Reverse design of highly GeO2-doped silica optical fibers with broadband and flat dispersion profiles is proposed using a neural network(NN) combined with a particle swarm optimization(PSO) algorithm.Firstly,the NN mo...Reverse design of highly GeO2-doped silica optical fibers with broadband and flat dispersion profiles is proposed using a neural network(NN) combined with a particle swarm optimization(PSO) algorithm.Firstly,the NN model designed to predict optical fiber dispersion is trained with an appropriate choice of hyperparameters,achieving a root mean square error(RMSE) of 9.47×10-7on the test dataset,with a determination coefficient(R2) of 0.999.Secondly,the NN is combined with the PSO algorithm for the inverse design of dispersion-flattened optical fibers.To expand the search space and avoid particles becoming trapped in local optimal solutions,the PSO algorithm incorporates adaptive inertia weight updating and a simulated annealing algorithm.Finally,by using a suitable fitness function,the designed fibers exhibit flat group velocity dispersion(GVD) profiles at 1 400—2 400 nm,where the GVD fluctuations and minimum absolute GVD values are below 18 ps·nm-1·km-1and 7 ps·nm-1·km-1,respectively.展开更多
The switchable dual-wavelength erbium-doped fiber laser(EDFL) with a two-mode photonic crystal fiber(PCF) loop mirror and a chirped fiber Bragg grating(CFBG) at room temperature is proposed and experimentally demonstr...The switchable dual-wavelength erbium-doped fiber laser(EDFL) with a two-mode photonic crystal fiber(PCF) loop mirror and a chirped fiber Bragg grating(CFBG) at room temperature is proposed and experimentally demonstrated.The two-mode PCF loop mirror is formed by inserting a piece of two-mode PCF into a Sagnac loop mirror,with the air-holes of the PCF intentionally collapsing at the splices.By adjusting the state of the polarization controller(PC) appropriately,the laser can be switched between the stable single-and dual-wavelength operations by means of the polarization hole burning(PHB) and spectral hole burning(SHB) effects.展开更多
The generation of a flat supercontinuum of over 80nm in the 1550nm region by injecting 1.6ps 10 GHz repetition rate optical pulses into an 80-m-long dispersion-flattened microstructure fibre is demonstrated. The fibre...The generation of a flat supercontinuum of over 80nm in the 1550nm region by injecting 1.6ps 10 GHz repetition rate optical pulses into an 80-m-long dispersion-flattened microstructure fibre is demonstrated. The fibre has small normal dispersion with a variation smaller than 1.5 （ps·nm^-1·km^-1） between 1500 and 1650nm. The generated supercontinuum ranging from 1513 to 1591 nm has the flatness of ±1.5 dB and it is not so flat in the range of several nanometres around the pump wavelength 1552nm. Numerical simulation is also used to study the effect of optical loss, fibre parameters and pumping conditions on supercontinuum generation in the dispersion-flattened microstructure fibre, and can be used for further optimization to generate flat broad spectra.展开更多
An up-tapered Mach-Zehnder interferometer(MZI) is proposed and demonstrated.By applying a modification setting of an existing program of the fusion splicer,two up-tapers are fabricated by pushing both sides of the fib...An up-tapered Mach-Zehnder interferometer(MZI) is proposed and demonstrated.By applying a modification setting of an existing program of the fusion splicer,two up-tapers are fabricated by pushing both sides of the fiber to the middle.It is found that the maximum extinction ratio reaches up to 20 dB.With the fiber length of 6.3-49 cm between the two up-tapers,the free spectral range(FSR) changes from 10.7 nm to 1.3 nm.Besides,the wavelength of maximum extinction ratio shifts to the shorter wavelength in the scope of tens of nanometers,while the elongation changes from 0% to 0.23%.展开更多
A new multiple-taps and flat microwave photonic filter,which is composed of fiber Bragg grating,M-Z modulator and erbium-doped fiber,is put forward.The flat band-pass or flat band-stop response can be realized by adju...A new multiple-taps and flat microwave photonic filter,which is composed of fiber Bragg grating,M-Z modulator and erbium-doped fiber,is put forward.The flat band-pass or flat band-stop response can be realized by adjusting the coupler's factor and the reflectivity of the fiber Bragg grating or the gain of the erbium-doped fiber.The free spectral range of the filter can be tuned by controlling the length of the erbium-doped fiber.The potential and feasibility of the proposed filtering structures have been demonstrated by simulation.展开更多
