In the present work we model the global ionospheric total electron content (TEC) with the analysis of empirical orthogonal functions (EOF). The obtained statistical eigen modes, which makeup the modeled TEC, consist o...In the present work we model the global ionospheric total electron content (TEC) with the analysis of empirical orthogonal functions (EOF). The obtained statistical eigen modes, which makeup the modeled TEC, consist of two factors: the eigen vectors mapping TEC patterns at latitude and longitude (or local time LT), and the corresponding coefficients displaying the TEC variations in different time scales, i.e., the solar cycle, the yearly (annual and semiannual) and the diurnal universal time variations. It is found that the EOF analysis can separate the TEC variations into chief processes and the first two modes illustrate the most of the ionospheric climate properties. The first mode contains both the semiannual component which shows the semiannual ionospheric anomaly and the annual component which shows the annual or non-seasonal ionospheric anomaly. The second mode contains mainly the annual component and shows the normal seasonal ionospheric variation at most latitudes and local time sectors. The annual component in the second mode also manifests seasonal anomaly of the ionosphere at higher mid-latitudes around noontime. It is concluded that the EOF analysis, as a statistical eigen mode method, is resultful in analyzing the ionospheric climatology hence can be used to construct the empirical model for the ionospheric climatology.展开更多
An algorithm is presented for raising an approximation order of any given orthogonal multiscaling function with the dilation factor a. Let φ(x) = [φ1(x),φ2(x),…,φr(x)]T be an orthogonal multiscaling function with...An algorithm is presented for raising an approximation order of any given orthogonal multiscaling function with the dilation factor a. Let φ(x) = [φ1(x),φ2(x),…,φr(x)]T be an orthogonal multiscaling function with the dilation factor a and the approximation order m. We can construct a new orthogonal multiscaling function φnew(x) = [ φT(x). f3r+1(x),φr+2(x),…,φr+s(x)}T with the approximation order m + L(L ∈ Z+). In other words, we raise the approximation order of multiscaling function φ(x) by increasing its multiplicity. In addition, we discuss an especial setting. That is, if given an orthogonal multiscaling function φ(x) = [φ1 (x), φ2(x), …, φr(x)]T is symmetric, then the new orthogonal multiscaling function φnew(x) not only raise the approximation order but also preserve symmetry. Finally, some examples are given.展开更多
A novel scheme to generate, transmit, and receive an optical orthogonal frequency division multiplexing （OFDM） continuous phase modulation （CPM） signal, which is combining minimum shift keying （MSK） coding with ...A novel scheme to generate, transmit, and receive an optical orthogonal frequency division multiplexing （OFDM） continuous phase modulation （CPM） signal, which is combining minimum shift keying （MSK） coding with OFDM optical modulation, for downlink application in a 4×2.5-Gb/s wavelength division multiplexing （WDM） passive optical access network, is proposed and experimentally validated. We also realize wavelength remodulation for carrying upstream on-off keying （OOK） data to reduce the cost budget at the optical network unit. The experimental results show that the power penalties for the downlink and the uplink data after transmission over 25-km SMF-28 fiber are 0.1 dB and smaller than 0.4 dB, respectively.展开更多
We propose a novel and simple all-optical 160-Gb/s orthogonal frequency division multiplexing（OFDM） symbol generator which is based on discrete triangle waveform driving-LiNbO_3 modulators to realize large-range lin...We propose a novel and simple all-optical 160-Gb/s orthogonal frequency division multiplexing（OFDM） symbol generator which is based on discrete triangle waveform driving-LiNbO_3 modulators to realize large-range linear optical shift.The entire system needs 64 discrete modulators：at the transmitter,a 2.5-Gb/s optical duobinary（ODB） modulator for data modulation and a 2.5-Gb/s triangle waveform driving-LiNbO_3 phase modulator for phase shift to generate each subcarrier;and at the receiver,a 2.5-GHz optical band pass filter（OBPF） using Faraday anomalous dispersion optical effect to separate them.Excellent bit error rate（BER） is observed after 1060 km of transmission without any dispersion compensation.展开更多
