A decision feedback equalization(DFE)algorithm is proposed by simplifying Volterra structure.The simplification principle and process of the proposed Volterra-based equalization algorithm are presented.With the suppor...A decision feedback equalization(DFE)algorithm is proposed by simplifying Volterra structure.The simplification principle and process of the proposed Volterra-based equalization algorithm are presented.With the support of this algorithm,the signal damage for four-level pulse amplitude modulation signal(PAM-4)is compensated,which is caused by device bandwidth limitation and dispersion during transmission in C-band intensity modulation direct detection(IM-DD)fiber system.Experiments have been carried out to demonstrate that PAM-4 signals can transmit over 2 km in standard single-mode fiber(SSMF)based on a 30 GHz Mach-Zehnder modulator(MZM).The bit error rate(BER)can reach the threshold of hard decision-forward error correction(HD-FEC)(BER=3.8×10-3)and its sensitivity is reduced by 2 d Bm compared with traditional feedforward equalization(FFE).Meanwhile,the algorithm complexity is greatly reduced by 55%,which provides an effective theoretical support for the commercial application of the algorithm.展开更多
A bias-independent inter-modulation method is proposed and demonstrated for measuring low-frequency modulation and bias half-wave voltages of Mach-Zehnder modulators(MZMs).The method consists of simultaneous sinusoida...A bias-independent inter-modulation method is proposed and demonstrated for measuring low-frequency modulation and bias half-wave voltages of Mach-Zehnder modulators(MZMs).The method consists of simultaneous sinusoidal modulation on the modulation and bias ports of the MZM under test.Sinusoidal-modulated sidebands heterodyne with each other and generate the desired inter-modulation products after photodetection,which allows extracting both the modulation depth and half-wave voltage for the modulation and bias ports of the MZM.Our method is independent of bias voltages of the MZM,which can be canceled out by carefully choosing the sinusoidal-modulation frequencies.Moreover,the proposed method enables the low swing voltage for measuring both the modulation depth and half-wave voltage of MZMs.Experiments indicate that the proposed method features the simple setup and high accuracy for low-frequency response measurement ranging from 1 Hz to 1 MHz.展开更多
A tunable frequency-multiplying optoelectronic oscillator(OEO) based on a dual-parallel Mach-Zehnder modulator(DPMZM) is proposed and experimentally demonstrated. In the proposed system, the tunable fundamental microw...A tunable frequency-multiplying optoelectronic oscillator(OEO) based on a dual-parallel Mach-Zehnder modulator(DPMZM) is proposed and experimentally demonstrated. In the proposed system, the tunable fundamental microware signal is generated by a tunable optoelectronic oscillator incorporating a phase-shifted fiber Bragg grating(PS-FBG). By adjusting the DC bias of the DPMZM, the frequency-doubled microwave signal with a tunable frequency range from 11 GHz to 20 GHz and the frequency-quadrupled microwave signal with a tunable frequency range from 22.5 GHz to 26 GHz are generated. The phase noises of the fundamental, frequency-doubled and frequency-quadrupled signals at 10 k Hz offset frequency are-105.9 d Bc/Hz,-103.3 d Bc/Hz and-86.2 d Bc/Hz, respectively.展开更多
Relative rotation between the emitter and receiver could effectively modulate the near-field radiative heat transfer(NFRHT)in anisotropic media.Due to the strong in-plane anisotropy,natural hyperbolic materials can be...Relative rotation between the emitter and receiver could effectively modulate the near-field radiative heat transfer(NFRHT)in anisotropic media.Due to the strong in-plane anisotropy,natural hyperbolic materials can be used to construct near-field radiative modulators with excellent modulation effects.However,in practical applications,natural hyperbolic materials need to be deposited on the substrate,and the influence of substrate on modulation effect has not been studied yet.In this work,we investigate the influence of substrate effect on near-field radiative modulator based onα-MoO_(3).The results show that compared to the situation without a substrate,the presence of both lossless and lossy substrate will reduce the modulation contrast(MC)for different film thicknesses.When the real or imaginary component of the substrate permittivity increases,the mismatch of hyperbolic phonon polaritons(HPPs)weakens,resulting in a reduction in MC.By reducing the real and imaginary components of substrate permittivity,the MC can be significantly improved,reaching 4.64 forε_(s)=3 at t=10 nm.This work indicates that choosing a substrate with a smaller permittivity helps to achieve a better modulation effect,and provides guidance for the application of natural hyperbolic materials in the near-field radiative modulator.展开更多