An improved multiplier-free feed-forward carrier phase estimation algorithm is proposed for dual-polarization quad-rature-phase-shift-keying (DP-QPSK) with coherent detection. The bit error rate (BER) performance, blo...An improved multiplier-free feed-forward carrier phase estimation algorithm is proposed for dual-polarization quad-rature-phase-shift-keying (DP-QPSK) with coherent detection. The bit error rate (BER) performance, block length effect and linewidth tolerance of the proposed algorithm are evaluated for a 112 Gbit/s DP-QPSK system. A linewidth symbol duration product of 2.9×10-4 is demonstrated for 1 dB optical signal-to-noise-ratio (OSNR) penalty at BER of 10-3 for the proposed algorithm. The hardware complexity of the proposed multiplier-free algorithm is demonstrated to be much lower than that of the 4th power algorithm.展开更多
All-optical analog-to-digital conversion (ADC) has been extensively researched to break through the inherently limited operating speed of electronic devices. In this paper, we use the photonic crystal fiber (PCF) for ...All-optical analog-to-digital conversion (ADC) has been extensively researched to break through the inherently limited operating speed of electronic devices. In this paper, we use the photonic crystal fiber (PCF) for time-stretch (TS) analog-to-digital (A/D) conversion system through generating low noise, linear chirp distribution and flat super-continuum (SC). Based on the radio frequency (RF) analog signal modulated to the linearly chirped super-continuum, the large-dispersion photonic crystal fiber is used for time-domain stretching.展开更多
To obtain the stable operation of erbium-doped fibre laser, the simple and ideal technology is adopted by use of the erbium doped polarization maintaining fibre （EDPMF）. The design criteria of the Panda-type EDPMF a...To obtain the stable operation of erbium-doped fibre laser, the simple and ideal technology is adopted by use of the erbium doped polarization maintaining fibre （EDPMF）. The design criteria of the Panda-type EDPMF are presented, which take into account the cutoff wavelength, mode field diameter, modal birefringence and background loss. Four groups of optimum structural paramcter combinations are determined in terms of the design criteria. Two kinds of the Panda-type EDPMFs are selected to be fabricated. The fabrication process and the parameter control of the Panda-type EDPMFs are presented in detail. Their refractive index profiles, birefringence and absorption spectra are experimentally investigated. The absorption coefficient of the EDPMF, whose core is co-doped with Bi, Ga, A1 and Ge, is about 57.9dB/m at 1.53μm. Co-doping Bi, Ga and A1 can greatly increase the erbium concentration in the silica-based fibre. The high birefringence is obtained for the Panda-type EDPMF. The group birefringence of the EDPMF, whose outer cladding diameter is 125 μm, is about 4.8 × 10%^-4.展开更多
We present a stable linear-cavity single longitudinal mode （SLM） erbium-doped silica fiber laser. It consists of four fiber Bragg gratings （FBGs） directly written in a section of photosensitive erbium-doped fiber ...We present a stable linear-cavity single longitudinal mode （SLM） erbium-doped silica fiber laser. It consists of four fiber Bragg gratings （FBGs） directly written in a section of photosensitive erbium-doped fiber （EDF） to form an asymmetric three-cavity structure. The stable SLM operation at a wavelength of 1545.112 nm with a 3-dB bandwidth of 0.012 nm and an optical signal-to-noise ratio （OSNR） of about 60 dB is verified experimentally. Under laboratory conditions, the performance of a power fluctuation of less than 0.05 dB observed from the power meter for 6 h and a wavelength variation of less than 0.01 nm obtained from the optical spectrum analyzer （OSA） for about 1.5 h are demonstrated. The gain fiber length is no longer limited to only several centimeters for SLM operation because of the excellent mode-selecting ability of the asymmetric three-cavity structure. The proposed scheme provides a simple and cost-effective approach to realizing a stable SLM fiber laser.展开更多
