A tunable negative coefficient band-pass microwave photonic filter (MPF) with improved mainlobe-to-sidelobe sup-pression ratio (MSSR) by a Sagnac interferometer (SI) is experimentally demonstrated. The negative coeffi...A tunable negative coefficient band-pass microwave photonic filter (MPF) with improved mainlobe-to-sidelobe sup-pression ratio (MSSR) by a Sagnac interferometer (SI) is experimentally demonstrated. The negative coefficient characteristic of MPF is achieved by using the phase modulation technology. The central frequency of the band-pass MPF is tunable continuously by changing the wavelength separation of multi-wavelength optical carriers. A 38-tap negative coefficient band-pass MPF whose MSSR is increased by about 6.371 dB is achieved in experiment by apodizing the tap coefficient with the Sagnac interferometer.展开更多
A tunable microwave photonic bandpass filter with high mainlobe-to-sidelobe ratio (MSR) based on a phase modulator and a dispersive device is proposed. The multi-tap characteristics of the filter are realized by slici...A tunable microwave photonic bandpass filter with high mainlobe-to-sidelobe ratio (MSR) based on a phase modulator and a dispersive device is proposed. The multi-tap characteristics of the filter are realized by slicing a broadband source using a Mach-Zehnder interferometer (MZI) which results in a high MSR of 25 dB. The tunability of the filter is realized by an optical variable delay line (OVDL) in one arm of the MZI, which changes the wavelength spacing of the sliced broadband source and results in a tunable free spectrum range (FSR) of the filter. The central frequency of the bandpass filter is tunable from 10.7 GHz to 27 GHz by changing the wavelength spacing from 0.145 nm to 0.054 nm.展开更多
Multi-π-phase-shifted fiber Bragg gratings and π-phase-shifted sampled fiber Bragg gratings(SFBGs) with dual wavelength filtering properties are compared.Results show that both of these gratings have the dual wavele...Multi-π-phase-shifted fiber Bragg gratings and π-phase-shifted sampled fiber Bragg gratings(SFBGs) with dual wavelength filtering properties are compared.Results show that both of these gratings have the dual wavelength reflective spectra.However,the side lobe of the reflective spectrum of π-phase-shifted SFBGs is lower than that of multi-π-phaseshifted gratings.By adjusting the duty cycle in the range of 0.66-0.80,the filtering properties of π-phase-shifted SFBGs are optimized,and the side lobe suppression ratio(SLSR) is the lowest when the duty cycle is 0.75.The application of the π-phase-shifted SFBGs in the dual-wavelength laser is also demonstrated.展开更多
In this paper,we propose a method to realize microwave photonic filter(MPF) with complex coefficient,whose central frequency f 0 and 3 dB bandwidth are tunable.The complex coefficient is realized by multi-wavelength o...In this paper,we propose a method to realize microwave photonic filter(MPF) with complex coefficient,whose central frequency f 0 and 3 dB bandwidth are tunable.The complex coefficient is realized by multi-wavelength optical source and stimulated Brillouin scattering(SBS).The central frequency of the filter is tuned by adjusting the phase shift caused by SBS without changing its frequency response.The frequency selectivity of filter can be improved through increasing the bandwidth of broadband optical source(BOS) or decreasing wavelength separation to increase the taps of MPF.The mainlobeto-sidelobe suppression ratio(MSSR) of the filter is affected by the weight of each tap.When the length of fiber is 0.5544 m in birefringence fiber loop mirror(FLM),the MSSR is improved by 18.55 dB compared with that without the weight controlling.展开更多
An all fiber magnetic field sensor with peanut-shape structure based on multimode fiber(MMF) is proposed and experimentally demonstrated. The sensing structure and magnetic fluid(MF) are both encapsulated in capillary...An all fiber magnetic field sensor with peanut-shape structure based on multimode fiber(MMF) is proposed and experimentally demonstrated. The sensing structure and magnetic fluid(MF) are both encapsulated in capillary, and the effective refractive index of MF is affected by surrounding magnetic field strength. The measurement of magnetic field is realized by observing the wavelength drift of interference peak. The transmission spectrum generated by Mach-Zehnder interferometer(MZI) includes core-core mode interference and core-cladding mode interference. Experimental results demonstrate that the core-cladding mode interference is sensitive to magnetic field, and the magnetic field sensitivity is 0.047 8 nm/mT. In addition, two kinds of interference dips are sensitive to temperature, and the sensitivities are 0.060 0 nm/°C and 0.052 6 nm/°C, respectively. So the simultaneous measurement of magnetic field strength and temperature can be achieved based on sensitivity matrix.展开更多