We study an electronic compensator （EC） as a receiver for a 100-Gb/s polarization division multiplexing coherent optical orthogonal frequency division multiplexing （PDM-CO-OFDM） system without optical dispersion c...We study an electronic compensator （EC） as a receiver for a 100-Gb/s polarization division multiplexing coherent optical orthogonal frequency division multiplexing （PDM-CO-OFDM） system without optical dispersion compensation.EC,including electrical dispersion compensation （EDC）,least squares channel estimation and compensation （LSCEC）,and phase compensation （PC）,is used to compensate for chromatic dispersion （CD）,phase noise,polarization mode dispersion （PMD）,and channel impairments,respectively.Simulations show that EC is highly effective in compensating for those impairments and that the performance is close to the theoretical limitation of optical signal-to-noise rate （OSNR）,CD,and PMD.Its robustness against those transmission impairments and fiber nonlinearity are also systematically studied.展开更多
Phase pre-emphasis is theoretically studied and introduced to reduce peak-to-average power ratio （PAPR） in optical orthogonal frequency division multiplexing （OFDM） systems. In intensity modulated （IM） systems, ...Phase pre-emphasis is theoretically studied and introduced to reduce peak-to-average power ratio （PAPR） in optical orthogonal frequency division multiplexing （OFDM） systems. In intensity modulated （IM） systems, simulations show noticeable PAPR reductions： 4.14 dB （N = 16） and 15.48 dB （N = 512） in time lens-based OFDM, N is the number of subcarriers. An equation is developed to calculate phase values and is proved to be effective. Optical implementing methods are proposed and analyzed. In a time lens-based OFDM system, phase pre-emphasis reduces fiber nonlinearity and results in a 5.2-dB increase of launch power at the bit error rate （BER） of 10 ？6 . Simulations also show similar PAPR reduction and fiber nonlinearity mitigation in optical inverse discrete Fourier transformer （OIDFT） based OFDM systems.展开更多
基金supported by the Special Fund for State Seismology Bureau (Grant No. 201008007)the KIP Pilot Project of CAS (Grant No. YYYT-1110-02)+1 种基金the National Natural Science Foundation of China (Grant Nos. 40974090, 41131066)the National Basic Research Program of China ("973" Project) (Grant No. 2011CB811405)
文摘In the present work we model the global ionospheric total electron content (TEC) with the analysis of empirical orthogonal functions (EOF). The obtained statistical eigen modes, which makeup the modeled TEC, consist of two factors: the eigen vectors mapping TEC patterns at latitude and longitude (or local time LT), and the corresponding coefficients displaying the TEC variations in different time scales, i.e., the solar cycle, the yearly (annual and semiannual) and the diurnal universal time variations. It is found that the EOF analysis can separate the TEC variations into chief processes and the first two modes illustrate the most of the ionospheric climate properties. The first mode contains both the semiannual component which shows the semiannual ionospheric anomaly and the annual component which shows the annual or non-seasonal ionospheric anomaly. The second mode contains mainly the annual component and shows the normal seasonal ionospheric variation at most latitudes and local time sectors. The annual component in the second mode also manifests seasonal anomaly of the ionosphere at higher mid-latitudes around noontime. It is concluded that the EOF analysis, as a statistical eigen mode method, is resultful in analyzing the ionospheric climatology hence can be used to construct the empirical model for the ionospheric climatology.
基金supported by the National Natural Science Foundation of China(Grant No.90104004&10471002)973 project of China(Grant No.G1999075105)+1 种基金the Natural Science Foundation of Guangdong Province(Grant No.05008289&032038)the Doctoral Foundation of Guangdong Province(Grant No.04300917).
文摘An algorithm is presented for raising an approximation order of any given orthogonal multiscaling function with the dilation factor a. Let φ(x) = [φ1(x),φ2(x),…,φr(x)]T be an orthogonal multiscaling function with the dilation factor a and the approximation order m. We can construct a new orthogonal multiscaling function φnew(x) = [ φT(x). f3r+1(x),φr+2(x),…,φr+s(x)}T with the approximation order m + L(L ∈ Z+). In other words, we raise the approximation order of multiscaling function φ(x) by increasing its multiplicity. In addition, we discuss an especial setting. That is, if given an orthogonal multiscaling function φ(x) = [φ1 (x), φ2(x), …, φr(x)]T is symmetric, then the new orthogonal multiscaling function φnew(x) not only raise the approximation order but also preserve symmetry. Finally, some examples are given.