In this paper, magnetic fluid(MF), a new type of optical functional nanomaterial with interesting optical characteristics under the external magnetic field, is adopted to form a novel fiber-optic magnetic field sensor...In this paper, magnetic fluid(MF), a new type of optical functional nanomaterial with interesting optical characteristics under the external magnetic field, is adopted to form a novel fiber-optic magnetic field sensor. The proposed sensor is based on Mach-Zehnder interferometer (MZI) and has a multimode-singlemode-multimode(MSM) fiber structure. The MSM structure was fabricated by splicing a section of uncoated single mode fiber (SMF) between two short sections of multimode fibers(MMFs) using a fiber fusion splicer. The magnetic field sensing probe was made by inserting the fiberoptic structure in an MF-filled capillary tube. Variations in an external magnetic field is seen to cause changes in the refractive index of MF. This tunable change in the refractive index with magnetic field strengths between 0.6 mT to 21.4 mT produces a shift in the peak position of the wavelength. The shift of the valley wavelength with magnetic field intensity has a good linearity of up to 99.6%. The achieved sensitivity of the proposed magnetic field sensor is 0.123 nm/mT, which is improved by several folds compared with those of most of the other reported MF-based magnetic field sensors. Furthermore, we build the corresponding circuit-based measurement system, and the experimental results show that the voltage change indirectly reflects the change of the external magnetic field strength. Therefore, this provides the potential to fiber-based magnetic field sensing applications.展开更多
The flexible structure of photonic crystal fibre not only offers novel optical properties but also brings some difficulties in keeping the fibre structure in the fabrication process which inevitably cause the optical ...The flexible structure of photonic crystal fibre not only offers novel optical properties but also brings some difficulties in keeping the fibre structure in the fabrication process which inevitably cause the optical properties of the resulting fibre to deviate from the designed properties. Therefore, a method of evaluating the optical properties of the actual fibre is necessary for the purpose of application. Up to now, the methods employed to measure the properties of the actual photonic crystal fibre often require long fibre samples or complex expensive equipments. To our knowledge, there are few studies of modeling an actual photonic crystal fibre and evaluating its properties rapidly. In this paper, a novel method, based on the combination model of digital image processing and the finite element method, is proposed to rapidly model the optical properties of the actual photonic crystal fibre. Two kinds of photonic crystal fibres made by Crystal Fiber A/S are modeled. It is confirmed from numerical results that the proposed method is simple, rapid and accurate for evaluating the optical properties of the actual photonic crystal fibre without requiring complex equipment.展开更多
We propose an approach to generate optical triangular-shaped pulse train with tunable repetition rate using quadrupling radio frequency(RF)modulation and optical grating dispersion-induced power fading.In this work,a ...We propose an approach to generate optical triangular-shaped pulse train with tunable repetition rate using quadrupling radio frequency(RF)modulation and optical grating dispersion-induced power fading.In this work,a piece of chirped fiber Bragg grating(FBG)is employed as the dispersive media to remove the undesired 8th harmonic in optical intensity.Thus,the generated harmonics of optical intensity can be corresponding to the first two Fourier components of typical periodic triangular pulses.This work also analyzes the impacts of the extinction ratio and the bias voltage drift on the harmonic distortion suppression ratio.After that,the value of the extinction ratio and the range of the bias voltage drift can be obtained.The advantage of this proposal is that it can generate high order frequency-multiplexed optical pulses train which can be applied in all optical signal processing and other fields.展开更多
A novel single-mode single-polarization （SMSP） photonic crystal fibre has been proposed and analysed based on the polarization-dependent coupling and absorption effect via a full-vector finite element method with pe...A novel single-mode single-polarization （SMSP） photonic crystal fibre has been proposed and analysed based on the polarization-dependent coupling and absorption effect via a full-vector finite element method with perfectly matched layers. The numerical results predict that very efficient SMSP operation can be achieved with both high bandwidth and high extinction ratio at low loss penalty. Effects of the fibre structural parameters on the SMSP bandwidth and extinction ratio have been explored, which will provide useful guide for the design and fabrication of the fibre. The results obtained will be instructive for the realization of new SMSP fibres with high performance.展开更多