Background Post-weaned piglets suffer from F18+Escherichia coli(E.coli)infections resulting in post-weaning diar-rhoea or oedema disease.Frequently used management strategies,including colistin and zinc oxide,have con...Background Post-weaned piglets suffer from F18+Escherichia coli(E.coli)infections resulting in post-weaning diar-rhoea or oedema disease.Frequently used management strategies,including colistin and zinc oxide,have contrib-uted to the emergence and spread of antimicrobial resistance.Novel antimicrobials capable of directly interacting with pathogens and modulating the host immune responses are being investigated.Lactoferrin has shown promising results against porcine enterotoxigenic E.coli strains,both in vitro and in vivo.Results We investigated the influence of bovine lactoferrin(bLF)on the microbiome of healthy and infected weaned piglets.Additionally,we assessed whether bLF influenced the immune responses upon Shiga toxin-producing E.coli(STEC)infection.Therefore,2 in vivo trials were conducted:a microbiome trial and a challenge infection trial,using an F18+STEC strain.BLF did not affect theα-andβ-diversity.However,bLF groups showed a higher relative abundance(RA)for the Actinobacteria phylum and the Bifidobacterium genus in the ileal mucosa.When analysing the immune response upon infection,the STEC group exhibited a significant increase in F18-specific IgG serum levels,whereas this response was absent in the bLF group.Conclusion Taken together,the oral administration of bLF did not have a notable impact on theα-andβ-diversity of the gut microbiome in weaned piglets.Nevertheless,it did increase the RA of the Actinobacteria phylum and Bifi-dobacterium genus,which have previously been shown to play an important role in maintaining gut homeostasis.Furthermore,bLF administration during STEC infection resulted in the absence of F18-specific serum IgG responses.展开更多
The primary mirrors of current and future large telescopes always employ a segmented mirror configuration.The small but non-negligible gaps between neighboring segments cause additional diffraction,which restricts the...The primary mirrors of current and future large telescopes always employ a segmented mirror configuration.The small but non-negligible gaps between neighboring segments cause additional diffraction,which restricts the performance of high-contrast coronagraph.To solve this problem,we propose a coronagraph system based on a single liquid crystal spatial light modulator(SLM).This spatial light modulator is used for amplitude apodization,and its feasibility and potential performance are demonstrated using a laboratory setup using the stochastic parallel gradient descent(SPGD)algorithm to control the spatial light modulator,which is based on point spread function(PSF)sensing and evaluation and optimized for maximum contrast in the discovery working area as a merit function.The system delivers a contrast in the order of 10−6,and shows excellent potential to be used in current and future large aperture telescopes,both on the ground and in space.展开更多
A novel approach to generate and distribute ultra-wideband (UWB) pulses in optical domain is investigated. In this proposed scheme, a dual-electrode Mach-Zehnder modulator (DE-MZM) is biased at its quadrature poin...A novel approach to generate and distribute ultra-wideband (UWB) pulses in optical domain is investigated. In this proposed scheme, a dual-electrode Mach-Zehnder modulator (DE-MZM) is biased at its quadrature point so as to realize the linear response. Then the intensity of output optical field can be assumed to the subtraction of two input Gaussian pulses. If the input Gaussian pulses are with the same sharp parameters but different time delays, a quasi-monocycle-waveform UWB signal can be generated. If the input Gaussian pulses are with different amplitudes and full-width at half-maximum (FWHM), a quasi-doublet-waveform UWB signal can be generated. A transmission of the UWB signals through a 25-km single mode fiber is carried out successfully. The results in both temporal and frequency domains are also presented.展开更多
