This work introduces special states for light in multimode fibers featuring strongly enhanced or reduced correlations be-tween output fields in the presence of environmental temperature fluctuations.Using experimental...This work introduces special states for light in multimode fibers featuring strongly enhanced or reduced correlations be-tween output fields in the presence of environmental temperature fluctuations.Using experimentally measured multi-tem-perature transmission matrix,a set of temperature principal modes that exhibit resilience to disturbances caused by tem-perature fluctuations can be generated.Reversing this concept also allows the construction of temperature anti-principal modes,with output profiles more susceptible to temperature influences than the unmodulated wavefront.Despite changes in the length of the multimode fiber within the temperature-fluctuating region,the proposed approach remains capable of robustly controlling the temperature response within the fiber.To illustrate the practicality of the proposed spe-cial state,a learning-empowered fiber specklegram temperature sensor based on temperature anti-principal mode sensi-tization is proposed.This sensor exhibits outstanding superiority over traditional approaches in terms of resolution and accuracy.These novel states are anticipated to have wide-ranging applications in fiber communication,sensing,imaging,and spectroscopy,and serve as a source of inspiration for the discovery of other novel states.展开更多
Optical endoscopy has become an essential diagnostic and therapeutic approach in modern biomedicine for directly observing organs and tissues deep inside the human body,enabling non-invasive,rapid diagnosis and treatm...Optical endoscopy has become an essential diagnostic and therapeutic approach in modern biomedicine for directly observing organs and tissues deep inside the human body,enabling non-invasive,rapid diagnosis and treatment.Optical fiber endoscopy is highly competitive among various endoscopic imaging techniques due to its high flexibility,compact structure,excellent resolution,and resistance to electromagnetic interference.Over the past decade,endoscopes based on a single multimode optical fiber(MMF)have attracted widespread research interest due to their potential to significantly reduce the footprint of optical fiber endoscopes and enhance imaging capabilities.In comparison with other imaging principles of MMF endoscopes,the scanning imaging method based on the wavefront shaping technique is highly developed and provides benefits including excellent imaging contrast,broad applicability to complex imaging scenarios,and good compatibility with various well-established scanning imaging modalities.In this review,various technical routes to achieve light focusing through MMF and procedures to conduct the scanning imaging of MMF endoscopes are introduced.The advancements in imaging performance enhancements,integrations of various imaging modalities with MMF scanning endoscopes,and applications are summarized.Challenges specific to this endoscopic imaging technology are analyzed,and potential remedies and avenues for future developments are discussed.展开更多
A respiratory monitoring system was proposed based on optical fiber.The sensor consists of photonic crystal fiber(PCF)spliced with multimode fiber(MMF)to fabricate Michelson interferometer.The sensor is inserted into ...A respiratory monitoring system was proposed based on optical fiber.The sensor consists of photonic crystal fiber(PCF)spliced with multimode fiber(MMF)to fabricate Michelson interferometer.The sensor is inserted into an oxygen mask tube and then put on the nose and mouth to monitor the respiratory rate(RR)for different cases.The results showed that when breathing increased,the intensity of light decreased.The intensity of light in the sleeping case of breathing was more intense than that when the intensity of working sport was measured.The working sport case was a higher transmittance than that of sleeping.The sensitivity of the sensor was also measured to be 231.9 pm/RH.展开更多
We proposed a compact and tunable multimode interferometer(MMI)based on an asymmetric wavy fiber(AMWF),which has axial offset,off-center taper waist,and micro-length.The fabrication process only contains non-axis pull...We proposed a compact and tunable multimode interferometer(MMI)based on an asymmetric wavy fiber(AMWF),which has axial offset,off-center taper waist,and micro-length.The fabrication process only contains non-axis pulling processes of single-mode fiber on two close positions.Theoretical qualitative analyses and experiments verify the tunable multimode propagation of the AMWF.Experimental results show a nonlinear wavelength response with increasing axis displacement from 0 to 120μm.In the range of 0—10μm,the sensitivity reaches the highest value of-1.33 nm/μm.Owing to its cost-effective,high-compact and tunable multimode propagation properties,the AMWF provides a promising platform for micro-nano photonic devices and optical sensing applications.展开更多