An ultra broadband single-polarization single-mode （SPSM） photonic crystal fibre （PCF） is proposed and analysed by using the plane-wave expansion method and the beam propagation method. Numerical results demonstra...An ultra broadband single-polarization single-mode （SPSM） photonic crystal fibre （PCF） is proposed and analysed by using the plane-wave expansion method and the beam propagation method. Numerical results demonstrate that the SPSM wavelength region nearly at 580 nm in width from 1. 461μm to 2.041μm is obtained in this PCF. The start wavelength of the SPSM region is close to the hole pitch, and the width of the SPSM region increases with the increasing hole pitch. Effects of dopant concentration on SPSM properties are investigated. The confinement loss decreases and the width of SPSM region widens slightly with the increasing dopant concentration. These results offer a new possibility of fabricating active doped SPSM PCFs with high performance that is crucial for improving the performance of linearly polarized fibre lasers.展开更多
A novel optical fiber doped with nano material InP is manufactured by the modified chemical vapor deposition (MCVD). The slow light based on stimulated Brillouin scattering (SBS) in the optical fiber is studied. The r...A novel optical fiber doped with nano material InP is manufactured by the modified chemical vapor deposition (MCVD). The slow light based on stimulated Brillouin scattering (SBS) in the optical fiber is studied. The results show that a time delay of ~738 ps is obtained when the input Stokes pulse is 900 ps(FWHM) and the SBS gain is ~15. It shows that a considerable time delay and an amplification of the input light can be achieved by this novel optical fiber.展开更多
We proposed a scheme of fiber Bragg grating （FBG） sensor interrogation system based on all fiber Mach-Zehnder Interferometer （MZI） edge filter and tunable-FBG. The equal power signals from FBG sensor and tunable F...We proposed a scheme of fiber Bragg grating （FBG） sensor interrogation system based on all fiber Mach-Zehnder Interferometer （MZI） edge filter and tunable-FBG. The equal power signals from FBG sensor and tunable FBG are coupled into port 1 and port 2 of MZI respectively. The experimental results show that the interrogation precision of the proposed system is 0.02 nm in a range of I nm. Furthermore, the precision can be improved by adjusting the two interference arms of the filter.展开更多
Using two typical types of polarization controller, this paper analyses theoretically and experimentally the fact that it is necessary to adjust at least three instead of two waveplates in order to transform any state...Using two typical types of polarization controller, this paper analyses theoretically and experimentally the fact that it is necessary to adjust at least three instead of two waveplates in order to transform any state of polarization to any other output covering the entire Poincar6 sphere. The experimental results are exactly in accordance with the theory discussed in this paper. It has corrected the conventional and inaccurate point of view that two waveplates of a polarization controller are adequate to complete the transformation of state of polarization.展开更多
The noise-like pulses(NLPs)with tunable fraction of the pedestal height in the whole intensity autocorrelation(AC)trace are numerically demonstrated in the designed erbium-doped fiber(EDF)mode-locked laser,which conta...The noise-like pulses(NLPs)with tunable fraction of the pedestal height in the whole intensity autocorrelation(AC)trace are numerically demonstrated in the designed erbium-doped fiber(EDF)mode-locked laser,which contains the saturable absorber(SA)with nonlinear polarization rotation(NPR),sinusoidal-shaped or Gaussian-shaped filter,two segments of EDFs,and two pieces of single-mode fibers(SMFs)with normal dispersion and anomalous dispersion,respectively.The pedestal ratio of the intensity AC trace can be tuned by changing the gain saturation energies of EDFs.The results show that when the net cavity dispersion is 1.06 ps^(2),the tuning range of the pedestal ratio for the NLPs can reach its maximum values,which are 0.51—0.89 and 0.58—0.88 for the sinusoidal-shaped and Gaussian-shaped filters,respectively.In addition,an appropriate choice of filter bandwidth is also conducive to obtain a wide range of the tuning pedestal ratio for the intensity AC trace.展开更多
