A fiber twist sensor using a Sagnac interferometer incorporating a tapered polarization-maintaining fiber(PMF)is proposed.The transmission properties of the sensor are investigated both theoretically and experimentall...A fiber twist sensor using a Sagnac interferometer incorporating a tapered polarization-maintaining fiber(PMF)is proposed.The transmission properties of the sensor are investigated both theoretically and experimentally.Given the optoelastic effect,which depends on fiber geometry,the modal and group birefringences of the PMF can be controlled by applying different twist angles.The spectral wavelength shifts,free spectral ranges,and transmission losses of the original,microtapered,and etched PMFs were compared.Notably,the interference dips for the etched PMF move in opposite directions.As a result,the proposed PMF-based sensor could have multiparameter sensing applications.展开更多
We demonstrate a self-started,long-term stable polarization-maintaining mode-locked fiber laser based on the nonlinear polarization evolution technique.A polarized beam splitter is inserted into the cavity of the line...We demonstrate a self-started,long-term stable polarization-maintaining mode-locked fiber laser based on the nonlinear polarization evolution technique.A polarized beam splitter is inserted into the cavity of the linear polarizationmaintaining fiber laser to facilitate self-started mode-locking.Pulses with single pulse energy of 26.9 nJ and average output power of 73.9 mW are obtained at the pump power of 600 mW.The transmission characteristics of artificial saturable absorber used in this laser are analyzed theoretically,the influence of the half-wave plate state on mode-locking is discussed,and the mode-locking range is obtained,which is well consistent with the experimental results.展开更多
We present a high-power, high-stability all-polarization-maintaining(all-PM) fiber femtosecond pulse laser source at 780 nm with full engineering integration that comprises an all-PM fiber amplified chirped pulse lase...We present a high-power, high-stability all-polarization-maintaining(all-PM) fiber femtosecond pulse laser source at 780 nm with full engineering integration that comprises an all-PM fiber amplified chirped pulse laser at 1560 nm, a grating pair compressor and a second-harmonic generation(SHG) module. The all-PM fiber amplified chirped pulse laser at 1560 nm operates with a repetition rate of 111.5 MHz and an average power of 5.37 W, which is compressed with a pulse width of about 204 fs. The 780-nm pulses are subsequently generated by SHG in a frequency-doubling crystal. We achieve an average power of 2.22 W at 780 nm with a pulse width of 288 fs, a SHG efficiency of 52%, and a root-mean-square power fluctuation of 0.23%, which is the best performance merit as far as we know. The whole laser system is finally integrated for practical applications with reliable laser operation. We anticipate that this 780-nm all-PM fiber femtosecond pulse laser with full engineering integration is promising for frontier applications such as two-photon imaging, nanofabrication, terahertz generation, etc.展开更多
An all-fiber polarization maintaining high-power laser system operating at 1.7 μm based on the Ramaninduced soliton self-frequency shifting effect is demonstrated. The entirely fiberized system is built by erbiumdope...An all-fiber polarization maintaining high-power laser system operating at 1.7 μm based on the Ramaninduced soliton self-frequency shifting effect is demonstrated. The entirely fiberized system is built by erbiumdoped oscillator and two-stage amplifiers with polarization maintaining commercial silica fibers and devices, which can provide robust and stable soliton generation. High-power soliton laser with the average power of 0.28 W,the repetition rate of 42.7 MHz, and pulse duration of 515 fs is generated directly from the main amplifier.Our experiment provides a feasible method for high-power all-fiber polarization maintaining femtosecond laser generation working at 1.7 μm.展开更多
Mid-infrared wavelength switchable and dual-wavelength random laser output has many potential applications.A polarization-maintaining random fiber Bragg grating(PMRFBG)array based on the photonic localization effect o...Mid-infrared wavelength switchable and dual-wavelength random laser output has many potential applications.A polarization-maintaining random fiber Bragg grating(PMRFBG)array based on the photonic localization effect of longitudinal invariant transverse disorder in fiber structure is proposed,which can be used as random feedback of dual-wavelength and wavelength switchable output of random fiber laser(RFL).The random fiber Bragg grating(RFBG)array was designed on the panda-type polarization-maintaining fiber(PMF),and the two center wavelengths were 2151.60 nm and 2152.22 nm,respectively.The RFBG array was designed on the bow tie-type PMF,and the two center wavelengths were obtained,which were 2153.08 nm and 2153.96 nm,respectively.The RFBG array with a center wavelength of 2139.27 nm was designed on single-mode fiber(SMF).The length of individual fiber Bragg grating(FBG)and PMRFBG,the refractive index modulation depth,the number of cascaded gratings,and the distance between gratings have different effects on the full width at half maximum(FWHM)and reflectance of the RFBG and PMRFBG array,but not on the central wavelength,as obtained by simulation using the transmission matrix method.The designed PMRFBG array provides theoretical support for the design of the feedback mechanism of RFL.展开更多