A microwave photonic filter(MPF) based on multi-wavelength fiber laser and infinite impulse response(IIR) is proposed. The filter uses a multi-wavelength fiber laser as the light source, two sections of polarization m...A microwave photonic filter(MPF) based on multi-wavelength fiber laser and infinite impulse response(IIR) is proposed. The filter uses a multi-wavelength fiber laser as the light source, two sections of polarization maintaining fiber(PMF) and three polarization controllers(PCs) as the laser frequency selection device. By adjusting the PC to change the effective length of the PMF, the laser can obtain three wavelength spacings, which are 0.44 nm, 0.78 nm and 1.08 nm, respectively. And the corresponding free spectral ranges(FSRs) are 8.46 GHz, 4.66 GHz and 3.44 GHz, respectively. Thus changing the wavelength spacing of the laser can make the FSR variable. An IIR filter is introduced based on a finite impulse response(FIR) filter. Then the 3-d B bandwidth of the MPF is reduced, and the main side-lobe suppression ratio(MSSR) is increased. By adjusting the gain of the radio frequency(RF) signal amplifier, the frequency response of the filter can be enhanced.展开更多
A widely tunable microwave photonic notch filter with adjustable bandwidth based on multi-wavelength fiber laser is proposed and demonstrated.The multi-wavelength fiber laser generates the multi-taps of the microwave ...A widely tunable microwave photonic notch filter with adjustable bandwidth based on multi-wavelength fiber laser is proposed and demonstrated.The multi-wavelength fiber laser generates the multi-taps of the microwave photonic filter(MPF).In order to obtain notch frequency response,a Fourier-domain optical processor(FD-OP)is introduced to con-trol the amplitude and phase of the optical carrier and phase modulation sidebands.By adjusting the polarization con-troller(PC),different numbers of taps are got,such as 6,8,10 and 121 And the wavelength-spacing of the multi-wavelength laser is 0.4 nm.The bandwidth of the notch filter is changed by adjusting the number of taps and the corresponding bandwidths are 4.41 GHz,3.30 GHz,2.64 GHz and 2.19 GHz,respectively.With the additional phase shift introduced by FD-OP,the notch position is continuously ttmed in the whole free spectral range(FSR)of 27.94 GHz.The center frequency of the notch filter can be continuously tuned from 13.97 GHz to 41.91 GHz.展开更多
We present an all-digital demodulation system of interferometric fiber optic sensor based on an improved arctangent-differential-self-multiplying(arctan-DSM)algorithm.The total harmonic distortion(THD)and the light in...We present an all-digital demodulation system of interferometric fiber optic sensor based on an improved arctangent-differential-self-multiplying(arctan-DSM)algorithm.The total harmonic distortion(THD)and the light intensity disturbance(LID)are also suppressed,the same as those in the traditional arctan-DSM algorithm.Moreover,the lowest sampling frequency is also reduced by introducing anti-aliasing filter,so the occupation of the system memory is reduced.The simulations show that the improved algorithm can correctly demodulate cosine signal and chirp signal with lower sampling frequency.展开更多
In this paper, a dynamic optical arbitrary waveform generator(OAWG) based on cross phase modulation(XPM) is proposed. According to the characteristics of XPM, the nonlinear phase shift of signal can be changed along w...In this paper, a dynamic optical arbitrary waveform generator(OAWG) based on cross phase modulation(XPM) is proposed. According to the characteristics of XPM, the nonlinear phase shift of signal can be changed along with the pump power. The amplitude of signal can be changed by controlling the phase shift at one arm of a Mach-Zehnder interferometer(MZI) using XPM effect between signal and pump. Therefore, the phase and amplitude of the optical frequency comb(OFC) can be controlled by two pump arrays. As a result, different kinds of waveforms can be synthesized. Due to the ultrafast response of XPM, the generated waveform could be dynamically updated with an ultrafast frequency. The waveform fidelity is affected by the updating frequency.展开更多
An optical fiber magnetic field sensor for the dual-parameter simultaneous measurement is proposed and demonstrated. The sensor head is constructed by a peanut-shape structure and long period fiber grating(LPFG) coate...An optical fiber magnetic field sensor for the dual-parameter simultaneous measurement is proposed and demonstrated. The sensor head is constructed by a peanut-shape structure and long period fiber grating(LPFG) coated by magnetic fluid(MF). The external magnetic field intensity can be measured by the variation of characteristic wavelength(Dip1 and Dip2) in interference spectrum since the effective refractive index of MF changes with external magnetic field intensity. When the external magnetic field intensity changes from 0 mT to 20 mT, the magnetic field sensitivities of Dip1 and Dip2 are -0.064 nm/mT and -0.041 nm/mT, respectively. Experimental results show that the temperature sensitivities of the Dip1 and Dip2 are 0.233 nm/℃ and 0.186 nm/°C, respectively. Therefore, the simultaneous measurement of the magnetic field intensity and temperature is demonstrated based on the sensitive matrix. It has some potential applications in aerospace, environmental monitoring and medical sensing fields.展开更多