Imaging through multimode fiber(MMF)provides high-resolution imaging through a fiber with cross section down to tens of micrometers.It requires interferometry to measure the full transmission matrix(TM),leading to the...Imaging through multimode fiber(MMF)provides high-resolution imaging through a fiber with cross section down to tens of micrometers.It requires interferometry to measure the full transmission matrix(TM),leading to the drawbacks of complicated experimental setup and phase instability.Reference-less TM retrieval is a promising robust solution that avoids interferometry,since it recovers the TM from intensity-only measurements.However,the long computational time and failure of 3D focusing still limit its application in MMF imaging.We propose an efficient reference-less TM retrieval method by developing a nonlinear optimization algorithm based on fast Fourier transform(FFT).Furthermore,we develop an algorithm to correct the phase offset error of retrieved TM using defocused intensity images and hence achieve 3D focusing.The proposed method is validated by both simulations and experiments.The FFT-based TM retrieval algorithm achieves orders of magnitude of speedup in computational time and recovers 2286×8192 TM of a 0.22 NA and 50μm diameter MMF with 112.9 s by a computer of 32 CPU cores.With the advantages of efficiency and correction of phase offset,our method paves the way for the application of reference-less TM retrieval in not only MMF imaging but also broader applications requiring TM calibration.展开更多
Transmission matrix(TM)allows light control through complex media,such as multimode fibers(MMFs),gaining great attention in areas,such as biophotonics,over the past decade.Efforts have been taken to retrieve a complex...Transmission matrix(TM)allows light control through complex media,such as multimode fibers(MMFs),gaining great attention in areas,such as biophotonics,over the past decade.Efforts have been taken to retrieve a complex-valued TM directly from intensity measurements with several representative phase-retrieval algorithms,which still see limitations of slow or suboptimum recovery,especially under noisy environments.Here,we propose a modified nonconvex optimization approach.Through numerical evaluations,it shows that the optimum focusing efficiency is approached with less running time or sampling ratio.The comparative tests under different signal-to-noise levels further indicate its improved robustness.Experimentally,the superior focusing performance of our algorithm is collectively validated by single-and multispot focusing;especially with a sampling ratio of 8,it achieves a 93.6%efficiency of the gold-standard holography method.Based on the recovered TM,image transmission through an MMF is realized with high fidelity.Due to parallel operation and GPU acceleration,our nonconvex approach retrieves a 8685×1024 TM(sampling ratio is 8)with 42.3 s on average on a regular computer.The proposed method provides optimum efficiency and fast execution for TM retrieval that avoids the need for an external reference beam,which will facilitate applications of deep-tissue optical imaging,manipulation,and treatment.展开更多
A novel tunable comb filter composed of a single-mode/multimode/polarization-maintaining-fiber-based Sagnac fiber loop is proposed and experimentally demonstrated. The filter tunability is achieved by rotating the pol...A novel tunable comb filter composed of a single-mode/multimode/polarization-maintaining-fiber-based Sagnac fiber loop is proposed and experimentally demonstrated. The filter tunability is achieved by rotating the polarization controller. The spectral shift is dependent on rotation direction and the position of the polarization controller. In addition, the adjustable range achieved by rotating the half-wave-plate polarization controller is twice higher than that of the quarter-wave-plate one.展开更多
We propose the trench-assisted multimode fiber(TA-OM4)as a novel sensing fiber in forward Brillouin scattering(FBS)-based temperature sensor,due to its higher temperature sensitivity,better bending resistance and lowe...We propose the trench-assisted multimode fiber(TA-OM4)as a novel sensing fiber in forward Brillouin scattering(FBS)-based temperature sensor,due to its higher temperature sensitivity,better bending resistance and lower propagation loss,compared with the single mode fiber(SMF)and other sensing fibers.The FBS effect and acousto-optic interaction in TA-OM4 are the first time to be demonstrated and characterized at 1550 nm theoretically and experimentally.A 2.0 km long TA-OM4 is put into an oven to measure its temperature sensitivity,which can reach up to 80.3 kHz/℃,exceeding 53%of SMF(52.4 kHz/℃).The simulated and experimental results verify that the TA-OM4 may be a good candidate as the sensing fiber for the FBS-based temperature sensor.展开更多