A novel polarization maintaining fiber （PMF） loop is proposed and used for an interferometric fiber optic gyroscope （FOG）. By splicing a conventional PMF loop with two pigtailed polarization beam splitters, polari...A novel polarization maintaining fiber （PMF） loop is proposed and used for an interferometric fiber optic gyroscope （FOG）. By splicing a conventional PMF loop with two pigtailed polarization beam splitters, polarized light can be guided to propagate along the slow and fast axes of the PMF in sequence to double its effective optical length in the loop. In particular, the resultant optical length in the combined loop is partially self-compensated for some external disturbances, such as transverse strain. Primary experiments on the FOG using the proposed loop demonstrate that the average static bias deviation between-40 and ＋60 °C is less than 0.050 deg./h, and the average bias variation under conventional random vibration test is less than 0.10 deg./h.展开更多
An environmentally stable, repetition rate tunable, all-polarization-maintaining, Er-doped pulse fiber laser with a single-wall carbon nanotubes saturated absorber is demonstrated. The ring laser cavity includes a del...An environmentally stable, repetition rate tunable, all-polarization-maintaining, Er-doped pulse fiber laser with a single-wall carbon nanotubes saturated absorber is demonstrated. The ring laser cavity includes a delay line enabling a tunable repetition rate to vary from 35.52 MHz to 35.64 MHz with continuous mode-locked operation. The laser output parameters confirm that the tunable mode-locked operations are stable. High environmental stability is also confirmed by the -130 dBc/Hz low phase noise, a 70-dB signal-to-noise ratio of radio frequency signals, a low amplitude fluctuation of 5.76 × 10-4, and a low fluctuation of reoetition rate of 12 Hz. The laser shows a high de^ree of oolarization of 93%.展开更多
A low-repetition-rate, all-polarization-maintaining（PM）-fiber sub-nanosecond oscillator is presented, which is simple and low-cost, composed of standard components. The ring cavity is elongated by 114-m-long standar...A low-repetition-rate, all-polarization-maintaining（PM）-fiber sub-nanosecond oscillator is presented, which is simple and low-cost, composed of standard components. The ring cavity is elongated by 114-m-long standard PM fiber, and passively mode-locked by a fiber pigtailed semiconductor saturable absorber. Linearly polarized pulses with 1.66 MHz repetition rate and 22 dB polarization extinction ratio are generated at a wavelength of 1030 nm, which is determined by an intracavity filter. In addition, to demonstrate that the oscillator is a good seed for high energy pulse generation, an all-fiber master oscillator power amplifier is built and amplified pulses with energy about 2 μJ are obtained.展开更多
A novel type of sampled fiber Bragg gratings （FBGs） written in polarization-maintaining fiber （PMF） is proposed. The reflection spectrum, time delay, and group velocity dispersion （GVD） of the gratings are analy...A novel type of sampled fiber Bragg gratings （FBGs） written in polarization-maintaining fiber （PMF） is proposed. The reflection spectrum, time delay, and group velocity dispersion （GVD） of the gratings are analyzed. In addition, the reflection spectrum is optimized by apodization. The scheme of multi-wavelength output based on the gratings is proposed, which could be used as a multi-wavelength polarization filter in the density wavelength division multiplexed （DWDM） system.展开更多
We demonstrated the~2.8-μm and~3.5-μm linearly polarized continuous wave(CW)laser outputs from a polarization-maintaining(PM)Er^(3+)-doped fluoride fiber laser.By introducing a film polarizer into the cavity to sele...We demonstrated the~2.8-μm and~3.5-μm linearly polarized continuous wave(CW)laser outputs from a polarization-maintaining(PM)Er^(3+)-doped fluoride fiber laser.By introducing a film polarizer into the cavity to select the laser polarization orientation,the~2.8-μm linearly polarized CW laser with a high polarization extinction ratio(PER)of~23 dB and maximum output power of 2.37 W was achieved under double-end pumping at 976 nm.By adding another 1981-nm pump source simultaneously,the~3.5-μm linearly polarized CW laser was also obtained,giving higher PER of~27 dB and maximum output power of 307 mW which is only limited by the available power of 1981-nm pump.To the best of our knowledge,this is the first report on a mid-infrared linearly polarized CW PM fiber laser in the>2.5-μm mid-infrared region.This work not only opens up opportunities for some new mid-infrared applications,but also provides a promising platform for developing high-stability and versatile mid-infrared laser sources.展开更多
We report on a novel architecture to suppress the multi-pulse formation in an all-polarization-maintaining figure-9 erbium-doped fiber laser under high pump power. A 2×2 fiber coupler is introduced into the phase...We report on a novel architecture to suppress the multi-pulse formation in an all-polarization-maintaining figure-9 erbium-doped fiber laser under high pump power. A 2×2 fiber coupler is introduced into the phase-biased nonlinear amplifying loop mirror to extract part of intracavity laser power as a laser output, and the dependence of output couple ratio of fiber coupler on the mode-locking state is experimentally investigated. The intracavity nonlinear effect is mitigated by lowering the intracavity laser power, which is conducive to avoiding the multi-pulse formation. In the meantime, the loss-imbalance induced by fiber coupler is helpful in improving the self-starting ability. With the proposed laser structure,the multiple pulse formation can be suppressed and high power single pulse train can be obtained. The laser emits three pulse trains which is convenient for some applications. Finally, the output power values of three ports are 5.3 m W, 51.3 m W,and 13.2 m W, respectively. The total single pulse output power is 69.8 m W, which is more than 10 times the result without OC2. The total slope efficiency is about 10.1%. The repetition rate of three pulse trains is 21.17 MHz, and the pulse widths are 2.8 ps, 2.63 ps, and 6.66 ps, respectively.展开更多