A nonlinear optical loop mirror (NOLM) constructed with linear dispersion decreasing fiber (DDF) is used to compress a beat signal. Several factors impacting on quality of output pulse in this compression system, such...A nonlinear optical loop mirror (NOLM) constructed with linear dispersion decreasing fiber (DDF) is used to compress a beat signal. Several factors impacting on quality of output pulse in this compression system, such as dispersion slope of DDF, power-splitting ratio, incident pulse shape and peak power, are analyzed numerically. The new method for selecting device characteristics is adopted to enable both good pedestal suppression and pulse compression. As a result, the output pulse train with tunable and high repetition rate, pedestal energy of 5.09%, compression ratio of 25.6 and energy transmissivity of 50.56% is obtained by using 0.524 km-long DDF with dispersion slope of 26 ps^2/km^2 and a coupler with power-splitting ratio of 0.54.展开更多
A microwave photonic notch filter with a complex coefficient is proposed and demonstrated based on four wave mixing(FWM). FWM effect of two single-frequency laser beams occurs in a highly nonlinear fiber(HNLF), and mu...A microwave photonic notch filter with a complex coefficient is proposed and demonstrated based on four wave mixing(FWM). FWM effect of two single-frequency laser beams occurs in a highly nonlinear fiber(HNLF), and multi-wavelength optical signals are generated and used to generate the multi-tap of microwave photonic filter(MPF). The complex coefficient is generated by using a Fourier-domain optical processor(FD-OP) to control the amplitude and phase of the optical carrier and phase modulation sidebands. The results show that this filter can be changed from bandpass filter to notch filter by controlling the FD-OP. The center frequency of the notch filter can be continuously tuned from 5.853 GHz to 29.311 GHz with free spectral range(FSR) of 11.729 GHz. The shape of the frequency response keeps unchanged when the phase is tuned.展开更多
A continuously tunable microwave photonic notch filter with complex coefficient based on phase modulation is proposed and demonstrated. The complex coefficient is generated using a Fourier-domain optical processor(FD-...A continuously tunable microwave photonic notch filter with complex coefficient based on phase modulation is proposed and demonstrated. The complex coefficient is generated using a Fourier-domain optical processor(FD-OP) to control the amplitude and phase of the optical carrier and radio-frequency(RF) phase modulation sidebands. By controlling the FD-OP,the frequency response of the filter can be tuned in the full free spectral range(FSR) without changing the shape and the FSR of the frequency response. The results show that the center frequency of the notch filter can be continuously tuned from 17.582 GHz to 29.311 GHz with FSR of 11.729 GHz. The shape of the frequency response keeps unchanged when the phase is tuned.展开更多
In order to solve the problem of poor tuning performence of the optical arbitrary waveform generator based on fiber Bragg grating and piezoelectric transducer,a novel multi-parameter fast tunable Bragg grating filter ...In order to solve the problem of poor tuning performence of the optical arbitrary waveform generator based on fiber Bragg grating and piezoelectric transducer,a novel multi-parameter fast tunable Bragg grating filter on lithium niobate crystal was proposed.Theory analysis shows that its Bragg wavelength and corresponding phase is tunable in a linear way with wavelength tuning efficiency of 15.6 pm/V and phase tuning efficiency of O.2 n/V,and the output light intensity of the filter is controlled by adjusting a polarization rotator also.Simulation results based on transfer matrix theory show that the maximum filtering reflectivity is achieved with the etching duty cycle 1/2,reflectivity more than 98.4%and bandwidth wider than O.14 nm is obtained when etching depth is deeper than 100 nm on the condition of 10.87 mm grating length,and increasing the wavelength tuning voltage will further reduce the filter bandwidth.展开更多
文摘A tunable negative coefficient band-pass microwave photonic filter (MPF) with improved mainlobe-to-sidelobe sup-pression ratio (MSSR) by a Sagnac interferometer (SI) is experimentally demonstrated. The negative coefficient characteristic of MPF is achieved by using the phase modulation technology. The central frequency of the band-pass MPF is tunable continuously by changing the wavelength separation of multi-wavelength optical carriers. A 38-tap negative coefficient band-pass MPF whose MSSR is increased by about 6.371 dB is achieved in experiment by apodizing the tap coefficient with the Sagnac interferometer.