We numerically investigate the mid-infrared(MIR)supercontinuum(SC)and SC-based optical frequency comb(OFC)generations when the three optical modes(LP_(01),LP_(02),and LP_(12))are considered in a multimode tellurite ph...We numerically investigate the mid-infrared(MIR)supercontinuum(SC)and SC-based optical frequency comb(OFC)generations when the three optical modes(LP_(01),LP_(02),and LP_(12))are considered in a multimode tellurite photonic crystal fiber(MM-TPCF).The geometrical parameters of the MM-TPCF are optimized to support the multimode propagation and obtain the desired dispersion characteristics of the considered three optical modes.When the pump pulse with center wavelengthλ=2.5μm,width T=80 fs,and peak power P=18 kW is coupled into the anomalous dispersion region of the LP_(01),LP_(02),and LP_(12)modes of the MM-TPCF,the-40-dB bandwidth of the generated MIR SCs can be up to 2.56,1.39,and 1.12 octaves,respectively,along with good coherence.Moreover,the nonlinear dynamics of the generated SCs are analyzed.Finally,the MIR SCs-based OFCs are demonstrated when a train of 50 pulses at 1-GHz repetition rate is used as the pump source and launched into the MM-TPCF.展开更多
A refractive index （RI） sensor based on hybrid long-period fiber grating （LPFG） with multimode fiber core （MMFC） is proposed and demonstrated. The surrounding RI can be determined by monitoring the separation be...A refractive index （RI） sensor based on hybrid long-period fiber grating （LPFG） with multimode fiber core （MMFC） is proposed and demonstrated. The surrounding RI can be determined by monitoring the separation between the resonant wavelengths of the LPFG and MMFC since the resonant wavelengths of the LPFG and MMFC will shift in opposite directions when the surrounding RI changes. Experimental results show that the sensor possesses an enhanced sensitivity of 526.92nm/RIU in the RI range of 1.387-1.394 RIU. The response to the temperature is also discussed.展开更多
The high degree of freedom and novel nonlinear phenomena of multimode fiber are attracting attention. In this work,we demonstrate a spatiotemporal mode-locked multimode fiber laser, which relies on microfiber knot res...The high degree of freedom and novel nonlinear phenomena of multimode fiber are attracting attention. In this work,we demonstrate a spatiotemporal mode-locked multimode fiber laser, which relies on microfiber knot resonance(MKR) via dissipative four-wave-mixing(DFMW) to achieve high-repetition-rate pulses. Apart from that, DFMW mode locking with switchable central wavelengths can also be obtained. It was further found that high pulse energy induced nonlinear effect of the dominant mode-locking mechanism transforming from DFMW to nonlinear Kerr beam cleaning effect(NL-KBC). The experimental results are valuable for further comprehending the dynamic characteristics of spatiotemporal mode-locked multimode fiber lasers, facilitating them much more accessible for applications.展开更多
The structure of an intensity modulation optical fiber sensor is introduced. The principle of the sensor which can detect minor displacement by use of minor curve in dark ground is described. Complex experiment shows ...The structure of an intensity modulation optical fiber sensor is introduced. The principle of the sensor which can detect minor displacement by use of minor curve in dark ground is described. Complex experiment shows that the multimode optical fiber not only has the abilitly of detecting the displacement of less than 0.1 nm, but also exhibits characteristics of wide dynamic range and good linearety.展开更多
As an annual calendar event, China’s International Man-made Fiber Conference sets out, as always as it started over 20 years ago, to provide an international platform at its 13th International Conference for technica...As an annual calendar event, China’s International Man-made Fiber Conference sets out, as always as it started over 20 years ago, to provide an international platform at its 13th International Conference for technical exchange and cooperation in an effort to direct Chinese MMF’s future roadmap. Mr. Zheng Zhiyi, President of China Chemical Fiber Association (CCFA), will roll out a technological tracking back into the past, and technological forecast back into the future, showing his determination in encouraging science and technology to play a contributive major role in beefing up the chemical fiber industry in China.展开更多
The detection of the state of polarization(SOP)of light is essential for many optical applications.However,cost-effective SOP measurement is a challenge due to the complexity of conventional methods and the poor trans...The detection of the state of polarization(SOP)of light is essential for many optical applications.However,cost-effective SOP measurement is a challenge due to the complexity of conventional methods and the poor transferability of new methods.We propose a straightforward,low-cost,and portable SOP measurement system based on the multimode fiber speckle.A convolutional neural network is utilized to establish the mapping relationship between speckle and Stokes parameters.The lowest root-mean-square error of the estimated SOP on the Poincarésphere can be 0.0042.This method is distinguished by its low cost,clear structure,and applicability to different wavelengths with high precision.The proposed method is of great value in polarization-related applications.展开更多