A new technique to generate 40-GHz carrier-suppressed return-to-zero (CSRZ) optical pulse trains using only a 10-GHz dual-parallel Mach-Zehnder modulator (MZM) is presented and experimentally demon- strated. The s...A new technique to generate 40-GHz carrier-suppressed return-to-zero (CSRZ) optical pulse trains using only a 10-GHz dual-parallel Mach-Zehnder modulator (MZM) is presented and experimentally demon- strated. The spectrum of the generated CSRZ pulses is calculated by simulation and compared with conventional MZM-based RZ and CSRZ pulse trains. The experimental results demonstrate that CSRZ pulse trains are obtained, and that the carrier and the unwanted 20-GHz low-frequency component are suppressed by 25 dB. The technique can also be extended to 160-GHz CSRZ pulse generation when 40-GHz展开更多
We propose a 40-Gb/s star 16-ary quadrature amplitude modulation (16-QAM) transmitter using a single dual-drive Mach-Zehnder modulator (DDMZM). This transmitter is demonstrated through experiment and simulation an...We propose a 40-Gb/s star 16-ary quadrature amplitude modulation (16-QAM) transmitter using a single dual-drive Mach-Zehnder modulator (DDMZM). This transmitter is demonstrated through experiment and simulation and shows the advantage of simplicity for implementation. Simulation results indicate that error free performance could be achieved for the generated signal after 80-km standard single-mode fiber (SSMF) transmission with coherent detection scheme.展开更多
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 ...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.展开更多
A novel approach for the implementation of microwave photonic filter with positive and negative coefficients based on an unbalanced Mach-Zehnder modulator(MZM) is proposed.In the proposed filter,a microwave signal to ...A novel approach for the implementation of microwave photonic filter with positive and negative coefficients based on an unbalanced Mach-Zehnder modulator(MZM) is proposed.In the proposed filter,a microwave signal to be filtered is applied to an unbalanced MZM.Thanks to the unbalance between the two arms of the modulator,a π phase shift is obtained by adjusting the wavelength interval between the adjacent wavelengths,which leads to the generation of the positive and negative coefficients.The theoretical fundamentals of the design are described,which show that the required unbalanced MZM in the scheme can be well fabricated by the current technology,and the required other components,including the wavelength multiplexer,are also commercially available devices.An eight-tap microwave photonic filter with positive and negative coefficients is demonstrated.The tunability and reconfigurability of the eight-tap microwave photonic filter are also investigated to verify our approach.展开更多
On the silicon-on-insulator platform, an ultra compact temperature-insensitive modulator based on a cascaded microring assistant Mach-Zehnder interferometer is proposed and demonstrated with numerical simulation. Acco...On the silicon-on-insulator platform, an ultra compact temperature-insensitive modulator based on a cascaded microring assistant Mach-Zehnder interferometer is proposed and demonstrated with numerical simulation. According to the calculated results, the tolerated variation of ambient temperature can be as high as 134 ℃ while the footprint of such a silicon modulator is only 340 μm2.展开更多
In this paper,we propose a novel and flexible 16-quadrature amplitude modulation(16QAM) transmitter based on cascaded dual-parallel Mach-Zehnder modulator(DPMZM) and phase modulator(PM).The proposed transmitter is abl...In this paper,we propose a novel and flexible 16-quadrature amplitude modulation(16QAM) transmitter based on cascaded dual-parallel Mach-Zehnder modulator(DPMZM) and phase modulator(PM).The proposed transmitter is able to generate three types of 16QAM signals:square 16QAM,star 16QAM and four-amplitude-four-phase-16-QAM(FAFP-16QAM).The feasibility of the transmitter is verified through experiment,20-Gb/s eye diagrams of the 16QAM signals are obtained.In order to evaluate the performances of the 16QAM signals,simulations are also conducted using VPI Transmission Maker,clear constellations of 40-Gb/s 16QAM signals are achieved by coherent detection.展开更多
For the nonlinearity distortion problem of Mach-Zehnder modulator(MZM)applied in the on-board microwave photonics system,the situation for two input radio frequency(RF)signals with different frequencies and phases is ...For the nonlinearity distortion problem of Mach-Zehnder modulator(MZM)applied in the on-board microwave photonics system,the situation for two input radio frequency(RF)signals with different frequencies and phases is discussed,and an exact analytical solution is derived with the method of expanding Bessel series and Graf addition theory.According to the analytical expression,the nonlinearity characteristics of the modulator can be precisely predicted,and the system performance can be optimized.The correctness of the analytical solution is approved by simulation results.Analytical results indicate that the nonlinearity distortion is suppressed as the decrease of modulation index,the increase of direct current bias phase shift and phase difference between two input RF signals.When the phase difference equals zero orπand the direct current bias phase shift isπ/2,there are only odd-order distortion terms.When the phase difference equals zero orπand the direct current bias phase shift isπ,there are only even-order distortion terms.展开更多
