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Optimal output coupler grating reflectivity for Er/Yb fiber lasers
摘要： We measure the output power of an Er/Yb fiber laser with twelve different SMF-28 narrowband output couplers and demonstrate experimentally that the optimal reflectivity is ~1%. The fiber laser efficiency with the optimal output coupler is ~38% at ~1546 nm. In addition, we successfully inscribe a similar output coupler in situ during laser operation with 800 nm femtosecond pulses and the phase mask technique. An output power very close to the optimal was obtained with the in situ inscribed output coupler. With a flat cleaved broadband output coupler, the efficiency is ~42%, which is the highest reported efficiency of an Er/Yb fully integrated fiber laser.
关键词： Fiber lasers,Fiber Bragg gratings,Ultrafast optics
更新于2025-09-16 10:30:52
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[IEEE 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Huangshan, China (2019.8.5-2019.8.8)] 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Multi-points ultrasound detection with multiple FBGs and a pseudo-synchronous method
摘要： A novel pseudo-synchronous method(PSM)is proposed to realize the multi-points detection of ultrasound with fiber Bragg sensors (FBGs) connected in serials, to overcome the problems encountered by employing conventional wavelength demodulator for FBGs at relatively low repeat frequency(~1kHz), comparing with the much higher frequency up to several tens of kHz of the ultrasound to be detected. The novel detection scheme has been demonstrated effectively when the ultrasound was excited and propagating on the surfaces of an aluminium plate and a section of stainless steel tube, respectively. The experimental measurement shows the in practical detection method has good prospect application such as the non-destructive test (NDT), etc.
关键词： pseudo-synchronous method,ultrasound detection,fiber Bragg gratings
更新于2025-09-16 10:30:52
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Optical Fiber Tag Based on an Encoded Fiber Bragg Grating Fabricated by Femtosecond Laser
摘要： A type of encoded FBG array for use as an optical fiber tag is inscribed using a femtosecond laser line-by-line technique. Each tag included two labels and several codes formed by grating fragments with a predetermined length. Encoded information was characterized by measuring the backscattered optical signal. Local spectra from the internal grating fragments were then used to enlarge the encoding capacity or encrypt the encoded FBG. The insertion loss of the device is as low as < 0.1 dB.
关键词： Fiber Bragg gratings,Backscattering,Fiber optics components
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Tunable All-Fiber Laser for Remote Sensing of Methane Near 3.4 μm
摘要： The mid-infrared (MIR) region of the optical spectrum has drawn considerable scientific interest in the past few years. Indeed, several molecules relevant to medical or environmental conundrums exhibit strong absorption lines in this region: for instance, methane lines in the MIR are up to 100 times stronger than in the near-infrared [1]. In turn, fiber lasers have long stood as prime candidates for remote gas detection in outdoor environments, given their exemplary robustness, power scaling and beam quality. However, while several previous contributions have targeted methane bands under 3.3 μm in wavelength [2], little work has been done to push fiber laser detection tools past 3.4 μm, where methane absorption lines are mostly decoupled from the absorption spectra of water and other atmospheric constituents. This is especially relevant when probing CH4 through a gas mixture with relatively high water content, such as when studying gas emission from methane-rich thermokarst lakes in northern regions. To this end, we present a tunable all-fiber laser emitting near 3.43 μm and operating at high average power. The laser design (Fig. 1) is based on an all-fiber dual-pumping scheme [3], which combines core-pumping at 1976 nm with clad-pumping at 976 nm in a single-mode erbium-doped fluoride glass fiber to reach, in the present case, up to 3 W of output power at the desired wavelength. The laser cavity itself is delimited by two fiber Bragg gratings (FBG): a highly-reflective (HR) FBG at the input, which has a narrow bandwidth to dictate the laser wavelength, and a lowly-reflective (LR) FBG at the output, which has a large bandwidth to accommodate shifts of the HR FBG. Tuning of the laser cavity is achieved by mechanically stretching (i.e. lengthening) the HR FBG via the beam bending technique [4]. The HR FBG is nested within an Invar-based metallic groove and fixed using a polymer of sufficient elasticity, the groove is then deformed using a piezoelectric actuator (PA), allowing for rapid and precise wavelength tuning over a wavelength range of a few nanometers. Figure 2 compares normalized spectra of the laser emission at various commanding voltages for the PA along with the absorption spectrum of methane as given by the HITRAN database [1]. As can be seen on Fig.2, the presence of consecutive extrema (min-max) allows for quick referencing of the measurement during each tuning cycle. Early gas cell experiments and further engineering refinement show good promise for future deployment in northern regions by climate scientists.
关键词： methane,remote sensing,mid-infrared,piezoelectric actuator,fiber Bragg gratings,tunable all-fiber laser
更新于2025-09-12 10:27:22
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An integrated biological analysis and flow rate sensing for the real-time detection of carcinogen in water based on Co2+-doped optical fibers
摘要： The multi-parameter measurement has significant meaning for biosensor to enhance their practical sensing performance. For the biological detection, simultaneous measurement of biological molecule and flow rate could improve the accuracy and sensitivity of sensors significantly. In this paper, an integrated biological analysis and flow rate sensing based on Co2+ doped tilted fiber Bragg gratings has been proposed and experimentally demonstrated for the detection of the Benzo[a]pyrene molecules. A tilted fiber Bragg grating with a tilted angle of 8o was inscribed into a Co2+ doped fiber. The flow rate and Benzo[a]pyrene molecules can be measured simultaneously by interrogating the resonance wavelength of core mode and wavelength interval between the core mode and cladding mode according to the heat exchange and evanescent field of the cladding mode, respectively. Experimental results show that the real-time measurement sensitivities of 12 pm/pM and -0.13 nm/(μL/s) for the Benzo[a]pyrene detection and flow rate were achieved, respectively. Thus the technique appears to have potential applications in chemistry, medicine, and biology.