A piece of multimode optical fiber with a low num er ical aperture (NA) is used as an inexpensive microlens to collimate the output r adiation of a laser diode bar in the high numerical aperture (NA) direction.The em...A piece of multimode optical fiber with a low num er ical aperture (NA) is used as an inexpensive microlens to collimate the output r adiation of a laser diode bar in the high numerical aperture (NA) direction.The emissions of the laser diode bar are coupled into multimode fiber array.The radi ation from individual ones of emitter regions is optically coupled into individu al ones of fiber array.Total coupling efficiency and fiber output power are 75% and 15W,respectively.展开更多
Wavefront shaping(WFS)techniques have been used as a powerful tool to control light propagation in complex media,including multimode fibers.In this paper,we propose a new application of WFS for multimode fber-based se...Wavefront shaping(WFS)techniques have been used as a powerful tool to control light propagation in complex media,including multimode fibers.In this paper,we propose a new application of WFS for multimode fber-based sensors.The use of a single multimode fiber alone,without any special fabrication,as a sensor based on the light intensity variations is not an easy task.The twist effect on multimode fiber is used as an example herein.Experimental results show that light intensity through the multimode fiber shows no direct relationship with the twist angle,but the correlation coefficient(CC)of speckle patterns does.Moreover,if WFS is applied to transform the spatially seemingly random light pattern at the exit of the multimode fiber into an optical focus.The focal pattern correlation and intensity both can serve to gauge the twist angle,with doubled measurement range and allowance of using a fast point detector to provide the feedback.With further development,WFS may find potentials to facilitate the development of multimode fber-based sensors in a variety of scenarios.展开更多
The interference of selective higher-order modes in optical fibers is investigated both theoretically and experimentally. It has been demonstrated that by coupling the LP01 mode in a step-index single-mode fiber (SMF)...The interference of selective higher-order modes in optical fibers is investigated both theoretically and experimentally. It has been demonstrated that by coupling the LP01 mode in a step-index single-mode fiber (SMF) to the LP0m modes in step-index multimode fibers (MMFs) with different parameters, one can selectively generate higher-order modes and construct all-fiber interferometers. The research presented in this paper forms a basis of a new type of fiber devices with potential applications in fiber sensing, optical fiber communications, and optical signal processing.展开更多
A magnetic field sensor with a magnetic fluid(MF)-coated intermodal interferometer is proposed and experimentally demonstrated. The interferometer is formed by sandwiching a segment of single mode fiber(SMF) between a...A magnetic field sensor with a magnetic fluid(MF)-coated intermodal interferometer is proposed and experimentally demonstrated. The interferometer is formed by sandwiching a segment of single mode fiber(SMF) between a segment of multi-mode fiber(MMF) and a spherical structure. It can be considered as a cascade of the traditional SMF-MMF-SMF structure and MMF-SMF-sphere structure. The transmission spectral characteristics change with the variation of applied magnetic field. The experimental results exhibit that the magnetic field sensitivities for wavelength and transmission loss are 0.047 nm/m T and 0.215 d B/m T for the interference dip around 1 535.36 nm. For the interference dip around 1548.41 nm,the sensitivities are 0.077 nm/m T and 0.243 d B/m T. Simultaneous measurement can be realized according to the different spectral responses.展开更多
基金financial supports from the National Natural Science Foundation of China (62075132 and 92050202)Natural Science Foundation of Shanghai (22ZR1443100)
文摘This work introduces special states for light in multimode fibers featuring strongly enhanced or reduced correlations be-tween output fields in the presence of environmental temperature fluctuations.Using experimentally measured multi-tem-perature transmission matrix,a set of temperature principal modes that exhibit resilience to disturbances caused by tem-perature fluctuations can be generated.Reversing this concept also allows the construction of temperature anti-principal modes,with output profiles more susceptible to temperature influences than the unmodulated wavefront.Despite changes in the length of the multimode fiber within the temperature-fluctuating region,the proposed approach remains capable of robustly controlling the temperature response within the fiber.To illustrate the practicality of the proposed spe-cial state,a learning-empowered fiber specklegram temperature sensor based on temperature anti-principal mode sensi-tization is proposed.This sensor exhibits outstanding superiority over traditional approaches in terms of resolution and accuracy.These novel states are anticipated to have wide-ranging applications in fiber communication,sensing,imaging,and spectroscopy,and serve as a source of inspiration for the discovery of other novel states.