基金supported by the National"973" Program of China (No. 2010CB328300)the National Natural Science Foundation of China (Nos.600837004 and 60777010)+3 种基金the National "863" Program of China (Nos. 2009AA01Z253 and 2009AA01A347)the Chinese Postdoctoral Science Foundation (No.20090460593)the Shanghai Postdoctoral Science Foundation (No. 10R21411600)the Open Fund of Beijing University of Posts and Telecommunications, and the Shuguang Fund
文摘A novel scheme to generate, transmit, and receive an optical orthogonal frequency division multiplexing （OFDM） continuous phase modulation （CPM） signal, which is combining minimum shift keying （MSK） coding with OFDM optical modulation, for downlink application in a 4×2.5-Gb/s wavelength division multiplexing （WDM） passive optical access network, is proposed and experimentally validated. We also realize wavelength remodulation for carrying upstream on-off keying （OOK） data to reduce the cost budget at the optical network unit. The experimental results show that the power penalties for the downlink and the uplink data after transmission over 25-km SMF-28 fiber are 0.1 dB and smaller than 0.4 dB, respectively.
基金supported by the National"973"Program of China(Nos.2010CB328300 and 2010CB328303)the National Natural Science Foundation of China(No. 60772013)+1 种基金the National"863"Program of China(No. 2009AA03Z408)the Open Fund of Key Laboratory of Optical Communication and Lightwave Technologies Beijing University of Posts and Telecommunications, Ministry of Education,China.
文摘We propose a novel and simple all-optical 160-Gb/s orthogonal frequency division multiplexing（OFDM） symbol generator which is based on discrete triangle waveform driving-LiNbO_3 modulators to realize large-range linear optical shift.The entire system needs 64 discrete modulators：at the transmitter,a 2.5-Gb/s optical duobinary（ODB） modulator for data modulation and a 2.5-Gb/s triangle waveform driving-LiNbO_3 phase modulator for phase shift to generate each subcarrier;and at the receiver,a 2.5-GHz optical band pass filter（OBPF） using Faraday anomalous dispersion optical effect to separate them.Excellent bit error rate（BER） is observed after 1060 km of transmission without any dispersion compensation.
基金supported in part by the National Natural Science Foundation of China (No.60932004)the National "863" Program of China (Nos.2009AA01Z256, 2009AA01Z253, and 2009AA01A345)the National "973" Program of China (No.2007CB310705)
文摘We study an electronic compensator （EC） as a receiver for a 100-Gb/s polarization division multiplexing coherent optical orthogonal frequency division multiplexing （PDM-CO-OFDM） system without optical dispersion compensation.EC,including electrical dispersion compensation （EDC）,least squares channel estimation and compensation （LSCEC）,and phase compensation （PC）,is used to compensate for chromatic dispersion （CD）,phase noise,polarization mode dispersion （PMD）,and channel impairments,respectively.Simulations show that EC is highly effective in compensating for those impairments and that the performance is close to the theoretical limitation of optical signal-to-noise rate （OSNR）,CD,and PMD.Its robustness against those transmission impairments and fiber nonlinearity are also systematically studied.
基金supported by the National "973"the Program of China (Nos. 2010CB328300 and 2010CB328305)the National Natural Science Foundation of China (No. 60772013)the National "863"program of China (No. 2009AA03Z408)
文摘Phase pre-emphasis is theoretically studied and introduced to reduce peak-to-average power ratio （PAPR） in optical orthogonal frequency division multiplexing （OFDM） systems. In intensity modulated （IM） systems, simulations show noticeable PAPR reductions： 4.14 dB （N = 16） and 15.48 dB （N = 512） in time lens-based OFDM, N is the number of subcarriers. An equation is developed to calculate phase values and is proved to be effective. Optical implementing methods are proposed and analyzed. In a time lens-based OFDM system, phase pre-emphasis reduces fiber nonlinearity and results in a 5.2-dB increase of launch power at the bit error rate （BER） of 10 ？6 . Simulations also show similar PAPR reduction and fiber nonlinearity mitigation in optical inverse discrete Fourier transformer （OIDFT） based OFDM systems.