We present the generation of wavelength-switchable single-polarization solitons in an all-polarization-maintaining erbium-doped fiber laser mode-locked by a graphene saturable absorber. Ultrashort pulses centered at t...We present the generation of wavelength-switchable single-polarization solitons in an all-polarization-maintaining erbium-doped fiber laser mode-locked by a graphene saturable absorber. Ultrashort pulses centered at the wavelength of 1531.6 nm with the duration of 816 fs and centered at the wavelength of 1557.8 nm with the duration of 402 fs are separately obtained from the same fiber laser cavity. The cavity loss adjusted by the gold reflector plays a crucial role in wavelength switching.展开更多
Long-period fiber gratings have the advantages of small size,corrosion resistance,anti-electro-magnetic interference,and high sensitivity,making them widely used in biomedicine,the power industry,and aerospace.This pa...Long-period fiber gratings have the advantages of small size,corrosion resistance,anti-electro-magnetic interference,and high sensitivity,making them widely used in biomedicine,the power industry,and aerospace.This paper develops a long-period fiber grating sensor based on periodic microchannels.First,a series of linear structures were etched in the cladding of a single-mode fiber by femtosecond laser microma-chining.Then,the laser-modified region was selectively eroded by selective chemical etching to obtain the periodic microchannel structure.Finally,the channels were filled with polydimethylsiloxane(PDMS)to im-prove the spectral quality.The experimental results show that the sensor has good sensitivity in the measure-ment of various parameters such as temperature,stress,refractive index(RI),and bending.It has a temperat-ure sensitivity of−55.19 pm/℃,a strain sensitivity of−3.19 pm/με,a maximum refractive index sensitivity of 540.28 nm/RIU,and a bending sensitivity of 2.65 dB/m^(-1).All of the measurement parameters show good lin-ear responses.The sensor has strong application prospects in the field of precision measurement and sensing.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
The heavily germanium(Ge)-doped silica fiber assisted by two air holes in the cladding exhibits high nonlinearity and birefringence,low loss and normal group velocity dispersion(GVD)for two fundamental modes(FMs).When...The heavily germanium(Ge)-doped silica fiber assisted by two air holes in the cladding exhibits high nonlinearity and birefringence,low loss and normal group velocity dispersion(GVD)for two fundamental modes(FMs).When the 1920 nm and 0.1 ps pump pulse with 100 kW peak power is coupled into the 0.5-m-long fiber and polarized along one of two principle axes,the generated spectra can cover the wavelength range around 1000—2500 nm at-20 dB.Furthermore,the output pulse has an excellent coherence in the whole wavelength range.展开更多
This paper examines the design and optimization of optical fibers for high-speed data transmission, emphasizing advancements that maximize efficiency in modern communication networks. Optical fibers, core components o...This paper examines the design and optimization of optical fibers for high-speed data transmission, emphasizing advancements that maximize efficiency in modern communication networks. Optical fibers, core components of global communication infrastructure, are capable of transmitting data over long distances with minimal loss through principles like total internal reflection. This study explores single-mode and multi-mode fiber designs, providing an overview of key parameters such as core diameter, refractive index profile, and numerical aperture. Mathematical modeling using Maxwell’s equations plays a central role in optimizing fiber performance, helping engineers mitigate challenges like attenuation and dispersion. The paper also discusses advanced techniques, including dense wavelength division multiplexing (DWDM), which enables terabit-per-second data rates. Case studies in practical applications, such as fiber-to-the-home (FTTH) networks and transoceanic cables, highlight the impact of optimized designs on network performance. Looking forward, innovations in photonic crystal fibers and hollow-core fibers are expected to drive further improvements, enabling ultra-high-speed data transmission. The paper concludes by underscoring the significance of continuous research and development to address challenges in optical fiber technology and support the increasing demands of global communication systems.展开更多