基金supported by National Natural Science Foundation of China(62135007 and 61925502).
文摘Optical endoscopy has become an essential diagnostic and therapeutic approach in modern biomedicine for directly observing organs and tissues deep inside the human body,enabling non-invasive,rapid diagnosis and treatment.Optical fiber endoscopy is highly competitive among various endoscopic imaging techniques due to its high flexibility,compact structure,excellent resolution,and resistance to electromagnetic interference.Over the past decade,endoscopes based on a single multimode optical fiber(MMF)have attracted widespread research interest due to their potential to significantly reduce the footprint of optical fiber endoscopes and enhance imaging capabilities.In comparison with other imaging principles of MMF endoscopes,the scanning imaging method based on the wavefront shaping technique is highly developed and provides benefits including excellent imaging contrast,broad applicability to complex imaging scenarios,and good compatibility with various well-established scanning imaging modalities.In this review,various technical routes to achieve light focusing through MMF and procedures to conduct the scanning imaging of MMF endoscopes are introduced.The advancements in imaging performance enhancements,integrations of various imaging modalities with MMF scanning endoscopes,and applications are summarized.Challenges specific to this endoscopic imaging technology are analyzed,and potential remedies and avenues for future developments are discussed.
文摘A respiratory monitoring system was proposed based on optical fiber.The sensor consists of photonic crystal fiber(PCF)spliced with multimode fiber(MMF)to fabricate Michelson interferometer.The sensor is inserted into an oxygen mask tube and then put on the nose and mouth to monitor the respiratory rate(RR)for different cases.The results showed that when breathing increased,the intensity of light decreased.The intensity of light in the sleeping case of breathing was more intense than that when the intensity of working sport was measured.The working sport case was a higher transmittance than that of sleeping.The sensitivity of the sensor was also measured to be 231.9 pm/RH.
基金supported by the National Key Research and Development Program of China(No.2017YFB0405600)the National Natural Science Foundation of China(Nos.62001326,61274113 and 61404091)+2 种基金the Natural Science Foundation of Tianjin City(Nos.18JCYBJC85700 and 18JCZDJC30500)the Open Project of State Key Laboratory of Functional Materials for Information(No.SKL202007)the Science and Technology Planning Project of Tianjin City(No.20ZYQCGX00070)。
文摘We proposed a compact and tunable multimode interferometer(MMI)based on an asymmetric wavy fiber(AMWF),which has axial offset,off-center taper waist,and micro-length.The fabrication process only contains non-axis pulling processes of single-mode fiber on two close positions.Theoretical qualitative analyses and experiments verify the tunable multimode propagation of the AMWF.Experimental results show a nonlinear wavelength response with increasing axis displacement from 0 to 120μm.In the range of 0—10μm,the sensitivity reaches the highest value of-1.33 nm/μm.Owing to its cost-effective,high-compact and tunable multimode propagation properties,the AMWF provides a promising platform for micro-nano photonic devices and optical sensing applications.