Optical signaling without a high voltage driver for electric-optic modulation is in high demand to reduce power consumption,packaging complexity,and cost.In this work,we propose and experimentally demonstrate a silico...Optical signaling without a high voltage driver for electric-optic modulation is in high demand to reduce power consumption,packaging complexity,and cost.In this work,we propose and experimentally demonstrate a silicon mode-loop Mach–Zehnder modulator(ML-MZM) with record-high modulation efficiency.We used a mode-loop structure to recycle light twice in the phase shifter.With an L-shaped PN junction,a comparably large overlap between the PN junction and optical modes of both TE0 and TE1 was achieved to lower the driving voltage or decrease the photonic device size.Proof-of-concept high-efficiency modulation with low VπL of 0.37 V · cm was obtained.Subvoltage Vπcan be realized with a millimeter’s length phase shifter by this scheme,which makes the realization of CMOS-compatible driverless modulation highly possible.40 Gb/s signaling with a bit error rate below the 7% forward-error-correction threshold was then demonstrated with the fabricated ML-MZM,indicating great potential for high-speed optical communication.展开更多
The characteristics of a conventional LiNbO3 intensity modulator made up of a Mach-Zehnder(MZ) type annealed proton exchange(APE) waveguide and coplanar waveguide(CPW) modulation electrode are presented. The APE waveg...The characteristics of a conventional LiNbO3 intensity modulator made up of a Mach-Zehnder(MZ) type annealed proton exchange(APE) waveguide and coplanar waveguide(CPW) modulation electrode are presented. The APE waveguide characteristics and their relations with process parameters are analyzed. At the same time, the electrical characteristics of modulation electrode, such as modulation voltage, microwave effective index associated with modulation bandwidth, characteristics impedance, are also investigated in detail.展开更多
An approach for generating optical frequency comb(OFC)with tunable free spectral range(FSR)is proposed.Two Mach-Zehnder modulators(MZMs)driven by phase-shifted sinusoidal signals are cascaded to generate OFC with plen...An approach for generating optical frequency comb(OFC)with tunable free spectral range(FSR)is proposed.Two Mach-Zehnder modulators(MZMs)driven by phase-shifted sinusoidal signals are cascaded to generate OFC with plentiful comb lines and the FSR controlled by the drive frequency.Subsequently,a linearly chirped fiber Bragg grating(LCFBG)and a phase modulator(PM)are used to increase the comb FSR by a particular integer multiple.Therefore,by simultaneously controlling the drive frequency of MZMs,the dispersion amount of the LCFBG and the drive signal of the PM,an OFC with desired FSR can be achieved.展开更多
We report broadband all-fiber optical phase modulation based on the photo-thermal effect in a gas-filled hollow-core fiber.The phase modulation dynamics are studied by multi-physics simulation.A phase modulator is fab...We report broadband all-fiber optical phase modulation based on the photo-thermal effect in a gas-filled hollow-core fiber.The phase modulation dynamics are studied by multi-physics simulation.A phase modulator is fabricated using a 5.6-cm-long anti-resonant hollow-core fiber with pure acetylene filling.It has a half-wave optical power of 289 mW at 100 kHz and an average insertion loss 0.6 dB over a broad wavelength range from 1450 to 1650 nm.The rise and fall time constants are 3.5 and 3.7μs,respectively,2–3 orders of magnitude better than the previously reported microfiber-based photo-thermal phase modulators.The gas-filled hollow-core waveguide configuration is promising for optical phase modulation from ultraviolet to mid-infrared which is challenging to achieve with solid optical fibers.展开更多
基金supported by the China Southern Power Grid Science and Technology Project,Research on 230 MHz Iot Access Architecture for Deep Coverage of Power Edge Services and R&D of Key Communication Devices(No.036000KK52180036).