Road construction in Africa is faced with a shortage of quality materials, leading to delays and increased costs. Traditional materials, such as clay soils of the bar soil type, have inadequate properties for pavement...Road construction in Africa is faced with a shortage of quality materials, leading to delays and increased costs. Traditional materials, such as clay soils of the bar soil type, have inadequate properties for pavement sub-base layers, particularly in terms of bearing capacity. This study explores a composite material combining bar soil and bamboo fibers to improve the mechanical performance of bar soil, offering a sustainable and cost-effective solution. The Tori-Bossito bar soil was characterised by particle size analysis, Atterberg limits, Proctor compaction tests and the California Bearing Ratio (CBR). The results show that this material is a class A2 sandy-clay soil with a CBR of 18, which is insufficient for foundation layers requiring a CBR of over 30. To improve its performance, Sèmè-Kpodji bamboo fibers, 30 to 100 microns in diameter and 3 to 5 cm long, were incorporated at rates of 0.9% to 2.7%. The optimum mix, with 2.4% fiber, has a CBR of 35, a dry density of 1.92 t/m3 and a moisture content of 12.4%. This reinforced material is suitable as a base course for low-traffic roadways.展开更多
Concrete buildings used in cold regions are prone to freeze-thaw damage, leading to internal cracking and surface peeling of the concrete. Therefore, improving the freeze-thaw resistance of concrete is of great signif...Concrete buildings used in cold regions are prone to freeze-thaw damage, leading to internal cracking and surface peeling of the concrete. Therefore, improving the freeze-thaw resistance of concrete is of great significance for the safety of hydraulic engineering. This paper explores the effect of basalt fibers on improving the frost resistance index of concrete through a series of experiments, and analyzes the influencing mechanism. The results show that adding an appropriate amount of basalt fibers can significantly improve the frost resistance of concrete and reduce the freeze-thaw damage phenomenon indicated by concrete specimens. Adding 0.1% basalt fiber can maintain the relative dynamic modulus of concrete specimens at 98% after 150 freeze-thaw cycles, while adding 0.3% basalt fiber can control the quality loss rate of concrete specimens after 150 freeze-thaw cycles at 0.87%. Taking into account both the frost resistance effect and economic factors, it is recommended that the basalt fiber content in frost resistant concrete be 0.1%. The research results can provide reference and guidance for the optimization design of the mix proportion of hydraulic concrete in cold regions.展开更多
Jute is the golden fiber crop of Bangladesh. Viral and Nemic diseases are the major threats to fiber crops, and the fiber yield decreases drastically as the disease infection increases. An experiment was conducted to ...Jute is the golden fiber crop of Bangladesh. Viral and Nemic diseases are the major threats to fiber crops, and the fiber yield decreases drastically as the disease infection increases. An experiment was conducted to screen and evaluate ten Jute and allied fiber varieties i.e. BJRI Kenaf-4, BJRI Kenaf-3, HS-95 (Kenaf), HS-24 (Mesta pat), HC-2 (Kenaf), BJRI Deshi pat-8, BJRI Deshi pat-7, BJRI Deshi pat-5, BJRI Deshi pat-6 and CVL-1 against mosaic virus and root-knot nematode disease. It was done in RCBD design with three replications at Sher-e-Bangla Agricultural University (SAU) central farm, Dhaka-1207, from June 2018 to March 2019. In the case of viral infection, variety 4 (HS-24 (Mesta pat)) showed maximum virus incidence (23.11%), whereas variety 2 (BJRI Kenaf-3) had no virus evidence. The most susceptible nematode-infected variety was found in varieties 5 (HC-2 (Kenaf)) and 9 (BJRI Deshi pat-6), which showed 80% incidence, whereas variety 2 (BJRI Kenaf-3) was highly resistance. The growth and yield results showed a significant (0.05%) reduction of plant height (cm) and fiber weight (t/ha) with an increase in the percentage of virus and nematode incidence against all varieties. The highest fiber weight (1.47 t/ha) and the lowest viral (0%) and nemic infection (0%) were found in variety 2 (BJRI Kenaf-3), which showed better performance compared to other varieties. These results revealed that variety 2 (BJRI Kenaf-3) had the best variety in the present study.展开更多
Bangladesh’s thriving okra cultivation sector annually yields substantial harvests, yet a significant portion of the plant remains underutilized after harvesting, posing as agricultural waste. This oversight neglects...Bangladesh’s thriving okra cultivation sector annually yields substantial harvests, yet a significant portion of the plant remains underutilized after harvesting, posing as agricultural waste. This oversight neglects the economic potential of okra fiber, which is versatile and valuable across various industries. This paper explores this untapped potential by investigating the physico-mechanical properties, chemical treatments, and fabrication techniques of okra fiber, drawing from a wealth of research. Comparative analyses with established natural fibers like jute and sisal shed light on okra fiber’s transformative role in Bangladesh’s economic landscape. Along with the applications in the fashion world, meticulous investigation into its mechanical, thermal, and morphological characteristics uncovers inherent strengths and integration pathways into industrial applications. Strategies for optimizing yield and quality, including novel approaches like photo-grafting and protein extraction, are explored. Considerations for cytotoxicity and environmental sustainability ensure its viability as a green resource. This research aims to unlock okra fiber’s full potential, positioning Bangladesh for sustainable economic development and innovation.展开更多
基金the National Natural Science Foundation of China(Grant Nos.11804171,11674177,and 61775107)partly by the Natural Science Foundation of Tianjin,China(Grant No.16JCZDJC31000)partly by the Self-Made Experiment Teaching Instrument Project of Nankai University 2018(Grant No.2018NKZZYQ04).