基金supported by the National Natural Science Foundation of China (No.60808004)the New Century Excellent Talents in University (No.NCET-07-0611)the Tianjin Natural Science Foundation (No.08JCYBJC14500)
文摘A tunable microwave photonic bandpass filter with high mainlobe-to-sidelobe ratio (MSR) based on a phase modulator and a dispersive device is proposed. The multi-tap characteristics of the filter are realized by slicing a broadband source using a Mach-Zehnder interferometer (MZI) which results in a high MSR of 25 dB. The tunability of the filter is realized by an optical variable delay line (OVDL) in one arm of the MZI, which changes the wavelength spacing of the sliced broadband source and results in a tunable free spectrum range (FSR) of the filter. The central frequency of the bandpass filter is tunable from 10.7 GHz to 27 GHz by changing the wavelength spacing from 0.145 nm to 0.054 nm.
基金supported by the National Natural Science Foundation of China (No.60808004)the Fund of New Century Excellent Talents in University (No.NCET-07-0611)Tianjin Natural Science Foundation (No.08JCYBJC14500)
文摘Multi-π-phase-shifted fiber Bragg gratings and π-phase-shifted sampled fiber Bragg gratings(SFBGs) with dual wavelength filtering properties are compared.Results show that both of these gratings have the dual wavelength reflective spectra.However,the side lobe of the reflective spectrum of π-phase-shifted SFBGs is lower than that of multi-π-phaseshifted gratings.By adjusting the duty cycle in the range of 0.66-0.80,the filtering properties of π-phase-shifted SFBGs are optimized,and the side lobe suppression ratio(SLSR) is the lowest when the duty cycle is 0.75.The application of the π-phase-shifted SFBGs in the dual-wavelength laser is also demonstrated.
基金supported by the National Natural Science Foundation of China (No.60808004)
文摘In this paper,we propose a method to realize microwave photonic filter(MPF) with complex coefficient,whose central frequency f 0 and 3 dB bandwidth are tunable.The complex coefficient is realized by multi-wavelength optical source and stimulated Brillouin scattering(SBS).The central frequency of the filter is tuned by adjusting the phase shift caused by SBS without changing its frequency response.The frequency selectivity of filter can be improved through increasing the bandwidth of broadband optical source(BOS) or decreasing wavelength separation to increase the taps of MPF.The mainlobeto-sidelobe suppression ratio(MSSR) of the filter is affected by the weight of each tap.When the length of fiber is 0.5544 m in birefringence fiber loop mirror(FLM),the MSSR is improved by 18.55 dB compared with that without the weight controlling.
基金supported by the National High Technology Research and Development Program of China(No.2013AA014200)the National Natural Science Foundation of China(No.11444001)the Municipal Natural Science Foundation of Tianjin(No.14JCYBJC16500)
文摘An all fiber magnetic field sensor with peanut-shape structure based on multimode fiber(MMF) is proposed and experimentally demonstrated. The sensing structure and magnetic fluid(MF) are both encapsulated in capillary, and the effective refractive index of MF is affected by surrounding magnetic field strength. The measurement of magnetic field is realized by observing the wavelength drift of interference peak. The transmission spectrum generated by Mach-Zehnder interferometer(MZI) includes core-core mode interference and core-cladding mode interference. Experimental results demonstrate that the core-cladding mode interference is sensitive to magnetic field, and the magnetic field sensitivity is 0.047 8 nm/mT. In addition, two kinds of interference dips are sensitive to temperature, and the sensitivities are 0.060 0 nm/°C and 0.052 6 nm/°C, respectively. So the simultaneous measurement of magnetic field strength and temperature can be achieved based on sensitivity matrix.