文摘A decision feedback equalization(DFE)algorithm is proposed by simplifying Volterra structure.The simplification principle and process of the proposed Volterra-based equalization algorithm are presented.With the support of this algorithm,the signal damage for four-level pulse amplitude modulation signal(PAM-4)is compensated,which is caused by device bandwidth limitation and dispersion during transmission in C-band intensity modulation direct detection(IM-DD)fiber system.Experiments have been carried out to demonstrate that PAM-4 signals can transmit over 2 km in standard single-mode fiber(SSMF)based on a 30 GHz Mach-Zehnder modulator(MZM).The bit error rate(BER)can reach the threshold of hard decision-forward error correction(HD-FEC)(BER=3.8×10-3)and its sensitivity is reduced by 2 d Bm compared with traditional feedforward equalization(FFE).Meanwhile,the algorithm complexity is greatly reduced by 55%,which provides an effective theoretical support for the commercial application of the algorithm.
基金supported in part by the National Natural Science Foundation of China(Grant No.61927821)National Key Research and Development Program ofChina(Grant No.2018YFE0201900)Fundamental Research Funds for the Central Universities(Grant No.ZYGX2019Z011).
文摘A bias-independent inter-modulation method is proposed and demonstrated for measuring low-frequency modulation and bias half-wave voltages of Mach-Zehnder modulators(MZMs).The method consists of simultaneous sinusoidal modulation on the modulation and bias ports of the MZM under test.Sinusoidal-modulated sidebands heterodyne with each other and generate the desired inter-modulation products after photodetection,which allows extracting both the modulation depth and half-wave voltage for the modulation and bias ports of the MZM.Our method is independent of bias voltages of the MZM,which can be canceled out by carefully choosing the sinusoidal-modulation frequencies.Moreover,the proposed method enables the low swing voltage for measuring both the modulation depth and half-wave voltage of MZMs.Experiments indicate that the proposed method features the simple setup and high accuracy for low-frequency response measurement ranging from 1 Hz to 1 MHz.
基金supported by the National Key R&D Program of China (No.2018YFB1801003)the National Natural Science Foundation of China (Nos.61525501 and 61827817)+1 种基金the Beijing Natural Science Foundation (No.4192022)the Project of Shandong Province Higher Educational Science and Technology Program (No.J17KA089)。
文摘A tunable frequency-multiplying optoelectronic oscillator(OEO) based on a dual-parallel Mach-Zehnder modulator(DPMZM) is proposed and experimentally demonstrated. In the proposed system, the tunable fundamental microware signal is generated by a tunable optoelectronic oscillator incorporating a phase-shifted fiber Bragg grating(PS-FBG). By adjusting the DC bias of the DPMZM, the frequency-doubled microwave signal with a tunable frequency range from 11 GHz to 20 GHz and the frequency-quadrupled microwave signal with a tunable frequency range from 22.5 GHz to 26 GHz are generated. The phase noises of the fundamental, frequency-doubled and frequency-quadrupled signals at 10 k Hz offset frequency are-105.9 d Bc/Hz,-103.3 d Bc/Hz and-86.2 d Bc/Hz, respectively.
基金Project supported by the National Natural Science Foundation of China (Grant No.52106099)the Natural Science Foundation of Shandong Province of China (Grant No.ZR2022YQ57)the Taishan Scholars Program。
文摘Relative rotation between the emitter and receiver could effectively modulate the near-field radiative heat transfer(NFRHT)in anisotropic media.Due to the strong in-plane anisotropy,natural hyperbolic materials can be used to construct near-field radiative modulators with excellent modulation effects.However,in practical applications,natural hyperbolic materials need to be deposited on the substrate,and the influence of substrate on modulation effect has not been studied yet.In this work,we investigate the influence of substrate effect on near-field radiative modulator based onα-MoO_(3).The results show that compared to the situation without a substrate,the presence of both lossless and lossy substrate will reduce the modulation contrast(MC)for different film thicknesses.When the real or imaginary component of the substrate permittivity increases,the mismatch of hyperbolic phonon polaritons(HPPs)weakens,resulting in a reduction in MC.By reducing the real and imaginary components of substrate permittivity,the MC can be significantly improved,reaching 4.64 forε_(s)=3 at t=10 nm.This work indicates that choosing a substrate with a smaller permittivity helps to achieve a better modulation effect,and provides guidance for the application of natural hyperbolic materials in the near-field radiative modulator.
