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Dual Parallel Multi-electrode Traveling Wave Mach-Zehnder Modulator for 200 Gb/s Intra-datacenter Optical Interconnects
摘要： We present a silicon photonic dual parallel multi-electrode Mach-Zehnder modulator (MEMZM) based transmitter targeting 200 Gb/s 4-level pulse amplitude modulation (PAM4) short reach transceivers. The MEMZMs have an average Vπ and electro-optic (EO) bandwidth of 5 V and 38 GHz, respectively. The transmitter is characterized versus receiver equalizer taps, received signal power, driving voltage swing, crosstalk voltage swing, bitrate, and reach. Results reveal that using only a 3-tap equalizer at the receiver, 100 Gb/s PAM4 net rate per lane can be achieved at a bit error rate (BER) below the KP4 forward error correction (KP4-FEC) threshold of 2.4 × 10?4. Moreover, up to 128 Gb/s can be received at a BER below the KP4-FEC threshold using only 2 Vpp and 1 Vpp driving the MEMZM segments. Then, both MEMZMs are driven simultaneously to assess the crosstalk impact on the BER performance at parallel operation. Driven by four binary signals, we demonstrate 200 Gb/s PAM4 transmission over up to 10 km of single mode fiber at a BER below the KP4-FEC threshold.
关键词： Optical interconnects,Fiber optics systems,silicon nanophotonics,Electro-optical systems
更新于2025-09-23 15:22:29
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Characterization of Polarization Pulling in Fiber Optical Parametric Amplifiers
摘要： In fiber optical parametric amplifiers (FOPAs), the output states of polarization (SOPs) of both the signal and the idler are affected by the pump SOP through the polarization pulling effect. We proposed a normalized model to characterize the general dynamics of polarization pulling in degenerated pump FOPAs. By using this model, we determined the relationship between the output degree of polarization (DOP) and the gain of the FOPAs over three orders of magnitude changes in polarization-mode dispersion (PMD) coefficient. We demonstrated numerically that when fibers with typical PMD coefficients are used, the output signals of the FOPAs can achieve higher DOP than those of co-propagating fiber Raman amplifiers, which depends on whether the parametric gain is sufficiently large to compensate the PMD-induced phase mismatch. We also found that for FOPAs using different types of fibers with moderate PMD coefficients, this DOP-gain relationship exhibits highly similar behaviors. We thus adopted a set of modified empirical formulas to analyze this relationship. This formula can also describe the relationship between the output DOP and the conversion efficiency of the idler. The results indicate that in all cases studied, FOPAs achieve much stronger polarization pulling to the idlers than the signals.
关键词： Nonlinear optics,parametric oscillators and amplifiers,polarization-selective devices
更新于2025-09-23 15:22:29
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All-fiberized top-hat beam shaper by mode content control and multimode interference suppression
摘要： A new method of all-fiberized top-hat beam shaper based on controlling mode content and suppressing multimode interference is proposed both numerically and experimentally. The sample is fabricated by fusion splicing a predetermined tapered multimode fiber to a nearly single mode fiber. A 2D simulation model to calculate the mode content weight with different taper ratio and taper shape is established, and the output intensity profile in multimode fiber is investigated. Based on the simulation results, we fabricated an all-fiberized beam shaper, achieving a top-hat beam at a taper ratio of 0.51 with parabolic taper shape. The flatness factor of the top-hat beam is measured to be about 0.6. Theoretical results show a good agreement with the experiment results.
关键词： optical fiber devices,beam shaper,Fiber optics,laser beams
更新于2025-09-23 15:22:29
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Frequency Extension of Atomic Measurement of Microwave Strength Using Zeeman Effect
摘要： Measuring the field strength of an electromagnetic wave based on atomic quantum mechanics is expected to be an innovative method to realize stable and reliable measurements. However, the major issue of atomic measurements is that the measurable frequency is limited to the resonant frequency of atoms. Therefore, in this paper, we demonstrate the measurement at arbitrary frequencies using the Zeeman effect in a static magnetic field. A cesium vapor cell is placed in a static magnetic field of approximately 40 mT, which causes the resonant frequency of the cesium atom to shift from 9.2 to 8.2 GHz. In addition, the Rabi frequency due to the interaction between cesium atoms and microwaves is measured at the frequency of 8.2 GHz in this experiment.
关键词： frequency measurement,microwave measurements,metrology,microwave spectroscopy,electromagnetic measurements,Atom optics,atomic measurements,measurement standards
更新于2025-09-23 15:22:29
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Generation of optical signal and terahertz idler photons by spontaneous parametric down-conversion
摘要： Frequency-angular characteristics of signal and idler photons generated under spontaneous parametric down-conversion are studied in a strongly frequency nondegenerate regime, without paraxial approximation, accounting for possible inherent absorption of idler waves in a nonlinear crystal, classical thermal field fluctuations, and the multimode character of parametric interaction induced by transverse spatial limitation of the pump beam. Spatial limitation is shown to lead to a huge increase in angular divergence of the idler photons generated at terahertz frequencies. General expressions are obtained for the frequency-angular sensitivity function of the nonlinear-optical terahertz wave detector and for power densities of the signal and idler photon fluxes. The absorption-induced difference in the parametric conversion coefficients for the noise and externally incident radiation of the idler frequency is shown to be described by approximately the same loss factor for all active spatial idler modes. Two different parametric contributions of the internal thermal noise to the number of output idler photons were revealed with different dependence on the idler-wave absorption. Expressions for the loss factors, which describe absorption-induced effects in signal and idler channels, are obtained and shown to be turning into one another by changing the sign of the absorption coefficient. Relative contribution of thermal and quantum field fluctuations into the intrinsic radiation of a nonlinear crystal at signal and idler frequencies is analyzed accounting for the crystal absorption properties.