基金supported by the National High Technology Research and Development Program of China(No.2013AA014200)the National Natural Science Foundation of China(No.11444001)the Tianjin Natural Science Foundation(No.14JCYBJC16500)
文摘A microwave photonic filter(MPF) based on multi-wavelength fiber laser and infinite impulse response(IIR) is proposed. The filter uses a multi-wavelength fiber laser as the light source, two sections of polarization maintaining fiber(PMF) and three polarization controllers(PCs) as the laser frequency selection device. By adjusting the PC to change the effective length of the PMF, the laser can obtain three wavelength spacings, which are 0.44 nm, 0.78 nm and 1.08 nm, respectively. And the corresponding free spectral ranges(FSRs) are 8.46 GHz, 4.66 GHz and 3.44 GHz, respectively. Thus changing the wavelength spacing of the laser can make the FSR variable. An IIR filter is introduced based on a finite impulse response(FIR) filter. Then the 3-d B bandwidth of the MPF is reduced, and the main side-lobe suppression ratio(MSSR) is increased. By adjusting the gain of the radio frequency(RF) signal amplifier, the frequency response of the filter can be enhanced.
基金supported by the National Natural Science Foundation of China(No.11444001)the Municipal Natural Science Foundation of Tianjin in China(No.14JCYBJC16500)
文摘A widely tunable microwave photonic notch filter with adjustable bandwidth based on multi-wavelength fiber laser is proposed and demonstrated.The multi-wavelength fiber laser generates the multi-taps of the microwave photonic filter(MPF).In order to obtain notch frequency response,a Fourier-domain optical processor(FD-OP)is introduced to con-trol the amplitude and phase of the optical carrier and phase modulation sidebands.By adjusting the polarization con-troller(PC),different numbers of taps are got,such as 6,8,10 and 121 And the wavelength-spacing of the multi-wavelength laser is 0.4 nm.The bandwidth of the notch filter is changed by adjusting the number of taps and the corresponding bandwidths are 4.41 GHz,3.30 GHz,2.64 GHz and 2.19 GHz,respectively.With the additional phase shift introduced by FD-OP,the notch position is continuously ttmed in the whole free spectral range(FSR)of 27.94 GHz.The center frequency of the notch filter can be continuously tuned from 13.97 GHz to 41.91 GHz.
文摘We present an all-digital demodulation system of interferometric fiber optic sensor based on an improved arctangent-differential-self-multiplying(arctan-DSM)algorithm.The total harmonic distortion(THD)and the light intensity disturbance(LID)are also suppressed,the same as those in the traditional arctan-DSM algorithm.Moreover,the lowest sampling frequency is also reduced by introducing anti-aliasing filter,so the occupation of the system memory is reduced.The simulations show that the improved algorithm can correctly demodulate cosine signal and chirp signal with lower sampling frequency.
基金supported by the National Natural Science Foundation of China(No.61377075)Program for New Century Excellent Talents in University(No.NCET-07-0611)
文摘In this paper, a dynamic optical arbitrary waveform generator(OAWG) based on cross phase modulation(XPM) is proposed. According to the characteristics of XPM, the nonlinear phase shift of signal can be changed along with the pump power. The amplitude of signal can be changed by controlling the phase shift at one arm of a Mach-Zehnder interferometer(MZI) using XPM effect between signal and pump. Therefore, the phase and amplitude of the optical frequency comb(OFC) can be controlled by two pump arrays. As a result, different kinds of waveforms can be synthesized. Due to the ultrafast response of XPM, the generated waveform could be dynamically updated with an ultrafast frequency. The waveform fidelity is affected by the updating frequency.