基金The research that yielded these results,was funded by the Belgian Federal Public Service of Health,Food Chain Safety and Environment through the contract RF 17/6314 LactoPigHealthMatthias Dierick is supported by the Flemish fund for scientific research(FWO3S036319).
文摘Background Post-weaned piglets suffer from F18+Escherichia coli(E.coli)infections resulting in post-weaning diar-rhoea or oedema disease.Frequently used management strategies,including colistin and zinc oxide,have contrib-uted to the emergence and spread of antimicrobial resistance.Novel antimicrobials capable of directly interacting with pathogens and modulating the host immune responses are being investigated.Lactoferrin has shown promising results against porcine enterotoxigenic E.coli strains,both in vitro and in vivo.Results We investigated the influence of bovine lactoferrin(bLF)on the microbiome of healthy and infected weaned piglets.Additionally,we assessed whether bLF influenced the immune responses upon Shiga toxin-producing E.coli(STEC)infection.Therefore,2 in vivo trials were conducted:a microbiome trial and a challenge infection trial,using an F18+STEC strain.BLF did not affect theα-andβ-diversity.However,bLF groups showed a higher relative abundance(RA)for the Actinobacteria phylum and the Bifidobacterium genus in the ileal mucosa.When analysing the immune response upon infection,the STEC group exhibited a significant increase in F18-specific IgG serum levels,whereas this response was absent in the bLF group.Conclusion Taken together,the oral administration of bLF did not have a notable impact on theα-andβ-diversity of the gut microbiome in weaned piglets.Nevertheless,it did increase the RA of the Actinobacteria phylum and Bifi-dobacterium genus,which have previously been shown to play an important role in maintaining gut homeostasis.Furthermore,bLF administration during STEC infection resulted in the absence of F18-specific serum IgG responses.
基金supported by the National Natural Science Foundation of China (U2031210 and 11827804)Science Research from the China Manned Space Project (CMS-CSST-2021-A11 and CMS-CSST-2021-B04).
文摘The primary mirrors of current and future large telescopes always employ a segmented mirror configuration.The small but non-negligible gaps between neighboring segments cause additional diffraction,which restricts the performance of high-contrast coronagraph.To solve this problem,we propose a coronagraph system based on a single liquid crystal spatial light modulator(SLM).This spatial light modulator is used for amplitude apodization,and its feasibility and potential performance are demonstrated using a laboratory setup using the stochastic parallel gradient descent(SPGD)algorithm to control the spatial light modulator,which is based on point spread function(PSF)sensing and evaluation and optimized for maximum contrast in the discovery working area as a merit function.The system delivers a contrast in the order of 10−6,and shows excellent potential to be used in current and future large aperture telescopes,both on the ground and in space.
基金supported by the National Natural Science Foundation of China(No.60771008)the Program for New Century Excellent Talents in University (No.NCET-06-0076)+2 种基金Beijing Natural Science Foundation (No.4082024)the Ph.D.Programs Foundation of Ministry of Education of China(No.200800040002)the Foundation for the Returning Scholars,and Beijing Jiaotong University Foundation(No.2006XM003).
文摘A novel approach to generate and distribute ultra-wideband (UWB) pulses in optical domain is investigated. In this proposed scheme, a dual-electrode Mach-Zehnder modulator (DE-MZM) is biased at its quadrature point so as to realize the linear response. Then the intensity of output optical field can be assumed to the subtraction of two input Gaussian pulses. If the input Gaussian pulses are with the same sharp parameters but different time delays, a quasi-monocycle-waveform UWB signal can be generated. If the input Gaussian pulses are with different amplitudes and full-width at half-maximum (FWHM), a quasi-doublet-waveform UWB signal can be generated. A transmission of the UWB signals through a 25-km single mode fiber is carried out successfully. The results in both temporal and frequency domains are also presented.