文摘A fiber twist sensor using a Sagnac interferometer incorporating a tapered polarization-maintaining fiber(PMF)is proposed.The transmission properties of the sensor are investigated both theoretically and experimentally.Given the optoelastic effect,which depends on fiber geometry,the modal and group birefringences of the PMF can be controlled by applying different twist angles.The spectral wavelength shifts,free spectral ranges,and transmission losses of the original,microtapered,and etched PMFs were compared.Notably,the interference dips for the etched PMF move in opposite directions.As a result,the proposed PMF-based sensor could have multiparameter sensing applications.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61575011 and 61975003)the Beijing Natural Science Foundation,China(Grant No.4192015).
文摘We demonstrate a self-started,long-term stable polarization-maintaining mode-locked fiber laser based on the nonlinear polarization evolution technique.A polarized beam splitter is inserted into the cavity of the linear polarizationmaintaining fiber laser to facilitate self-started mode-locking.Pulses with single pulse energy of 26.9 nJ and average output power of 73.9 mW are obtained at the pump power of 600 mW.The transmission characteristics of artificial saturable absorber used in this laser are analyzed theoretically,the influence of the half-wave plate state on mode-locking is discussed,and the mode-locking range is obtained,which is well consistent with the experimental results.
文摘We present a high-power, high-stability all-polarization-maintaining(all-PM) fiber femtosecond pulse laser source at 780 nm with full engineering integration that comprises an all-PM fiber amplified chirped pulse laser at 1560 nm, a grating pair compressor and a second-harmonic generation(SHG) module. The all-PM fiber amplified chirped pulse laser at 1560 nm operates with a repetition rate of 111.5 MHz and an average power of 5.37 W, which is compressed with a pulse width of about 204 fs. The 780-nm pulses are subsequently generated by SHG in a frequency-doubling crystal. We achieve an average power of 2.22 W at 780 nm with a pulse width of 288 fs, a SHG efficiency of 52%, and a root-mean-square power fluctuation of 0.23%, which is the best performance merit as far as we know. The whole laser system is finally integrated for practical applications with reliable laser operation. We anticipate that this 780-nm all-PM fiber femtosecond pulse laser with full engineering integration is promising for frontier applications such as two-photon imaging, nanofabrication, terahertz generation, etc.
基金Supported by the National Natural Science Foundation of China (Grant Nos. 10225417 and 61675009)the Natural Science Foundation of Beijing Municipality (Grant Nos. 4204091 and KZ201910005006)the China Postdoctoral Science Foundation (Grant No. 212423)。
文摘An all-fiber polarization maintaining high-power laser system operating at 1.7 μm based on the Ramaninduced soliton self-frequency shifting effect is demonstrated. The entirely fiberized system is built by erbiumdoped oscillator and two-stage amplifiers with polarization maintaining commercial silica fibers and devices, which can provide robust and stable soliton generation. High-power soliton laser with the average power of 0.28 W,the repetition rate of 42.7 MHz, and pulse duration of 515 fs is generated directly from the main amplifier.Our experiment provides a feasible method for high-power all-fiber polarization maintaining femtosecond laser generation working at 1.7 μm.
