A method to evaluate the influence of the laser linewidth on the linearly frequency-modulated(LFM)signals generated by heterodyning two free-running laser diodes(LDs)is proposed.The Pearson correlation coefficient bet...A method to evaluate the influence of the laser linewidth on the linearly frequency-modulated(LFM)signals generated by heterodyning two free-running laser diodes(LDs)is proposed.The Pearson correlation coefficient between the instantaneous frequency of the generated LFM signal and that of an ideal LFM signal is introduced to quantify the quality of the generated LFM signal.The closed-form solution of the correlation coefficient is given,which shows that the correlation coefficient is determined by the ratio of the LFM signal bandwidth to the square root of the total linewidth of the two LDs when the observation interval is fixed.Simulation results are also given,which proves the correctness of the theoretical results.展开更多
Jaipur,India,is experiencing rapid urbanization that is significantly altering its land use and land cover(LULC)patterns,presenting both challenges and opportunities for sustainable development and socio-economic adva...Jaipur,India,is experiencing rapid urbanization that is significantly altering its land use and land cover(LULC)patterns,presenting both challenges and opportunities for sustainable development and socio-economic advancement.This study utilizes advanced geospatial and remote sensing technologies to assess these changes and project future scenarios.Specifically,satellite data were processed using Google Earth Engine,land cover was accurately classified using the Random Forest algorithm,and future projections were modeled through QGIS-MOLUSCE using a polynomial-based Cellular Automata–Artificial Neural Network(CA-ANN)approach.Analysis of Landsat imagery for the years 2000 and 2020 reveals a dramatic 188.59%increase in urban built-up areas and a 145.44%rise in vegetation cover,largely due to successful afforestation efforts.Meanwhile,barren land declined by 47.37%,and water bodies exhibited fluctuating trends,reflecting the intricate interplay between urban development and climatic variability.Looking ahead to 2045,model projections estimate that built-up areas will expand to approximately 1303.08 square kilometres,potentially threatening the integrity of vital green spaces and aquatic ecosystems.These findings highlight the urgent need for integrated policy interventions aimed at mitigating environmental risks such as urban heat island effects and biodiversity loss.By providing a detailed account of past and present LULC dynamics,this research delivers actionable,data-driven insights to support sustainable urban planning.Moreover,the integration of urban growth models with climate resilience strategies offers a replicable framework for managing urban expansion in other rapidly developing cities,particularly those situated in semi-arid regions.展开更多
A set of integrated Orthogonal Frequency Division Multiplexing(OFDM) modulation and demodulation system is proposed and its performance is verified in reference to the standard of IEEE802.16a for WMAN.The design,combi...A set of integrated Orthogonal Frequency Division Multiplexing(OFDM) modulation and demodulation system is proposed and its performance is verified in reference to the standard of IEEE802.16a for WMAN.The design,combined with analogy front-end,adopts Texas Instrument(TI) Company's 6701 evaluation module(EVM) to construct digital Intermediate Frequency(IF) platform.A DSP-based baseband processing software module is embedded into the system.The proposed scheme makes it possible for users to select various software modules to set up connections with different throughput performance.Taking into account the given hardware configuration,the design aims to optimize the algorithm modules to accomplish better system performance.展开更多
We comprehensively characterize the transmission performance of m-ary quadrature amplitude modulation(m-QAM) signals through a silicon microring resonator in the experiment. Using orthogonal frequency-division multipl...We comprehensively characterize the transmission performance of m-ary quadrature amplitude modulation(m-QAM) signals through a silicon microring resonator in the experiment. Using orthogonal frequency-division multiplexing based on offset QAM(OFDM/OQAM) which is modulated with m-QAM modulations, we demonstrate low-penalty data transmission of OFDM/OQAM 64-QAM, 128-QAM, 256-QAM, and 512-QAM signals in a silicon microring resonator. The observed optical signal-to-noise ratio(OSNR) penalties are 1.7 dB for 64-QAM,1.7 dB for 128-QAM, and 3.1 dB for 256-QAM at a bit-error rate(BER) of 2 × 10^(-3) and 3.3 dB for 512-QAM at a BER of 2 × 10^(-2). The performance degradation due to the wavelength detuning from the microring resonance is evaluated, showing a wavelength range of ~0.48 nm with BER below 2 × 10^(-3). Moreover, we demonstrate data transmission of 191.2-Gbit/s simultaneous eight wavelength channel OFDM/OQAM 256-QAM signals in a silicon microring resonator, achieving OSNR penalties less than 2 dB at a BER of 2 × 10^(-2).展开更多
基金supported by the National Key R&D Program of China(No.2017YFE0121500)the National Natural Science Foundation of China(Nos.61971193 and 61601297)+1 种基金the Open Fund of State Key Laboratory of Advanced Optical Communication Systems and Networks,Peking University,China(No.2020GZKF005)the Fundamental Research Funds for the Central Universities。
文摘A method to evaluate the influence of the laser linewidth on the linearly frequency-modulated(LFM)signals generated by heterodyning two free-running laser diodes(LDs)is proposed.The Pearson correlation coefficient between the instantaneous frequency of the generated LFM signal and that of an ideal LFM signal is introduced to quantify the quality of the generated LFM signal.The closed-form solution of the correlation coefficient is given,which shows that the correlation coefficient is determined by the ratio of the LFM signal bandwidth to the square root of the total linewidth of the two LDs when the observation interval is fixed.Simulation results are also given,which proves the correctness of the theoretical results.