This paper presents a finite element method of calculating strain distributions in and around the self-organized GaN/AlN hexagonal quantum dots. The model is based on the continuum elastic theory, which is capable of ...This paper presents a finite element method of calculating strain distributions in and around the self-organized GaN/AlN hexagonal quantum dots. The model is based on the continuum elastic theory, which is capable of treating a quantum dot with an arbitrary shape. A truncated hexagonal pyramid shaped quantum dot is adopted in this paper. The electronic energy levels of the GaN/AlN system are calculated by solving a three-dimension effective mass Shrodinger equation including a strain modified confinement potential and polarization effects. The calculations support the previous results published in the literature.展开更多
基金supported by the Fundamental Research Funds for the Central Universities (No.2024JBZY021)the National Natural Science Foundation of China (No.61575018)。
文摘Reverse design of highly GeO2-doped silica optical fibers with broadband and flat dispersion profiles is proposed using a neural network(NN) combined with a particle swarm optimization(PSO) algorithm.Firstly,the NN model designed to predict optical fiber dispersion is trained with an appropriate choice of hyperparameters,achieving a root mean square error(RMSE) of 9.47×10-7on the test dataset,with a determination coefficient(R2) of 0.999.Secondly,the NN is combined with the PSO algorithm for the inverse design of dispersion-flattened optical fibers.To expand the search space and avoid particles becoming trapped in local optimal solutions,the PSO algorithm incorporates adaptive inertia weight updating and a simulated annealing algorithm.Finally,by using a suitable fitness function,the designed fibers exhibit flat group velocity dispersion(GVD) profiles at 1 400—2 400 nm,where the GVD fluctuations and minimum absolute GVD values are below 18 ps·nm-1·km-1and 7 ps·nm-1·km-1,respectively.
基金supported by the National Natural Science Foundation of China (No.60777033)the Key Project of Ministry of Education of China (No.308002)the Innovation Foundation of Science and Technology for Excellent Doctorial Candidates of Beijing Jiaotong University(No.141045522)
文摘The switchable dual-wavelength erbium-doped fiber laser(EDFL) with a two-mode photonic crystal fiber(PCF) loop mirror and a chirped fiber Bragg grating(CFBG) at room temperature is proposed and experimentally demonstrated.The two-mode PCF loop mirror is formed by inserting a piece of two-mode PCF into a Sagnac loop mirror,with the air-holes of the PCF intentionally collapsing at the splices.By adjusting the state of the polarization controller(PC) appropriately,the laser can be switched between the stable single-and dual-wavelength operations by means of the polarization hole burning(PHB) and spectral hole burning(SHB) effects.
文摘The generation of a flat supercontinuum of over 80nm in the 1550nm region by injecting 1.6ps 10 GHz repetition rate optical pulses into an 80-m-long dispersion-flattened microstructure fibre is demonstrated. The fibre has small normal dispersion with a variation smaller than 1.5 （ps·nm^-1·km^-1） between 1500 and 1650nm. The generated supercontinuum ranging from 1513 to 1591 nm has the flatness of ±1.5 dB and it is not so flat in the range of several nanometres around the pump wavelength 1552nm. Numerical simulation is also used to study the effect of optical loss, fibre parameters and pumping conditions on supercontinuum generation in the dispersion-flattened microstructure fibre, and can be used for further optimization to generate flat broad spectra.
基金supported by the National Natural Science Foundation of China(Nos.61177069,61275076 and 61275092)"973"Program(No.2010CB328206)
文摘An up-tapered Mach-Zehnder interferometer(MZI) is proposed and demonstrated.By applying a modification setting of an existing program of the fusion splicer,two up-tapers are fabricated by pushing both sides of the fiber to the middle.It is found that the maximum extinction ratio reaches up to 20 dB.With the fiber length of 6.3-49 cm between the two up-tapers,the free spectral range(FSR) changes from 10.7 nm to 1.3 nm.Besides,the wavelength of maximum extinction ratio shifts to the shorter wavelength in the scope of tens of nanometers,while the elongation changes from 0% to 0.23%.