基金supported by the National Natural Science Foundation of China(Nos.52105540 and 51975044)。
文摘Mid-infrared wavelength switchable and dual-wavelength random laser output has many potential applications.A polarization-maintaining random fiber Bragg grating(PMRFBG)array based on the photonic localization effect of longitudinal invariant transverse disorder in fiber structure is proposed,which can be used as random feedback of dual-wavelength and wavelength switchable output of random fiber laser(RFL).The random fiber Bragg grating(RFBG)array was designed on the panda-type polarization-maintaining fiber(PMF),and the two center wavelengths were 2151.60 nm and 2152.22 nm,respectively.The RFBG array was designed on the bow tie-type PMF,and the two center wavelengths were obtained,which were 2153.08 nm and 2153.96 nm,respectively.The RFBG array with a center wavelength of 2139.27 nm was designed on single-mode fiber(SMF).The length of individual fiber Bragg grating(FBG)and PMRFBG,the refractive index modulation depth,the number of cascaded gratings,and the distance between gratings have different effects on the full width at half maximum(FWHM)and reflectance of the RFBG and PMRFBG array,but not on the central wavelength,as obtained by simulation using the transmission matrix method.The designed PMRFBG array provides theoretical support for the design of the feedback mechanism of RFL.
文摘A novel polarization maintaining fiber （PMF） loop is proposed and used for an interferometric fiber optic gyroscope （FOG）. By splicing a conventional PMF loop with two pigtailed polarization beam splitters, polarized light can be guided to propagate along the slow and fast axes of the PMF in sequence to double its effective optical length in the loop. In particular, the resultant optical length in the combined loop is partially self-compensated for some external disturbances, such as transverse strain. Primary experiments on the FOG using the proposed loop demonstrate that the average static bias deviation between-40 and ＋60 °C is less than 0.050 deg./h, and the average bias variation under conventional random vibration test is less than 0.10 deg./h.
文摘An environmentally stable, repetition rate tunable, all-polarization-maintaining, Er-doped pulse fiber laser with a single-wall carbon nanotubes saturated absorber is demonstrated. The ring laser cavity includes a delay line enabling a tunable repetition rate to vary from 35.52 MHz to 35.64 MHz with continuous mode-locked operation. The laser output parameters confirm that the tunable mode-locked operations are stable. High environmental stability is also confirmed by the -130 dBc/Hz low phase noise, a 70-dB signal-to-noise ratio of radio frequency signals, a low amplitude fluctuation of 5.76 × 10-4, and a low fluctuation of reoetition rate of 12 Hz. The laser shows a high de^ree of oolarization of 93%.
基金Project supported by the Initiative Research Program of State Key Laboratory of Precision Measurement Technology and Instruments,Chinathe National Natural Science Foundation of China(Grant No.51527901)
文摘A low-repetition-rate, all-polarization-maintaining（PM）-fiber sub-nanosecond oscillator is presented, which is simple and low-cost, composed of standard components. The ring cavity is elongated by 114-m-long standard PM fiber, and passively mode-locked by a fiber pigtailed semiconductor saturable absorber. Linearly polarized pulses with 1.66 MHz repetition rate and 22 dB polarization extinction ratio are generated at a wavelength of 1030 nm, which is determined by an intracavity filter. In addition, to demonstrate that the oscillator is a good seed for high energy pulse generation, an all-fiber master oscillator power amplifier is built and amplified pulses with energy about 2 μJ are obtained.
文摘A novel type of sampled fiber Bragg gratings （FBGs） written in polarization-maintaining fiber （PMF） is proposed. The reflection spectrum, time delay, and group velocity dispersion （GVD） of the gratings are analyzed. In addition, the reflection spectrum is optimized by apodization. The scheme of multi-wavelength output based on the gratings is proposed, which could be used as a multi-wavelength polarization filter in the density wavelength division multiplexed （DWDM） system.
基金supported by the National Natural Science Foundation of China under Grant No.62005040the Fundamental Research Funds for the Central Universities under Grant No.ZYGX2020KYQD003the Science and Technology Project of Sichuan Province under Grant No.2021YJ0368.
文摘We demonstrated the~2.8-μm and~3.5-μm linearly polarized continuous wave(CW)laser outputs from a polarization-maintaining(PM)Er^(3+)-doped fluoride fiber laser.By introducing a film polarizer into the cavity to select the laser polarization orientation,the~2.8-μm linearly polarized CW laser with a high polarization extinction ratio(PER)of~23 dB and maximum output power of 2.37 W was achieved under double-end pumping at 976 nm.By adding another 1981-nm pump source simultaneously,the~3.5-μm linearly polarized CW laser was also obtained,giving higher PER of~27 dB and maximum output power of 307 mW which is only limited by the available power of 1981-nm pump.To the best of our knowledge,this is the first report on a mid-infrared linearly polarized CW PM fiber laser in the>2.5-μm mid-infrared region.This work not only opens up opportunities for some new mid-infrared applications,but also provides a promising platform for developing high-stability and versatile mid-infrared laser sources.