基金supported by the National Natural Science Foundation of China(Grant Nos.T2293751,T2293752,61735017,62020106002,and 62005250)the National Key Basic Research Program of China(Grant No.2021YFC2401403)the Major Scientific Research Project of Zhejiang Lab(Grant No.2019MC0AD02).
文摘Imaging through multimode fiber(MMF)provides high-resolution imaging through a fiber with cross section down to tens of micrometers.It requires interferometry to measure the full transmission matrix(TM),leading to the drawbacks of complicated experimental setup and phase instability.Reference-less TM retrieval is a promising robust solution that avoids interferometry,since it recovers the TM from intensity-only measurements.However,the long computational time and failure of 3D focusing still limit its application in MMF imaging.We propose an efficient reference-less TM retrieval method by developing a nonlinear optimization algorithm based on fast Fourier transform(FFT).Furthermore,we develop an algorithm to correct the phase offset error of retrieved TM using defocused intensity images and hence achieve 3D focusing.The proposed method is validated by both simulations and experiments.The FFT-based TM retrieval algorithm achieves orders of magnitude of speedup in computational time and recovers 2286×8192 TM of a 0.22 NA and 50μm diameter MMF with 112.9 s by a computer of 32 CPU cores.With the advantages of efficiency and correction of phase offset,our method paves the way for the application of reference-less TM retrieval in not only MMF imaging but also broader applications requiring TM calibration.
基金supported by the National Natural Science Foundation of China(NSFC)(Grant No.81930048)the Hong Kong Innovation and Technology Commission(Grant Nos.GHP/043/19SZ and GHP/044/19GD)+3 种基金the Hong Kong Research Grant Council(Grant Nos.15217721,R5029-19 and C7074-21GF)the Guangdong Science and Technology Commission(Grant No.2019BT02X105)the Shenzhen Science and Technology Innovation Commission(Grant No.JCYJ20220818100202005)the Hong Kong Polytechnic University(Grant Nos.P0038180,P0039517,P0043485 and P0045762).
文摘Transmission matrix(TM)allows light control through complex media,such as multimode fibers(MMFs),gaining great attention in areas,such as biophotonics,over the past decade.Efforts have been taken to retrieve a complex-valued TM directly from intensity measurements with several representative phase-retrieval algorithms,which still see limitations of slow or suboptimum recovery,especially under noisy environments.Here,we propose a modified nonconvex optimization approach.Through numerical evaluations,it shows that the optimum focusing efficiency is approached with less running time or sampling ratio.The comparative tests under different signal-to-noise levels further indicate its improved robustness.Experimentally,the superior focusing performance of our algorithm is collectively validated by single-and multispot focusing;especially with a sampling ratio of 8,it achieves a 93.6%efficiency of the gold-standard holography method.Based on the recovered TM,image transmission through an MMF is realized with high fidelity.Due to parallel operation and GPU acceleration,our nonconvex approach retrieves a 8685×1024 TM(sampling ratio is 8)with 42.3 s on average on a regular computer.The proposed method provides optimum efficiency and fast execution for TM retrieval that avoids the need for an external reference beam,which will facilitate applications of deep-tissue optical imaging,manipulation,and treatment.
基金supported by the National Natural Science Foundation of China (Grant Nos. 11274181,10974100,and 10674075)the Tianjin Key Program of Application Foundations and Future Technology Research Project,China (Grant No. 10JCZDJC24300)the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20120031110033)
文摘A novel tunable comb filter composed of a single-mode/multimode/polarization-maintaining-fiber-based Sagnac fiber loop is proposed and experimentally demonstrated. The filter tunability is achieved by rotating the polarization controller. The spectral shift is dependent on rotation direction and the position of the polarization controller. In addition, the adjustable range achieved by rotating the half-wave-plate polarization controller is twice higher than that of the quarter-wave-plate one.