基金This project has been jointly supported by the National Natural Science Foundation of China (No.60771008,60837002)the Beijing Natural Science Foundation (No.4082024)+1 种基金the Foundation for the Returning Scholars (No.2008890)the Ph.D. Program Foundation,Ministry of Education of China (No.200800040002)
文摘A new multiple-taps and flat microwave photonic filter,which is composed of fiber Bragg grating,M-Z modulator and erbium-doped fiber,is put forward.The flat band-pass or flat band-stop response can be realized by adjusting the coupler's factor and the reflectivity of the fiber Bragg grating or the gain of the erbium-doped fiber.The free spectral range of the filter can be tuned by controlling the length of the erbium-doped fiber.The potential and feasibility of the proposed filtering structures have been demonstrated by simulation.
基金the National Natural Science Foundation of China (No.61275052)the National High-Tech Research and Development Program of China (No.2007AA01Z258)+2 种基金the Fundamental Research Funds for the Central Universities (No.2009YJS005)the Major State Basic Research Development Program of China (No.2010CB328206)the Beijing Nova Program (No.2008A026)
文摘An improved multiplier-free feed-forward carrier phase estimation algorithm is proposed for dual-polarization quad-rature-phase-shift-keying (DP-QPSK) with coherent detection. The bit error rate (BER) performance, block length effect and linewidth tolerance of the proposed algorithm are evaluated for a 112 Gbit/s DP-QPSK system. A linewidth symbol duration product of 2.9×10-4 is demonstrated for 1 dB optical signal-to-noise-ratio (OSNR) penalty at BER of 10-3 for the proposed algorithm. The hardware complexity of the proposed multiplier-free algorithm is demonstrated to be much lower than that of the 4th power algorithm.
基金supported by the Doctoral Program of Higher Education Research Fund (No.1101.01.001.672)
文摘All-optical analog-to-digital conversion (ADC) has been extensively researched to break through the inherently limited operating speed of electronic devices. In this paper, we use the photonic crystal fiber (PCF) for time-stretch (TS) analog-to-digital (A/D) conversion system through generating low noise, linear chirp distribution and flat super-continuum (SC). Based on the radio frequency (RF) analog signal modulated to the linearly chirped super-continuum, the large-dispersion photonic crystal fiber is used for time-domain stretching.
文摘To obtain the stable operation of erbium-doped fibre laser, the simple and ideal technology is adopted by use of the erbium doped polarization maintaining fibre （EDPMF）. The design criteria of the Panda-type EDPMF are presented, which take into account the cutoff wavelength, mode field diameter, modal birefringence and background loss. Four groups of optimum structural paramcter combinations are determined in terms of the design criteria. Two kinds of the Panda-type EDPMFs are selected to be fabricated. The fabrication process and the parameter control of the Panda-type EDPMFs are presented in detail. Their refractive index profiles, birefringence and absorption spectra are experimentally investigated. The absorption coefficient of the EDPMF, whose core is co-doped with Bi, Ga, A1 and Ge, is about 57.9dB/m at 1.53μm. Co-doping Bi, Ga and A1 can greatly increase the erbium concentration in the silica-based fibre. The high birefringence is obtained for the Panda-type EDPMF. The group birefringence of the EDPMF, whose outer cladding diameter is 125 μm, is about 4.8 × 10%^-4.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 61077069 and 61107094)the Innovation Foundation for Excellent Doctoral Candidates of Beijing Jiaotong University, China (Grant No. 2011YJS202)
文摘We present a stable linear-cavity single longitudinal mode （SLM） erbium-doped silica fiber laser. It consists of four fiber Bragg gratings （FBGs） directly written in a section of photosensitive erbium-doped fiber （EDF） to form an asymmetric three-cavity structure. The stable SLM operation at a wavelength of 1545.112 nm with a 3-dB bandwidth of 0.012 nm and an optical signal-to-noise ratio （OSNR） of about 60 dB is verified experimentally. Under laboratory conditions, the performance of a power fluctuation of less than 0.05 dB observed from the power meter for 6 h and a wavelength variation of less than 0.01 nm obtained from the optical spectrum analyzer （OSA） for about 1.5 h are demonstrated. The gain fiber length is no longer limited to only several centimeters for SLM operation because of the excellent mode-selecting ability of the asymmetric three-cavity structure. The proposed scheme provides a simple and cost-effective approach to realizing a stable SLM fiber laser.
