We propose a silica-core dispersion-decreasing Bragg fiber （DDBF） of mode effective area as large as 55 μm^2 for supercontinuum （SO） generation at the pump wavelength of 1060 nm. Using a fast and simple matrix me...We propose a silica-core dispersion-decreasing Bragg fiber （DDBF） of mode effective area as large as 55 μm^2 for supercontinuum （SO） generation at the pump wavelength of 1060 nm. Using a fast and simple matrix method to model propagation in the DDBF,we have presented a general criterion to obtain the shortest length of the DDBF that would result in a broad SO spectrum. The proposed DDBF design should be amenable for reproducible fabrication through the well-developed MCVD fiber manufacturing technology and the concept has potential for realization as a practical device.展开更多
The Bose-Hubbard model describing interacting bosons in an optical lattice is reduced to a simple spin-1 XY model with single-ion anisotropy in the vicinity of the Mort phase. We propose a mean-field theory based on a...The Bose-Hubbard model describing interacting bosons in an optical lattice is reduced to a simple spin-1 XY model with single-ion anisotropy in the vicinity of the Mort phase. We propose a mean-field theory based on a constraint SU（3） pseudo-boson representation on the effective model to study the properties of the superfluid-Mott-insulator phase transition. By calculating the elementary excitation spectra and the average particle number tluctuation in the Brillouin zone center, we lind that the energy gaps vanish continuously around （JXY/Jz）c≈ 0.175 and （JxY/Jz）c ≈ 0.094 for 2D and 3D cubic lattices respectively, where the superfluid order parameters come up from zero and the Mort insulator state changes into a superfluid state.展开更多
The Green＇s function and the higher-order correlation functions of spin-1 cold atoms in an optical lattice are defined. Because we consider the problem of spin-1 Bose condensed atoms in an optical lattice with high f...The Green＇s function and the higher-order correlation functions of spin-1 cold atoms in an optical lattice are defined. Because we consider the problem of spin-1 Bose condensed atoms in an optical lattice with high filling factors, i.e., the number density of Bose condensed atoms no is large, the fluctuation of them can be neglected and we take mean-field approximation for the higher-order terms. The excitation spectra for both the polar case and the ferromagnetic case are obtained and analyzed.展开更多
A new method based on the traditional method of ray scanning has been introduced to resolve the problem of judging the color in the chromaticity diagram by employing the line segments approximate curve—— using polyg...A new method based on the traditional method of ray scanning has been introduced to resolve the problem of judging the color in the chromaticity diagram by employing the line segments approximate curve—— using polygonal approximate closed curve. Then a vector coordinate could be used to describe the curve instead of curve equations. So it is easy to judge the topology relation between an area and a point or a locus. And any data processing method has been used to save memory, which makes the improved ray scanning method is quite useful in the measurement of color.展开更多
By introducing a two-stage polarization mode dispersion (PMD) compensator after a optical fiber link with a large PMD,over 270 ps first-order and 2 000 ps^2 high-order PMD was compensated.The results show that the two...By introducing a two-stage polarization mode dispersion (PMD) compensator after a optical fiber link with a large PMD,over 270 ps first-order and 2 000 ps^2 high-order PMD was compensated.The results show that the two-stage compensator can be used to PMD compensation in the 20 Gb/s optical time division multiplexing system with 60 km high PMD fiber.After compensating,the 270 ps DGD is changed into max.7 ps.Moreover,the tunable FBG has a function of dispersion compensation.展开更多
A 10 Gbit/s recirculating system is configured with Chirped Fiber Bragg Grating (CFBG) for the dispersion compensation. For the first time, the transmission distance in the loop reaches 1000km with bit error rate of 1...A 10 Gbit/s recirculating system is configured with Chirped Fiber Bragg Grating (CFBG) for the dispersion compensation. For the first time, the transmission distance in the loop reaches 1000km with bit error rate of 10-9. The effect of the group delay ripple of the fiber grating is also investigated in the recirculating systems, and it is shown that the transmission distance is limited to 4 cycles (4× 167.1km ) in the loop with the power penalty fluctuation below 1.0dB. Thus the group delay ripple should be reduced to allow for the wavelength drift of ±5GHz.At the end of this letter, the principles are given for designing long haul recirculating systems with dispersion compensation CFBG.展开更多
The achievement in optical/digital color photography based on white-light information processing including the color-encoding camera, the color image decoder, the integral window Fourier algorithm of the Fourier trans...The achievement in optical/digital color photography based on white-light information processing including the color-encoding camera, the color image decoder, the integral window Fourier algorithm of the Fourier transform in digital decoding, the color correction of the retrieval color image and the fusion of zero order diffraction is reported. This technique has found its important applications in the fields of aerial reconnaissance photography and far-distance ground photography due to its features of large information capacity, convenience in archival storage, the capability of color enhancement, particularly easy transportation by Internet.展开更多