基金supported in part by the National Natural Foundation of China(Nos. 61875086, 61377086)the Aerospace Science Foundation of China (No.2016ZD52042)Nanjing University of Aeronautics and Astronautics Ph. D. short-term visiting scholar project (No.190901DF08)
文摘We propose the trench-assisted multimode fiber(TA-OM4)as a novel sensing fiber in forward Brillouin scattering(FBS)-based temperature sensor,due to its higher temperature sensitivity,better bending resistance and lower propagation loss,compared with the single mode fiber(SMF)and other sensing fibers.The FBS effect and acousto-optic interaction in TA-OM4 are the first time to be demonstrated and characterized at 1550 nm theoretically and experimentally.A 2.0 km long TA-OM4 is put into an oven to measure its temperature sensitivity,which can reach up to 80.3 kHz/℃,exceeding 53%of SMF(52.4 kHz/℃).The simulated and experimental results verify that the TA-OM4 may be a good candidate as the sensing fiber for the FBS-based temperature sensor.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.12074331,61875238,and 61971373)the Natural Science Foundation of Hebei Province,China(Grant Nos.F2021203002,F2019203549,and F2020203050)the Science and Technology Support Projects of Research and Development Plans of Qinhuangdao City(Grant No.202004A001).
文摘We numerically investigate the mid-infrared(MIR)supercontinuum(SC)and SC-based optical frequency comb(OFC)generations when the three optical modes(LP_(01),LP_(02),and LP_(12))are considered in a multimode tellurite photonic crystal fiber(MM-TPCF).The geometrical parameters of the MM-TPCF are optimized to support the multimode propagation and obtain the desired dispersion characteristics of the considered three optical modes.When the pump pulse with center wavelengthλ=2.5μm,width T=80 fs,and peak power P=18 kW is coupled into the anomalous dispersion region of the LP_(01),LP_(02),and LP_(12)modes of the MM-TPCF,the-40-dB bandwidth of the generated MIR SCs can be up to 2.56,1.39,and 1.12 octaves,respectively,along with good coherence.Moreover,the nonlinear dynamics of the generated SCs are analyzed.Finally,the MIR SCs-based OFCs are demonstrated when a train of 50 pulses at 1-GHz repetition rate is used as the pump source and launched into the MM-TPCF.
基金Supported by the National Natural Science Foundation of China under Grant Nos 61327012 and 61505160the Natural Science Foundation of Shaanxi Province under Grant No 2016JQ6021the Shaanxi Key Laboratory of Optical Information Technology under Grant No OIT201601
文摘A refractive index （RI） sensor based on hybrid long-period fiber grating （LPFG） with multimode fiber core （MMFC） is proposed and demonstrated. The surrounding RI can be determined by monitoring the separation between the resonant wavelengths of the LPFG and MMFC since the resonant wavelengths of the LPFG and MMFC will shift in opposite directions when the surrounding RI changes. Experimental results show that the sensor possesses an enhanced sensitivity of 526.92nm/RIU in the RI range of 1.387-1.394 RIU. The response to the temperature is also discussed.
基金Project partially supported by the National Natural Science Foundation of China (Grant Nos. 91950105 and 62175116)the 1311 Talent Plan of Nanjing University of Posts and Telecommunications。
文摘The high degree of freedom and novel nonlinear phenomena of multimode fiber are attracting attention. In this work,we demonstrate a spatiotemporal mode-locked multimode fiber laser, which relies on microfiber knot resonance(MKR) via dissipative four-wave-mixing(DFMW) to achieve high-repetition-rate pulses. Apart from that, DFMW mode locking with switchable central wavelengths can also be obtained. It was further found that high pulse energy induced nonlinear effect of the dominant mode-locking mechanism transforming from DFMW to nonlinear Kerr beam cleaning effect(NL-KBC). The experimental results are valuable for further comprehending the dynamic characteristics of spatiotemporal mode-locked multimode fiber lasers, facilitating them much more accessible for applications.
文摘The structure of an intensity modulation optical fiber sensor is introduced. The principle of the sensor which can detect minor displacement by use of minor curve in dark ground is described. Complex experiment shows that the multimode optical fiber not only has the abilitly of detecting the displacement of less than 0.1 nm, but also exhibits characteristics of wide dynamic range and good linearety.
文摘As an annual calendar event, China’s International Man-made Fiber Conference sets out, as always as it started over 20 years ago, to provide an international platform at its 13th International Conference for technical exchange and cooperation in an effort to direct Chinese MMF’s future roadmap. Mr. Zheng Zhiyi, President of China Chemical Fiber Association (CCFA), will roll out a technological tracking back into the past, and technological forecast back into the future, showing his determination in encouraging science and technology to play a contributive major role in beefing up the chemical fiber industry in China.