基金supported by the National Natural Science Foundation of China (No.60736036)the National "863" Program of China (No.2009AA01Z256)the Beijing Supporting Program (No.YB20091000301)
文摘A new technique to generate 40-GHz carrier-suppressed return-to-zero (CSRZ) optical pulse trains using only a 10-GHz dual-parallel Mach-Zehnder modulator (MZM) is presented and experimentally demon- strated. The spectrum of the generated CSRZ pulses is calculated by simulation and compared with conventional MZM-based RZ and CSRZ pulse trains. The experimental results demonstrate that CSRZ pulse trains are obtained, and that the carrier and the unwanted 20-GHz low-frequency component are suppressed by 25 dB. The technique can also be extended to 160-GHz CSRZ pulse generation when 40-GHz
基金supported by the National "863" Program of China under Grant No. 2006AA01Z255
文摘We propose a 40-Gb/s star 16-ary quadrature amplitude modulation (16-QAM) transmitter using a single dual-drive Mach-Zehnder modulator (DDMZM). This transmitter is demonstrated through experiment and simulation and shows the advantage of simplicity for implementation. Simulation results indicate that error free performance could be achieved for the generated signal after 80-km standard single-mode fiber (SSMF) transmission with coherent detection scheme.
基金supported in part by the National Natural Science Foundation of China(No.60736003)the National"863"Project of China(Nos.2009AA01Z222 and 2007AA01Z256)+1 种基金the National"973"Project of China (No.2006CB302805)the Project iCHIP financed by the Italian Ministry of Foreign Affairs.
文摘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.
基金supported by the National Natural Science Foundation of China(No.60807003)the Beijing Nova Program(No.2008A026)the Program for New Century Excellent Talents in University(No.NCET-09-0209)
文摘A novel approach for the implementation of microwave photonic filter with positive and negative coefficients based on an unbalanced Mach-Zehnder modulator(MZM) is proposed.In the proposed filter,a microwave signal to be filtered is applied to an unbalanced MZM.Thanks to the unbalance between the two arms of the modulator,a π phase shift is obtained by adjusting the wavelength interval between the adjacent wavelengths,which leads to the generation of the positive and negative coefficients.The theoretical fundamentals of the design are described,which show that the required unbalanced MZM in the scheme can be well fabricated by the current technology,and the required other components,including the wavelength multiplexer,are also commercially available devices.An eight-tap microwave photonic filter with positive and negative coefficients is demonstrated.The tunability and reconfigurability of the eight-tap microwave photonic filter are also investigated to verify our approach.
基金Project supported by the National Basic Research Program of China(Grant Nos.2011CBA00608,2011CBA00303,2011CB301803, and 2010CB327405)the National Natural Science Foundation of China(Grant Nos.61036011 and 61036010)the Project of Science and Technology from the Communication Information Security Control Laboratory
文摘On the silicon-on-insulator platform, an ultra compact temperature-insensitive modulator based on a cascaded microring assistant Mach-Zehnder interferometer is proposed and demonstrated with numerical simulation. According to the calculated results, the tolerated variation of ambient temperature can be as high as 134 ℃ while the footprint of such a silicon modulator is only 340 μm2.
基金supported by the National Natural Science Foundation of China (Grant Nos.61077052 and 61125504)the National High-Tech Research & Development Program of China ("863" Program) (Grant No. SS2013AA010502)
文摘In this paper,we propose a novel and flexible 16-quadrature amplitude modulation(16QAM) transmitter based on cascaded dual-parallel Mach-Zehnder modulator(DPMZM) and phase modulator(PM).The proposed transmitter is able to generate three types of 16QAM signals:square 16QAM,star 16QAM and four-amplitude-four-phase-16-QAM(FAFP-16QAM).The feasibility of the transmitter is verified through experiment,20-Gb/s eye diagrams of the 16QAM signals are obtained.In order to evaluate the performances of the 16QAM signals,simulations are also conducted using VPI Transmission Maker,clear constellations of 40-Gb/s 16QAM signals are achieved by coherent detection.