基金supported by the National High Technology Research and Development Program of China(863 Program)(No.2013AA014200)the National Natural Science Foundation of China(No.11444001)the Municipal Natural Science Foundation of Tianjin(No.14JCYBJC16500)
文摘An optical fiber magnetic field sensor for the dual-parameter simultaneous measurement is proposed and demonstrated. The sensor head is constructed by a peanut-shape structure and long period fiber grating(LPFG) coated by magnetic fluid(MF). The external magnetic field intensity can be measured by the variation of characteristic wavelength(Dip1 and Dip2) in interference spectrum since the effective refractive index of MF changes with external magnetic field intensity. When the external magnetic field intensity changes from 0 mT to 20 mT, the magnetic field sensitivities of Dip1 and Dip2 are -0.064 nm/mT and -0.041 nm/mT, respectively. Experimental results show that the temperature sensitivities of the Dip1 and Dip2 are 0.233 nm/℃ and 0.186 nm/°C, respectively. Therefore, the simultaneous measurement of the magnetic field intensity and temperature is demonstrated based on the sensitive matrix. It has some potential applications in aerospace, environmental monitoring and medical sensing fields.
文摘A nonlinear optical loop mirror (NOLM) constructed with linear dispersion decreasing fiber (DDF) is used to compress a beat signal. Several factors impacting on quality of output pulse in this compression system, such as dispersion slope of DDF, power-splitting ratio, incident pulse shape and peak power, are analyzed numerically. The new method for selecting device characteristics is adopted to enable both good pedestal suppression and pulse compression. As a result, the output pulse train with tunable and high repetition rate, pedestal energy of 5.09%, compression ratio of 25.6 and energy transmissivity of 50.56% is obtained by using 0.524 km-long DDF with dispersion slope of 26 ps^2/km^2 and a coupler with power-splitting ratio of 0.54.
基金supported by the National High Technology Research and Development Program of China(863 Program)(No.2013AA014200)the National Natural Science Foundation of China(No.11444001)the Municipal Natural Science Foundation of Tianjin(No.14JCYBJC16500)
文摘A microwave photonic notch filter with a complex coefficient is proposed and demonstrated based on four wave mixing(FWM). FWM effect of two single-frequency laser beams occurs in a highly nonlinear fiber(HNLF), and multi-wavelength optical signals are generated and used to generate the multi-tap of microwave photonic filter(MPF). The complex coefficient is generated by using a Fourier-domain optical processor(FD-OP) to control the amplitude and phase of the optical carrier and phase modulation sidebands. The results show that this filter can be changed from bandpass filter to notch filter by controlling the FD-OP. The center frequency of the notch filter can be continuously tuned from 5.853 GHz to 29.311 GHz with free spectral range(FSR) of 11.729 GHz. The shape of the frequency response keeps unchanged when the phase is tuned.
基金supported by the National High Technology Research and Development Program of China(863 Program)(No.2013AA014200)the National Natural Science Foundation of China(No.11444001)the Municipal Natural Science Foundation of Tianjin in China(No.14JCYBJC16500)
文摘A continuously tunable microwave photonic notch filter with complex coefficient based on phase modulation is proposed and demonstrated. The complex coefficient is generated using a Fourier-domain optical processor(FD-OP) to control the amplitude and phase of the optical carrier and radio-frequency(RF) phase modulation sidebands. By controlling the FD-OP,the frequency response of the filter can be tuned in the full free spectral range(FSR) without changing the shape and the FSR of the frequency response. The results show that the center frequency of the notch filter can be continuously tuned from 17.582 GHz to 29.311 GHz with FSR of 11.729 GHz. The shape of the frequency response keeps unchanged when the phase is tuned.
基金The National Natural Science Foundation of China(No.61377075)
文摘In order to solve the problem of poor tuning performence of the optical arbitrary waveform generator based on fiber Bragg grating and piezoelectric transducer,a novel multi-parameter fast tunable Bragg grating filter on lithium niobate crystal was proposed.Theory analysis shows that its Bragg wavelength and corresponding phase is tunable in a linear way with wavelength tuning efficiency of 15.6 pm/V and phase tuning efficiency of O.2 n/V,and the output light intensity of the filter is controlled by adjusting a polarization rotator also.Simulation results based on transfer matrix theory show that the maximum filtering reflectivity is achieved with the etching duty cycle 1/2,reflectivity more than 98.4%and bandwidth wider than O.14 nm is obtained when etching depth is deeper than 100 nm on the condition of 10.87 mm grating length,and increasing the wavelength tuning voltage will further reduce the filter bandwidth.