基金supported by the National Key Research and Development Program of China(Grant No.2021YFB2800902)the National Natural Science Foundation of China(Grant No.62225110)+1 种基金the Key Research and Development Program of Hubei Province(No.2022BAA001)the Innovation Fund of WNLO.
文摘The detection of the state of polarization(SOP)of light is essential for many optical applications.However,cost-effective SOP measurement is a challenge due to the complexity of conventional methods and the poor transferability of new methods.We propose a straightforward,low-cost,and portable SOP measurement system based on the multimode fiber speckle.A convolutional neural network is utilized to establish the mapping relationship between speckle and Stokes parameters.The lowest root-mean-square error of the estimated SOP on the Poincarésphere can be 0.0042.This method is distinguished by its low cost,clear structure,and applicability to different wavelengths with high precision.The proposed method is of great value in polarization-related applications.
文摘A piece of multimode optical fiber with a low num er ical aperture (NA) is used as an inexpensive microlens to collimate the output r adiation of a laser diode bar in the high numerical aperture (NA) direction.The emissions of the laser diode bar are coupled into multimode fiber array.The radi ation from individual ones of emitter regions is optically coupled into individu al ones of fiber array.Total coupling efficiency and fiber output power are 75% and 15W,respectively.
基金supported by the Shenzhen Science and Technology Innovation Commission(No.JCYJ20170818104421564)the Hong Kong Innovation and Technology Commission(No.ITS/022/18)+1 种基金the Hong Kong Research Grant Council(No.25204416)the National Natural Science Foundation of China(Nos.81671726 and 81627805).
文摘Wavefront shaping(WFS)techniques have been used as a powerful tool to control light propagation in complex media,including multimode fibers.In this paper,we propose a new application of WFS for multimode fber-based sensors.The use of a single multimode fiber alone,without any special fabrication,as a sensor based on the light intensity variations is not an easy task.The twist effect on multimode fiber is used as an example herein.Experimental results show that light intensity through the multimode fiber shows no direct relationship with the twist angle,but the correlation coefficient(CC)of speckle patterns does.Moreover,if WFS is applied to transform the spatially seemingly random light pattern at the exit of the multimode fiber into an optical focus.The focal pattern correlation and intensity both can serve to gauge the twist angle,with doubled measurement range and allowance of using a fast point detector to provide the feedback.With further development,WFS may find potentials to facilitate the development of multimode fber-based sensors in a variety of scenarios.
文摘The interference of selective higher-order modes in optical fibers is investigated both theoretically and experimentally. It has been demonstrated that by coupling the LP01 mode in a step-index single-mode fiber (SMF) to the LP0m modes in step-index multimode fibers (MMFs) with different parameters, one can selectively generate higher-order modes and construct all-fiber interferometers. The research presented in this paper forms a basis of a new type of fiber devices with potential applications in fiber sensing, optical fiber communications, and optical signal processing.
基金supported by the National Natural Science Foundation of China(No.61475118)the National High-Tech Research and Development Program of China(863 Program)(No.2013AA014201)the Opened Fund of the State Key Laboratory on Integrated Optoelectronics(No.IOSKL2015KF06)
文摘A magnetic field sensor with a magnetic fluid(MF)-coated intermodal interferometer is proposed and experimentally demonstrated. The interferometer is formed by sandwiching a segment of single mode fiber(SMF) between a segment of multi-mode fiber(MMF) and a spherical structure. It can be considered as a cascade of the traditional SMF-MMF-SMF structure and MMF-SMF-sphere structure. The transmission spectral characteristics change with the variation of applied magnetic field. The experimental results exhibit that the magnetic field sensitivities for wavelength and transmission loss are 0.047 nm/m T and 0.215 d B/m T for the interference dip around 1 535.36 nm. For the interference dip around 1548.41 nm,the sensitivities are 0.077 nm/m T and 0.243 d B/m T. Simultaneous measurement can be realized according to the different spectral responses.