文摘For the nonlinearity distortion problem of Mach-Zehnder modulator(MZM)applied in the on-board microwave photonics system,the situation for two input radio frequency(RF)signals with different frequencies and phases is discussed,and an exact analytical solution is derived with the method of expanding Bessel series and Graf addition theory.According to the analytical expression,the nonlinearity characteristics of the modulator can be precisely predicted,and the system performance can be optimized.The correctness of the analytical solution is approved by simulation results.Analytical results indicate that the nonlinearity distortion is suppressed as the decrease of modulation index,the increase of direct current bias phase shift and phase difference between two input RF signals.When the phase difference equals zero orπand the direct current bias phase shift isπ/2,there are only odd-order distortion terms.When the phase difference equals zero orπand the direct current bias phase shift isπ,there are only even-order distortion terms.
基金National Key Research and Development Program of China (2018YFB1801004)National Natural Science Foundation of China (61875049, 61875124,61935011)The Major Key Project of PCL (PCL2021A14)。
文摘Optical signaling without a high voltage driver for electric-optic modulation is in high demand to reduce power consumption,packaging complexity,and cost.In this work,we propose and experimentally demonstrate a silicon mode-loop Mach–Zehnder modulator(ML-MZM) with record-high modulation efficiency.We used a mode-loop structure to recycle light twice in the phase shifter.With an L-shaped PN junction,a comparably large overlap between the PN junction and optical modes of both TE0 and TE1 was achieved to lower the driving voltage or decrease the photonic device size.Proof-of-concept high-efficiency modulation with low VπL of 0.37 V · cm was obtained.Subvoltage Vπcan be realized with a millimeter’s length phase shifter by this scheme,which makes the realization of CMOS-compatible driverless modulation highly possible.40 Gb/s signaling with a bit error rate below the 7% forward-error-correction threshold was then demonstrated with the fabricated ML-MZM,indicating great potential for high-speed optical communication.
文摘The characteristics of a conventional LiNbO3 intensity modulator made up of a Mach-Zehnder(MZ) type annealed proton exchange(APE) waveguide and coplanar waveguide(CPW) modulation electrode are presented. The APE waveguide characteristics and their relations with process parameters are analyzed. At the same time, the electrical characteristics of modulation electrode, such as modulation voltage, microwave effective index associated with modulation bandwidth, characteristics impedance, are also investigated in detail.
基金supported partially by the National Natural Science Foundation of China(Nos.62101027 and 61775015)the Fundamental Research Funds for the Central Universities(No.2019JBM010)。
文摘An approach for generating optical frequency comb(OFC)with tunable free spectral range(FSR)is proposed.Two Mach-Zehnder modulators(MZMs)driven by phase-shifted sinusoidal signals are cascaded to generate OFC with plentiful comb lines and the FSR controlled by the drive frequency.Subsequently,a linearly chirped fiber Bragg grating(LCFBG)and a phase modulator(PM)are used to increase the comb FSR by a particular integer multiple.Therefore,by simultaneously controlling the drive frequency of MZMs,the dispersion amount of the LCFBG and the drive signal of the PM,an OFC with desired FSR can be achieved.
基金We are grateful for financial supports from the National Key Research and Development Program of China(2019YFB2203904)the National Natural Science Foundation of China(U21A20506,62105122,61827820,62005233)+1 种基金the Shenzhen STIC Funding(RCBS20200714114819032)the Local Innovative and Research Teams Project of Guangdong Pear River Talents Program(2019BT02X105).
文摘We report broadband all-fiber optical phase modulation based on the photo-thermal effect in a gas-filled hollow-core fiber.The phase modulation dynamics are studied by multi-physics simulation.A phase modulator is fabricated using a 5.6-cm-long anti-resonant hollow-core fiber with pure acetylene filling.It has a half-wave optical power of 289 mW at 100 kHz and an average insertion loss 0.6 dB over a broad wavelength range from 1450 to 1650 nm.The rise and fall time constants are 3.5 and 3.7μs,respectively,2–3 orders of magnitude better than the previously reported microfiber-based photo-thermal phase modulators.The gas-filled hollow-core waveguide configuration is promising for optical phase modulation from ultraviolet to mid-infrared which is challenging to achieve with solid optical fibers.