基金supported by the National Natural Science Foundation of China(No.11274278)
文摘In this paper, magnetic fluid(MF), a new type of optical functional nanomaterial with interesting optical characteristics under the external magnetic field, is adopted to form a novel fiber-optic magnetic field sensor. The proposed sensor is based on Mach-Zehnder interferometer (MZI) and has a multimode-singlemode-multimode(MSM) fiber structure. The MSM structure was fabricated by splicing a section of uncoated single mode fiber (SMF) between two short sections of multimode fibers(MMFs) using a fiber fusion splicer. The magnetic field sensing probe was made by inserting the fiberoptic structure in an MF-filled capillary tube. Variations in an external magnetic field is seen to cause changes in the refractive index of MF. This tunable change in the refractive index with magnetic field strengths between 0.6 mT to 21.4 mT produces a shift in the peak position of the wavelength. The shift of the valley wavelength with magnetic field intensity has a good linearity of up to 99.6%. The achieved sensitivity of the proposed magnetic field sensor is 0.123 nm/mT, which is improved by several folds compared with those of most of the other reported MF-based magnetic field sensors. Furthermore, we build the corresponding circuit-based measurement system, and the experimental results show that the voltage change indirectly reflects the change of the external magnetic field strength. Therefore, this provides the potential to fiber-based magnetic field sensing applications.
基金Project supported by the National Basic Research Program of China(Grant No.2010CB328206)the National Natural Science Foundation of China(Grant No.60977033)the Science and Technology Innovation Foundation for Excellent Doctors of Beijing Jiaotong University,China(Grant Nos.141055522 and 141060522)
文摘The flexible structure of photonic crystal fibre not only offers novel optical properties but also brings some difficulties in keeping the fibre structure in the fabrication process which inevitably cause the optical properties of the resulting fibre to deviate from the designed properties. Therefore, a method of evaluating the optical properties of the actual fibre is necessary for the purpose of application. Up to now, the methods employed to measure the properties of the actual photonic crystal fibre often require long fibre samples or complex expensive equipments. To our knowledge, there are few studies of modeling an actual photonic crystal fibre and evaluating its properties rapidly. In this paper, a novel method, based on the combination model of digital image processing and the finite element method, is proposed to rapidly model the optical properties of the actual photonic crystal fibre. Two kinds of photonic crystal fibres made by Crystal Fiber A/S are modeled. It is confirmed from numerical results that the proposed method is simple, rapid and accurate for evaluating the optical properties of the actual photonic crystal fibre without requiring complex equipment.
基金supported by the Fundamental Research Funds of the Central Universities(No.2015YJS004)
文摘We propose an approach to generate optical triangular-shaped pulse train with tunable repetition rate using quadrupling radio frequency(RF)modulation and optical grating dispersion-induced power fading.In this work,a piece of chirped fiber Bragg grating(FBG)is employed as the dispersive media to remove the undesired 8th harmonic in optical intensity.Thus,the generated harmonics of optical intensity can be corresponding to the first two Fourier components of typical periodic triangular pulses.This work also analyzes the impacts of the extinction ratio and the bias voltage drift on the harmonic distortion suppression ratio.After that,the value of the extinction ratio and the range of the bias voltage drift can be obtained.The advantage of this proposal is that it can generate high order frequency-multiplexed optical pulses train which can be applied in all optical signal processing and other fields.
基金Project supported by the National Natural Science Foundation of China （Grant Nos 60372100 and 60507007）, and the State Key Development Program for Basic Research of China （Grant No 2003CB314906）.Acknowledgment The first author Liu Xiao-Yi would like to thank professor Yu Chong-Xiu for her constant encouragement and kind support.
文摘A novel single-mode single-polarization （SMSP） photonic crystal fibre has been proposed and analysed based on the polarization-dependent coupling and absorption effect via a full-vector finite element method with perfectly matched layers. The numerical results predict that very efficient SMSP operation can be achieved with both high bandwidth and high extinction ratio at low loss penalty. Effects of the fibre structural parameters on the SMSP bandwidth and extinction ratio have been explored, which will provide useful guide for the design and fabrication of the fibre. The results obtained will be instructive for the realization of new SMSP fibres with high performance.