基金Project supported by the National Natural Science Foundation of China(Grant No.51905528)the Key Research Project of Bureau of Frontier Sciences and Education+1 种基金Chinese Academy of Sciences(Grant No.QYZDY-SSW-JSC008)the National Key Research and Development Project,China(Grant Nos.2019YFB2005600 and 2018YFB2003403)。
文摘We report on a novel architecture to suppress the multi-pulse formation in an all-polarization-maintaining figure-9 erbium-doped fiber laser under high pump power. A 2×2 fiber coupler is introduced into the phase-biased nonlinear amplifying loop mirror to extract part of intracavity laser power as a laser output, and the dependence of output couple ratio of fiber coupler on the mode-locking state is experimentally investigated. The intracavity nonlinear effect is mitigated by lowering the intracavity laser power, which is conducive to avoiding the multi-pulse formation. In the meantime, the loss-imbalance induced by fiber coupler is helpful in improving the self-starting ability. With the proposed laser structure,the multiple pulse formation can be suppressed and high power single pulse train can be obtained. The laser emits three pulse trains which is convenient for some applications. Finally, the output power values of three ports are 5.3 m W, 51.3 m W,and 13.2 m W, respectively. The total single pulse output power is 69.8 m W, which is more than 10 times the result without OC2. The total slope efficiency is about 10.1%. The repetition rate of three pulse trains is 21.17 MHz, and the pulse widths are 2.8 ps, 2.63 ps, and 6.66 ps, respectively.
基金supported by the Program for Changjiang Scholars and Innovative Research Team in University,China(Grant No.PCSIRT:1212)the Key Grant Science and Technology Planning Project of Beijing,China(Grant Nos.PXM2013 014224 000077 and PXM2012 014224 000019)the Science and Technology Planning Project of Beijing Municipal Commission of Education,China(Grant No.KM201611232008)
文摘We present the generation of wavelength-switchable single-polarization solitons in an all-polarization-maintaining erbium-doped fiber laser mode-locked by a graphene saturable absorber. Ultrashort pulses centered at the wavelength of 1531.6 nm with the duration of 816 fs and centered at the wavelength of 1557.8 nm with the duration of 402 fs are separately obtained from the same fiber laser cavity. The cavity loss adjusted by the gold reflector plays a crucial role in wavelength switching.
文摘Long-period fiber gratings have the advantages of small size,corrosion resistance,anti-electro-magnetic interference,and high sensitivity,making them widely used in biomedicine,the power industry,and aerospace.This paper develops a long-period fiber grating sensor based on periodic microchannels.First,a series of linear structures were etched in the cladding of a single-mode fiber by femtosecond laser microma-chining.Then,the laser-modified region was selectively eroded by selective chemical etching to obtain the periodic microchannel structure.Finally,the channels were filled with polydimethylsiloxane(PDMS)to im-prove the spectral quality.The experimental results show that the sensor has good sensitivity in the measure-ment of various parameters such as temperature,stress,refractive index(RI),and bending.It has a temperat-ure sensitivity of−55.19 pm/℃,a strain sensitivity of−3.19 pm/με,a maximum refractive index sensitivity of 540.28 nm/RIU,and a bending sensitivity of 2.65 dB/m^(-1).All of the measurement parameters show good lin-ear responses.The sensor has strong application prospects in the field of precision measurement and sensing.
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 by the National Natural Science Foundation of China(No.61575018)
文摘The heavily germanium(Ge)-doped silica fiber assisted by two air holes in the cladding exhibits high nonlinearity and birefringence,low loss and normal group velocity dispersion(GVD)for two fundamental modes(FMs).When the 1920 nm and 0.1 ps pump pulse with 100 kW peak power is coupled into the 0.5-m-long fiber and polarized along one of two principle axes,the generated spectra can cover the wavelength range around 1000—2500 nm at-20 dB.Furthermore,the output pulse has an excellent coherence in the whole wavelength range.
文摘This paper examines the design and optimization of optical fibers for high-speed data transmission, emphasizing advancements that maximize efficiency in modern communication networks. Optical fibers, core components of global communication infrastructure, are capable of transmitting data over long distances with minimal loss through principles like total internal reflection. This study explores single-mode and multi-mode fiber designs, providing an overview of key parameters such as core diameter, refractive index profile, and numerical aperture. Mathematical modeling using Maxwell’s equations plays a central role in optimizing fiber performance, helping engineers mitigate challenges like attenuation and dispersion. The paper also discusses advanced techniques, including dense wavelength division multiplexing (DWDM), which enables terabit-per-second data rates. Case studies in practical applications, such as fiber-to-the-home (FTTH) networks and transoceanic cables, highlight the impact of optimized designs on network performance. Looking forward, innovations in photonic crystal fibers and hollow-core fibers are expected to drive further improvements, enabling ultra-high-speed data transmission. The paper concludes by underscoring the significance of continuous research and development to address challenges in optical fiber technology and support the increasing demands of global communication systems.