In the three-dimensional(3D) contour measurement,the phase shift profilometry(PSP) method is the most widely used one.However,the measurement speed of PSP is very low because of the multiple projections.In order to im...In the three-dimensional(3D) contour measurement,the phase shift profilometry(PSP) method is the most widely used one.However,the measurement speed of PSP is very low because of the multiple projections.In order to improve the measurement speed,color grating stripes are used for measurement in this paper.During the measurement,only one color sinusoidal fringe is projected on the measured object.Therefore,the measurement speed is greatly improved.Since there is coupling or interference phenomenon between the adjacent color grating stripes,a color correction method is used to improve the measurement results.A method for correcting nonlinear error of measurement system is proposed in this paper,and the sinusoidal property of acquired image after correction is better than that before correction.Experimental results show that with these correction methods,the measurement errors can be reduced.Therefore,it can support a good foundation for the high-precision 3D reconstruction.展开更多
We propose an arrayed waveguide grating(AWG)-based 10 Gbit/s per channel full duplex wavelength division multiplexing passive optical network(WDM-PON).A chirp managed directly modulated laser with return-to-zero(RZ) d...We propose an arrayed waveguide grating(AWG)-based 10 Gbit/s per channel full duplex wavelength division multiplexing passive optical network(WDM-PON).A chirp managed directly modulated laser with return-to-zero(RZ) differential phase shift keying(DPSK) modulation technique is utilized for downlink(DL) direction,and then the downlink signal is re-modulated for the uplink(UL) direction using intensity modulation technique with the data rate of 10 Gbit/s per channel.A successful WDM-PON transmission operation with the data rate of 10 Gbit/s per channel over a distance of 25 km without any optical amplification or dispersion compensation is demonstrated with low power penalty.展开更多
We analyze the effects of average index variation on the transmission characteristics of an index-apodized long-period fiber grating （LPFG） by the transfer matrix method and study how these effects depend on the gra...We analyze the effects of average index variation on the transmission characteristics of an index-apodized long-period fiber grating （LPFG） by the transfer matrix method and study how these effects depend on the grating length, the grating profile, the modal dispersion factor, and the duty cycle of the index modulation. Apart from shifting the resonance wavelength and modifying the rejection band, average index variation can give rise to significant side lobes that may appear on the short-wavelength or long-wavelength side of the rejection band, depending on the signs of the average index change and the modal dispersion factor. Our results provide general guidance for the writing of LPFGs for the minimization of side lobes. Our analysis compares well with published experimental results and should be useful for the design and fabrication of LPFGs.展开更多
文摘We propose a silica-core dispersion-decreasing Bragg fiber （DDBF） of mode effective area as large as 55 μm^2 for supercontinuum （SO） generation at the pump wavelength of 1060 nm. Using a fast and simple matrix method to model propagation in the DDBF,we have presented a general criterion to obtain the shortest length of the DDBF that would result in a broad SO spectrum. The proposed DDBF design should be amenable for reproducible fabrication through the well-developed MCVD fiber manufacturing technology and the concept has potential for realization as a practical device.
文摘The Bose-Hubbard model describing interacting bosons in an optical lattice is reduced to a simple spin-1 XY model with single-ion anisotropy in the vicinity of the Mort phase. We propose a mean-field theory based on a constraint SU（3） pseudo-boson representation on the effective model to study the properties of the superfluid-Mott-insulator phase transition. By calculating the elementary excitation spectra and the average particle number tluctuation in the Brillouin zone center, we lind that the energy gaps vanish continuously around （JXY/Jz）c≈ 0.175 and （JxY/Jz）c ≈ 0.094 for 2D and 3D cubic lattices respectively, where the superfluid order parameters come up from zero and the Mort insulator state changes into a superfluid state.
基金The project supported by National Natural Science Foundation of China under Grant Nos. 10547107 and 10571091
文摘The Green＇s function and the higher-order correlation functions of spin-1 cold atoms in an optical lattice are defined. Because we consider the problem of spin-1 Bose condensed atoms in an optical lattice with high filling factors, i.e., the number density of Bose condensed atoms no is large, the fluctuation of them can be neglected and we take mean-field approximation for the higher-order terms. The excitation spectra for both the polar case and the ferromagnetic case are obtained and analyzed.