文摘An ultra broadband single-polarization single-mode （SPSM） photonic crystal fibre （PCF） is proposed and analysed by using the plane-wave expansion method and the beam propagation method. Numerical results demonstrate that the SPSM wavelength region nearly at 580 nm in width from 1. 461μm to 2.041μm is obtained in this PCF. The start wavelength of the SPSM region is close to the hole pitch, and the width of the SPSM region increases with the increasing hole pitch. Effects of dopant concentration on SPSM properties are investigated. The confinement loss decreases and the width of SPSM region widens slightly with the increasing dopant concentration. These results offer a new possibility of fabricating active doped SPSM PCFs with high performance that is crucial for improving the performance of linearly polarized fibre lasers.
基金supported by the National Natural Science Foun-dation of China (No.60871082 and 60544002).
文摘A novel optical fiber doped with nano material InP is manufactured by the modified chemical vapor deposition (MCVD). The slow light based on stimulated Brillouin scattering (SBS) in the optical fiber is studied. The results show that a time delay of ~738 ps is obtained when the input Stokes pulse is 900 ps(FWHM) and the SBS gain is ~15. It shows that a considerable time delay and an amplification of the input light can be achieved by this novel optical fiber.
基金This study is supported by National Natural Science Foundation ofChina (No.60507007)National Basic Research Program of China(No. 2003CB314900)Program for New Century ExcellentTalents in University (NCET, Min Zhang 2007).
文摘We proposed a scheme of fiber Bragg grating （FBG） sensor interrogation system based on all fiber Mach-Zehnder Interferometer （MZI） edge filter and tunable-FBG. The equal power signals from FBG sensor and tunable FBG are coupled into port 1 and port 2 of MZI respectively. The experimental results show that the interrogation precision of the proposed system is 0.02 nm in a range of I nm. Furthermore, the precision can be improved by adjusting the two interference arms of the filter.
基金supported by the National Natural Science Foundation of China (Grant No 60577046)the Corporative Building Project of Beijing Educational Committee of China (Grant No XK100130737) Shandong High Technology Project of China (Grant No 2006GG2201002)
文摘Using two typical types of polarization controller, this paper analyses theoretically and experimentally the fact that it is necessary to adjust at least three instead of two waveplates in order to transform any state of polarization to any other output covering the entire Poincar6 sphere. The experimental results are exactly in accordance with the theory discussed in this paper. It has corrected the conventional and inaccurate point of view that two waveplates of a polarization controller are adequate to complete the transformation of state of polarization.
基金supported by the National Natural Science Foundation of China(No.61575018)。
文摘The noise-like pulses(NLPs)with tunable fraction of the pedestal height in the whole intensity autocorrelation(AC)trace are numerically demonstrated in the designed erbium-doped fiber(EDF)mode-locked laser,which contains the saturable absorber(SA)with nonlinear polarization rotation(NPR),sinusoidal-shaped or Gaussian-shaped filter,two segments of EDFs,and two pieces of single-mode fibers(SMFs)with normal dispersion and anomalous dispersion,respectively.The pedestal ratio of the intensity AC trace can be tuned by changing the gain saturation energies of EDFs.The results show that when the net cavity dispersion is 1.06 ps^(2),the tuning range of the pedestal ratio for the NLPs can reach its maximum values,which are 0.51—0.89 and 0.58—0.88 for the sinusoidal-shaped and Gaussian-shaped filters,respectively.In addition,an appropriate choice of filter bandwidth is also conducive to obtain a wide range of the tuning pedestal ratio for the intensity AC trace.
基金supported by the State Key Development Program for Basic Research of China (Grant No 2003CB314901)the National Natural Science Foundation of China (Grant No 60644004)High School Innovation and Introducing Intellect Project of China (Grant No B07005)
文摘This paper presents a finite element method of calculating strain distributions in and around the self-organized GaN/AlN hexagonal quantum dots. The model is based on the continuum elastic theory, which is capable of treating a quantum dot with an arbitrary shape. A truncated hexagonal pyramid shaped quantum dot is adopted in this paper. The electronic energy levels of the GaN/AlN system are calculated by solving a three-dimension effective mass Shrodinger equation including a strain modified confinement potential and polarization effects. The calculations support the previous results published in the literature.