关键词： nonlinear optics,thermal fluctuations,terahertz,quantum fluctuations,absorption,spontaneous parametric down-conversion
更新于2025-09-23 15:22:29
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Ultra-broadband second harmonic generation in ZnO nano-tetrapod with over-one-octave bandwidth
摘要： Broadband nonlinear optical frequency conversion has attracted considerable interest in many applications such as optical communication, frequency comb generation and so on. Here, we report on the ultra-broadband second harmonic generation (SHG) from the Zinc oxide nano-tetrapod with less stringent phase-matching requirement. Using a super-continuum source together with an optical parametric oscillator as the excitation light, a broadband SHG with over-one-octave bandwidth spanning from the ultraviolet to near-infrared (375-1100 nm) is readily obtained. The SHG dependence of pump polarization and pump power is also characterized systematically. This nanoscale ultra-broadband optical converter may open a new way for various applications ranging from imaging to on-chip all-optical signal processing operations.
关键词： Nonlinear optics,Nanostructured materials
更新于2025-09-23 15:22:29
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Additional Nonreciprocity Effects in the Magneto-Optics of Asymmetric Layer Structures
摘要： It has been shown that space–time inversion symmetry breaking at the normal incidence of a quasiplane wave on an asymmetric multilayer structure in the Voigt geometry can result in the formation of the angular Goos–H?nchen effect at reflection and transmission, as well as the spatial Goos–H?nchen effect at transmission. The effects are characterized by nonreciprocity not only with respect to the inversion of direction of static magnetic field but also with respect to the permutation of nongyrotropic layers surrounding a gyrotropic layer.
关键词： asymmetric layer structures,nonreciprocity,Voigt geometry,magneto-optics,Goos–H?nchen effect
更新于2025-09-23 15:22:29
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Donor Impurity States in Semiconductor Zincblende Nitride Quantum Systems as a Source of Nonlinear Optical Response
摘要： The optical absorption and the optical rectification coefficients associated to hydrogenic impurity interstate transitions in zincblende GaN-based nanostructures of the quantum wire type are investigated. The system is assumed to have cylindrical shape and the influence of external tuning probes such as hydrostatic pressure and static electric fields is particularly taken into account. The electron states are obtained within the effective mass approximation, via the exact diagonalization of the donor-impurity Hamiltonian with parabolic confinement. The nonlinear optical coefficients are calculated using a nonperturbative solution of the density-matrix Bloch equation. Our results show that the resonance-related features of the optical response become shifted in the frequency range of the incident radiation due to the effect of the hydrostatic pressure, the strength of the applied field and the change in the impurity center position.
关键词： Quantum Wire,Nonlinear Optics,Hydrostatic Pressure,Zincblende GaN
更新于2025-09-23 15:22:29
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Scalable compact mode (de)multiplexer based on asymmetric Y-junctions
摘要： A scalable asymmetric Y-junctions waveguide mode (de)multiplexer ((de)MUX) is theoretically proposed. The high-order mode in the stem is designed to be separated from the lower-order mode and evolves into the fundamental mode in the narrow arm, through waveguide widths optimization by effective index matching and beam propagation method. Within the wavelength range from 1450 to 1630 nm, the four modes (de)MUX with small footprint of 23 × 3.2 μm2 demonstrates the insertion loss and crosstalk of less than 0.14 dB and -16 dB, respectively. This scheme may be expanded to handle more modes in (de)MUX design.
关键词： Waveguides,Integrated optics devices,Modes,Multiplexing
更新于2025-09-23 15:22:29
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[IEEE 2018 International Carnahan Conference on Security Technology (ICCST) - Montreal, QC, Canada (2018.10.22-2018.10.25)] 2018 International Carnahan Conference on Security Technology (ICCST) - Reliable Leak Detection in Pipelines Using Integrated DdTS Temperature and DAS Acoustic Fiber-Optic Sensor
摘要： Reliable and early detection of leaks in pipelines transporting liquid or gas is highly desirable. In this work, two orthogonal technologies based on high-sensitivity fiber-optic distributed sensing were integrated into one system and tested for their effectiveness in actual field installations. The first technology is based on temperature difference detection using Distributed Differential Temperature Sensor (DdTS or DDTS). The second is based on Distributed Acoustic Sensor (DAS), which uses Coherent Optical Time-Domain Reflectometry (C-OTDR). DdTS can almost instantaneously detect a temperature difference in the optical fiber as low as 0.0005 οC, while C-OTDR can detect minute wide-bandwidth acoustic signals. Both technologies can detect the location of a leak to within a few meters. Experimental results for water and nitrogen gas leaks detected by the integrated system are presented for two different installations in the field – one where the cable was buried directly in the soil and another where the cable was buried in soil inside a 2” conduit for about 29 km. DdTS reliably detected leaks at both installations, while DAS detected leaks only when the cable was buried directly in soil. Test results show that the integration of both DdTS and DAS technologies can increase the probability of leak detection and minimize false/nuisance alarms. The integrated system also detected third party interference (TPI), thus providing a one-system solution for pipeline integrity monitoring and intrusion detection up to 40 km from a central location.
关键词： Oil and Gas Pipeline,DdTS,Leak Detection,Fiber Optics Sensor,DTS,TPI,DAS,C-OTDR
更新于2025-09-23 15:22:29