPMZM) and the phase difference of the RF signal source is π/4 to generate ±16th order optical sidebands. The theoretical analysis and simulation experiments are performed for the scheme proposed in this paper. The results show that the simulated and theoretical values of the optical sideband suppression ratio (OSSR) for ±16th order optical sideband signals are 60.02 and 59.96 dB, respectively, and the simulated and theoretical values of the RF sideband suppression ratio (RFSSR) for the 32‐tupling MMW signal are 56.34 and 53.94 dB, respectively.
A new scheme utilizing a cascade of four Mach–Zehnder modulators (MZMs) to generate a 32‐fold millimeter wave is proposed. In this paper, the working principle and simulation experiments of this scheme are analyzed, and the optical sideband suppression ratios (OSSR) and RF sideband suppression ratios (RFSSR) are obtained to be 59.96, 60.02, 53.94, and 56.34, respectively.
A novel scheme to generate 32-tupling frequency terahertz waves by four Mach-Zehnder modulators (MZMs) cascaded is proposed. Four MZMs are divided into two groups linked in series and each group ...includes two MZMs connected in parallel. The output of the first group and second group of MZMs are ± 4nth and ± 8nth-order sideband signals, respectively. The 0th-order sideband can be cancelled by adjusting the splitting ratio of coupler; The ± 8th-order sidebands can be suppressed by adjusting the modulation index m of MZMs; The ± 8nth (n＞2) sidebands are negligible because of their very small amplitudes. Then the main components of output signal from the second group MZMs are ± 16th-order sidebands, which can generate 32-tupling frequency terahertz signal on the photodetector. The operation principle and simulation experiment of the proposed scheme is performed, and the optical sideband suppression ratio (OSSR) and radio frequency spurious suppression ratio (RFSSR) are obtained to be 53.7 dB, 53.34 dB and 47.7 dB, 47.39 dB, respectively. Simulation experiment values are very close to theoretical values and this demonstrates the feasibility of our scheme. The effects on the OSSR and RFSSR deviated from their designed values are investigated. When the deviations of modulation index, extinction ratio, DC bias, half-wave voltage, the insertion loss of MZM reach about ± 0.42 %, 82 %, ± 8.4 %, ± 1 %, 0.14 %, respectively, and when the deviations of initial phase of RF and splitting ratio of coupler reach about ± 1.3 % at 45°, ± 1.1 % at 90°, ± 2.27 %, respectively, the RFSSR are ≥ 15 dB, which satisfies the engineering applications
Filterless photonic generation of microwave signals with various frequency multiplication factors via series connected polarization modulators is proposed and demonstrated experimentally. Frequency ...octupling, sextupling, or quadrupling microwave signal can be obtained when the polarization state of the light wave, the modulation indices of the modulators, and the phase of the radio frequency (RF) driving signal are suitably set. The optical sideband suppression ratios and RF spurious suppression ratios of the generated frequency multiplication signals are measured. Besides, the frequency-tunable ability and phase noise are analyzed.
A new method is proposed to generate a 32‐tupling frequency millimeter wave (MMW) with eight Mach–Zehnder modulators (MZMs) connected in parallel. Theoretical analyses and simulation experiments are ...conducted. The optical sideband suppression ratio (OSSR) of the obtained ±16th order optical sidebands are 61.54 dB and 61.42 dB, and the radio frequency spurious suppression ratios (RFSSRs) of the generated 32‐tupling frequency MMW are 55.52 dB and 55.27 dB based on the theoretical analysis and simulation experiments, respectively; these outcomes verified the feasibility of the new method. The main parameters used to affect the stability of the generated signal are the modulation index and extinction ratio of MZM. Their effects on the OSSR and RFSSR of the generated signals are investigated when they deviate from their designed values. Compared with the other proposed methods for the generation of 32‐tupling frequency MMW by MZM, our method has the best spectral purity and stability, and it is expected to have important MMW over fiber applications.