基金Key Projects from Science & Technology Depart ment of Hubei Province(2002AA101B06)
文摘A new method based on the traditional method of ray scanning has been introduced to resolve the problem of judging the color in the chromaticity diagram by employing the line segments approximate curve—— using polygonal approximate closed curve. Then a vector coordinate could be used to describe the curve instead of curve equations. So it is easy to judge the topology relation between an area and a point or a locus. And any data processing method has been used to save memory, which makes the improved ray scanning method is quite useful in the measurement of color.
文摘By introducing a two-stage polarization mode dispersion (PMD) compensator after a optical fiber link with a large PMD,over 270 ps first-order and 2 000 ps^2 high-order PMD was compensated.The results show that the two-stage compensator can be used to PMD compensation in the 20 Gb/s optical time division multiplexing system with 60 km high PMD fiber.After compensating,the 270 ps DGD is changed into max.7 ps.Moreover,the tunable FBG has a function of dispersion compensation.
基金the National 863 High Technology Development Program of China (No.2001 AA122012)
文摘A 10 Gbit/s recirculating system is configured with Chirped Fiber Bragg Grating (CFBG) for the dispersion compensation. For the first time, the transmission distance in the loop reaches 1000km with bit error rate of 10-9. The effect of the group delay ripple of the fiber grating is also investigated in the recirculating systems, and it is shown that the transmission distance is limited to 4 cycles (4× 167.1km ) in the loop with the power penalty fluctuation below 1.0dB. Thus the group delay ripple should be reduced to allow for the wavelength drift of ±5GHz.At the end of this letter, the principles are given for designing long haul recirculating systems with dispersion compensation CFBG.
文摘The achievement in optical/digital color photography based on white-light information processing including the color-encoding camera, the color image decoder, the integral window Fourier algorithm of the Fourier transform in digital decoding, the color correction of the retrieval color image and the fusion of zero order diffraction is reported. This technique has found its important applications in the fields of aerial reconnaissance photography and far-distance ground photography due to its features of large information capacity, convenience in archival storage, the capability of color enhancement, particularly easy transportation by Internet.
基金supported by the National Natural Science Foundation of China(Nos.60808020 and 61078041)the National Science and Technology Support(No.2014BAH03F01)+1 种基金the Tianjin Research Program of Application Foundation and Advanced Technology(No.10JCYBJC07200)the Technology Program of Tianjin Municipal Education Commission(No.20130324)
文摘In the three-dimensional(3D) contour measurement,the phase shift profilometry(PSP) method is the most widely used one.However,the measurement speed of PSP is very low because of the multiple projections.In order to improve the measurement speed,color grating stripes are used for measurement in this paper.During the measurement,only one color sinusoidal fringe is projected on the measured object.Therefore,the measurement speed is greatly improved.Since there is coupling or interference phenomenon between the adjacent color grating stripes,a color correction method is used to improve the measurement results.A method for correcting nonlinear error of measurement system is proposed in this paper,and the sinusoidal property of acquired image after correction is better than that before correction.Experimental results show that with these correction methods,the measurement errors can be reduced.Therefore,it can support a good foundation for the high-precision 3D reconstruction.
基金supported by the National Basic Research Program of China (No.2010CB328300)the Fundamental Research Funds for the Central Universities (No.2009RC0314)+3 种基金the National Natural Science Foundation of China (Nos.61077050,61077014 and 60932004)the BUPT Young Foundation (No.2009CZ07)the Fundamental Research Funds for the Central Universitiesthe Open Foundation of State Key Laboratory of Optical Communication Technologies and Networks (WRI)(No.2010OCTN-02)
文摘We propose an arrayed waveguide grating(AWG)-based 10 Gbit/s per channel full duplex wavelength division multiplexing passive optical network(WDM-PON).A chirp managed directly modulated laser with return-to-zero(RZ) differential phase shift keying(DPSK) modulation technique is utilized for downlink(DL) direction,and then the downlink signal is re-modulated for the uplink(UL) direction using intensity modulation technique with the data rate of 10 Gbit/s per channel.A successful WDM-PON transmission operation with the data rate of 10 Gbit/s per channel over a distance of 25 km without any optical amplification or dispersion compensation is demonstrated with low power penalty.
文摘We analyze the effects of average index variation on the transmission characteristics of an index-apodized long-period fiber grating （LPFG） by the transfer matrix method and study how these effects depend on the grating length, the grating profile, the modal dispersion factor, and the duty cycle of the index modulation. Apart from shifting the resonance wavelength and modifying the rejection band, average index variation can give rise to significant side lobes that may appear on the short-wavelength or long-wavelength side of the rejection band, depending on the signs of the average index change and the modal dispersion factor. Our results provide general guidance for the writing of LPFGs for the minimization of side lobes. Our analysis compares well with published experimental results and should be useful for the design and fabrication of LPFGs.