文摘Jaipur,India,is experiencing rapid urbanization that is significantly altering its land use and land cover(LULC)patterns,presenting both challenges and opportunities for sustainable development and socio-economic advancement.This study utilizes advanced geospatial and remote sensing technologies to assess these changes and project future scenarios.Specifically,satellite data were processed using Google Earth Engine,land cover was accurately classified using the Random Forest algorithm,and future projections were modeled through QGIS-MOLUSCE using a polynomial-based Cellular Automata–Artificial Neural Network(CA-ANN)approach.Analysis of Landsat imagery for the years 2000 and 2020 reveals a dramatic 188.59%increase in urban built-up areas and a 145.44%rise in vegetation cover,largely due to successful afforestation efforts.Meanwhile,barren land declined by 47.37%,and water bodies exhibited fluctuating trends,reflecting the intricate interplay between urban development and climatic variability.Looking ahead to 2045,model projections estimate that built-up areas will expand to approximately 1303.08 square kilometres,potentially threatening the integrity of vital green spaces and aquatic ecosystems.These findings highlight the urgent need for integrated policy interventions aimed at mitigating environmental risks such as urban heat island effects and biodiversity loss.By providing a detailed account of past and present LULC dynamics,this research delivers actionable,data-driven insights to support sustainable urban planning.Moreover,the integration of urban growth models with climate resilience strategies offers a replicable framework for managing urban expansion in other rapidly developing cities,particularly those situated in semi-arid regions.
文摘A set of integrated Orthogonal Frequency Division Multiplexing(OFDM) modulation and demodulation system is proposed and its performance is verified in reference to the standard of IEEE802.16a for WMAN.The design,combined with analogy front-end,adopts Texas Instrument(TI) Company's 6701 evaluation module(EVM) to construct digital Intermediate Frequency(IF) platform.A DSP-based baseband processing software module is embedded into the system.The proposed scheme makes it possible for users to select various software modules to set up connections with different throughput performance.Taking into account the given hardware configuration,the design aims to optimize the algorithm modules to accomplish better system performance.
基金National Program for Support of Top-Notch Young ProfessionalsNational Natural Science Foundation of China(NSFC)(11574001,11274131,61222502)Program for New Century Excellent Talents in University(NCET)(NCET-11-0182)
文摘We comprehensively characterize the transmission performance of m-ary quadrature amplitude modulation(m-QAM) signals through a silicon microring resonator in the experiment. Using orthogonal frequency-division multiplexing based on offset QAM(OFDM/OQAM) which is modulated with m-QAM modulations, we demonstrate low-penalty data transmission of OFDM/OQAM 64-QAM, 128-QAM, 256-QAM, and 512-QAM signals in a silicon microring resonator. The observed optical signal-to-noise ratio(OSNR) penalties are 1.7 dB for 64-QAM,1.7 dB for 128-QAM, and 3.1 dB for 256-QAM at a bit-error rate(BER) of 2 × 10^(-3) and 3.3 dB for 512-QAM at a BER of 2 × 10^(-2). The performance degradation due to the wavelength detuning from the microring resonance is evaluated, showing a wavelength range of ~0.48 nm with BER below 2 × 10^(-3). Moreover, we demonstrate data transmission of 191.2-Gbit/s simultaneous eight wavelength channel OFDM/OQAM 256-QAM signals in a silicon microring resonator, achieving OSNR penalties less than 2 dB at a BER of 2 × 10^(-2).