文摘Road construction in Africa is faced with a shortage of quality materials, leading to delays and increased costs. Traditional materials, such as clay soils of the bar soil type, have inadequate properties for pavement sub-base layers, particularly in terms of bearing capacity. This study explores a composite material combining bar soil and bamboo fibers to improve the mechanical performance of bar soil, offering a sustainable and cost-effective solution. The Tori-Bossito bar soil was characterised by particle size analysis, Atterberg limits, Proctor compaction tests and the California Bearing Ratio (CBR). The results show that this material is a class A2 sandy-clay soil with a CBR of 18, which is insufficient for foundation layers requiring a CBR of over 30. To improve its performance, Sèmè-Kpodji bamboo fibers, 30 to 100 microns in diameter and 3 to 5 cm long, were incorporated at rates of 0.9% to 2.7%. The optimum mix, with 2.4% fiber, has a CBR of 35, a dry density of 1.92 t/m3 and a moisture content of 12.4%. This reinforced material is suitable as a base course for low-traffic roadways.
文摘Concrete buildings used in cold regions are prone to freeze-thaw damage, leading to internal cracking and surface peeling of the concrete. Therefore, improving the freeze-thaw resistance of concrete is of great significance for the safety of hydraulic engineering. This paper explores the effect of basalt fibers on improving the frost resistance index of concrete through a series of experiments, and analyzes the influencing mechanism. The results show that adding an appropriate amount of basalt fibers can significantly improve the frost resistance of concrete and reduce the freeze-thaw damage phenomenon indicated by concrete specimens. Adding 0.1% basalt fiber can maintain the relative dynamic modulus of concrete specimens at 98% after 150 freeze-thaw cycles, while adding 0.3% basalt fiber can control the quality loss rate of concrete specimens after 150 freeze-thaw cycles at 0.87%. Taking into account both the frost resistance effect and economic factors, it is recommended that the basalt fiber content in frost resistant concrete be 0.1%. The research results can provide reference and guidance for the optimization design of the mix proportion of hydraulic concrete in cold regions.
文摘Jute is the golden fiber crop of Bangladesh. Viral and Nemic diseases are the major threats to fiber crops, and the fiber yield decreases drastically as the disease infection increases. An experiment was conducted to screen and evaluate ten Jute and allied fiber varieties i.e. BJRI Kenaf-4, BJRI Kenaf-3, HS-95 (Kenaf), HS-24 (Mesta pat), HC-2 (Kenaf), BJRI Deshi pat-8, BJRI Deshi pat-7, BJRI Deshi pat-5, BJRI Deshi pat-6 and CVL-1 against mosaic virus and root-knot nematode disease. It was done in RCBD design with three replications at Sher-e-Bangla Agricultural University (SAU) central farm, Dhaka-1207, from June 2018 to March 2019. In the case of viral infection, variety 4 (HS-24 (Mesta pat)) showed maximum virus incidence (23.11%), whereas variety 2 (BJRI Kenaf-3) had no virus evidence. The most susceptible nematode-infected variety was found in varieties 5 (HC-2 (Kenaf)) and 9 (BJRI Deshi pat-6), which showed 80% incidence, whereas variety 2 (BJRI Kenaf-3) was highly resistance. The growth and yield results showed a significant (0.05%) reduction of plant height (cm) and fiber weight (t/ha) with an increase in the percentage of virus and nematode incidence against all varieties. The highest fiber weight (1.47 t/ha) and the lowest viral (0%) and nemic infection (0%) were found in variety 2 (BJRI Kenaf-3), which showed better performance compared to other varieties. These results revealed that variety 2 (BJRI Kenaf-3) had the best variety in the present study.
文摘Bangladesh’s thriving okra cultivation sector annually yields substantial harvests, yet a significant portion of the plant remains underutilized after harvesting, posing as agricultural waste. This oversight neglects the economic potential of okra fiber, which is versatile and valuable across various industries. This paper explores this untapped potential by investigating the physico-mechanical properties, chemical treatments, and fabrication techniques of okra fiber, drawing from a wealth of research. Comparative analyses with established natural fibers like jute and sisal shed light on okra fiber’s transformative role in Bangladesh’s economic landscape. Along with the applications in the fashion world, meticulous investigation into its mechanical, thermal, and morphological characteristics uncovers inherent strengths and integration pathways into industrial applications. Strategies for optimizing yield and quality, including novel approaches like photo-grafting and protein extraction, are explored. Considerations for cytotoxicity and environmental sustainability ensure its viability as a green resource. This research aims to unlock okra fiber’s full potential, positioning Bangladesh for sustainable economic development and innovation.