High conversion efficiency between electrical and optical power is highly desirable both for high peak and high average power radiation sources. In this paper we discuss a new mechanism based on ...stimulated superradiant emission in a strongly tapered undulator whereby a prebunched electron beam and focused laser are injected into an undulator with an optimal tapering calculated by dynamically matching the resonant energy variation to the ponderomotive decelerating gradient. The method has the potential to allow the extraction of a large fraction (∼50%) of power from a relativistic electron beam by converting it into coherent narrow-band tunable radiation, and shows a clear path to very high power radiation sources of EUV and hard x-rays for applications such as lithography and single molecule x-ray diffraction. Finally, we discuss a technique using chicane delays to suppress the sideband instability, improving radiation generation efficiencies for interaction lengths many synchrotron wavelengths long.
•Chromatic dispersion causes power fading in mm-wave radio-over-fiber links.•Power fading techniques resulting in OSSB-C signal prove to be most universal.•Simple MRR on a PIC promises competitive ...results in power fading mitigation.•OSSB-C by MRR proves to be an effective solution for carrier distribution in PON of arbitrary topology.•Simple MRR in an integrated RoF transmitter enables power-penalty free transmission.
In this paper we address the limiting effect of power fading (PF) in fiber optic communication links, due to the fiber’s dispersive properties, and suggest a mitigation approach in intensity-modulated radio-over-fiber (RoF) applications. The proposed method is independent of the length of the optical transmission path. PF is mitigated by employing a simple integrated photonic structure, i.e., a single micro-ring resonator. The latter features a periodic notch-filter response, employed to suppress one of the sidebands in an optical double sideband (ODSB) modulation, reducing the PF of the received RF signal. The suppression ratio measured by the optical spectrum analyzer is 24 dB. In this way we succeeded in reducing the RF signal’s power ripple at the receiving end to 3 dB. The proposed approach promises an economic yet effective solution to overcoming the PF in point-to-multipoint-topology optical networks.
A folded half-wavelength microstrip resonator with a stepped impedance structure (FSIR) is designed to extend the second harmonic and affect the strength of the external electromagnetic coupling. The ...FSIRs of electromagnetic mutual cancellation structure and strong electric coupling structures are designed to realize the design of narrowband and broadband filters with extended second harmonic, respectively. A T- junction is designed to cascade the two high-order filters to achieve high isolation between two channels. The duplexer is fabricated on a single piece of 2-in double-sided YBCO (YBa 2 Cu 3 O 7 ) thin film on an MgO substrate with a dimension of 34.86×26.30×0.50 mm 3 , a thickness of 0.5 mm, and a dielectric constant of 9.8. At 77K, the measured central frequency of the duplexer are 910 and 1100 MHz, the fractional bandwidths are 2.19% and 18.18%, the out-of-band rejections are greater than 60 dB, the two second harmonic are located at 2.4 GHz and 2.5 GHz, the insertion loss is less than 0.20 dB, and the return losses are better than 16.1 dB and 17.2 dB. The test results of the duplexer are in good agreement with the simulated ones.
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•A brief review of techniques used for hetero-nuclear broadband decoupling is provided;•Adiabatic decoupling achieves up to 1 MHz wide decoupling bandwidth in liquids ...applications;•Decoupling sideband suppression techniques reduce the artefacts by a factor of >1000;•Perspectives of future developments in adiabatic decoupling are outlined.
It is shown that adiabatic decoupling is extremely flexible and achieves very high figure of merit (decoupling bandwidth to RF amplitude ratio) exceeding that of the conventional composite pulse decoupling (CPD) methods by more than an order of magnitude. This comes at a price of increasingly intrusive cycling sidebands when the decoupling bandwidth exceeds that of the CPD methods. Following a brief review of the decoupling theory and modes of adiabatic sweeps a particular attention is focused on decoupling sideband suppression techniques. The close to perfect inversion profiles of adiabatic pulses ensure by far fewer cyclic sidebands as compared to the typically complex sideband patterns observed in CPD applications. The coherent sideband suppression techniques eliminate the cycling sidebands by altering their phase in successive scans thus achieving sideband reduction levels by up to four orders of magnitude and leaving a clean baseline. We show that adiabatic decoupling is highly adaptive offering significant power savings in spin systems with smaller J-couplings while in the other extreme enabling 13C decoupling of up to a 1 MHz wide bandwidth potentially satisfying the needs of ultra-high-field NMR for the foreseeable future.
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