关键词： Thermal effects,Co2+ doped tilted fiber Bragg gratings,Flow rate measurement,Benzo[a]pyrene detection
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Numerical and Experimental Study on the IR Femtosecond Laser and Phase Mask-Based Grating Inscription in Photonic Crystal Fibers
摘要： Femtosecond pulse laser sources enable the fabrication of fiber Bragg gratings (FBGs) in non-photosensitive fibers, allow for through coating grating inscription when working at infrared (IR) wavelengths and can provide for high temperature stable gratings. Target applications for such gratings include, but are not limited to, optical communications, fiber lasers and fiber sensing. When dealing with such grating inscription method in photonic crystal fibers (PCF) however, the presence of air holes in the fiber cladding impedes the delivery of the femtosecond laser pulse energy to the fiber core, which in its turn significantly affects the index change through non-linear absorption processes in the fiber core [1]. Our research focuses on this issue in view of understanding how the grating writing laser pulses interact with the PCF’s holey structure and of enabling more efficient femtosecond laser-based inscription of FBGs in PCFs. Here we report on the inscription of FBGs in a hexagonal lattice PCF using a femtosecond pulse laser operating at 1030 nm with a phase mask and a short focal length cylindrical lens (f=10 mm) that focuses light to the fiber core [2]. We first looked into the influence of the alignment on laser beam focusing in the cross-section of the PCF by comparing the focusing characteristics to those in standard step-index single mode fiber. As a figure of merit, we used the transverse coupling efficiency (TCE), which is defined as the ratio of the integrated core field intensities simulated (using Lumerical FDTD Solutions?) in the presence and absence of holey cladding. Fig. 1b shows how the TCE changes as the fiber is translated along the X and Y axes in the cross-sectional plane. X=0 and Y=0 corresponds to focused to the center of the core, and negative Y indicates translation of the fiber away from the lens (see Fig. 1a). For a step-index fiber we observe a typically elongated region in which we find optimal coupling with TCE=1 (no air holes) for a beam waist of 2.34 μm and a depth of focus of 15.7 μm. Fig. 1c shows an alignment map for a hexagonal lattice PCF (with structure shown in the inset of Fig. 1d), when light is incident along the ΓK axis of the hexagon. We can identify three distinct regions with a TCE around 0.6. Those appear when the fiber is shifted by around 15 μm and 30 μm further from the lens. This offset indicates that optimal coupling of the grating writing beam to the PCF core requires focusing to the edge of the holey cladding or closer to the silica cladding region of the fiber, rather than to the core center. Fig. 1 a) Fiber translational axes and translation dependence of the transverse coupling efficiency (TCE) for b) step-index fiber and c) PCF. d) Spectra of the IR femtosecond pulse inscribed FBG in the PCF (SEM image in the inset). We then inscribed FBGs in the above mentioned hexagonal lattice PCF with a commercial Yb:KGW ultrafast regenerative amplifier system Pharos 6W (Light Conversion) at 1030 nm and 190 fs duration pulses at a repetition rate of 100 Hz. We used high accuracy alignment stages to find the best coupling position by monitoring the luminescence (around 420 nm) from the Ge-doped core. The reflection and transmission spectra of the inscribed FBG are shown in Fig. 1c. We achieved an almost 4 dB strong FBG in around 4 seconds using a laser power of 450 mW. To the best of our knowledge it is the first time that the difference between regular step-index fibers and PCFs in best focusing conditions for IR femtosecond laser-based FBG writing is studied and that such a FBG is realized in a PCF using a 1030 nm source and a phase mask technique with a short focal length cylindrical lens.
关键词： phase mask,photonic crystal fibers,Femtosecond pulse laser,fiber Bragg gratings,transverse coupling efficiency
更新于2025-09-12 10:27:22
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Fiber Laser || Active Q-switched Fiber Lasers with Single and Dualwavelength Operation
摘要： A brief explanation on Q-switched fiber laser operating principle for active technique in terms of operation characteristics is presented. Experimental analysis of proposed pulsed fiber lasers by the active Q-switched technique is demonstrated. Experimental setups include the use of Er/Yb doped fiber as a gain medium and an acousto-optic modulator as cavity elements. Setup variations include the use of fiber Bragg gratings for wavelength selection and tuning and Sagnac interferometer for wavelength selection in single wavelength operation and for cavity loss adjustment in dual wavelength operation. The experimental analysis of principal characteristics of single-wavelength operation of the fiber laser and cavity loss adjustment method for dual-wavelength laser operation are discussed.
关键词： fiber Bragg gratings,Sagnac interferometer,Er/Yb double-clad fibers,Q-switched lasers
更新于2025-09-11 14:15:04
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[IEEE 2018 Asia Communications and Photonics Conference (ACP) - Hangzhou (2018.10.26-2018.10.29)] 2018 Asia Communications and Photonics Conference (ACP) - All-Fiber Passively Mode-Locked Erbium-Doped Fiber Laser Using a Femtosecond Laser Inscribed 45°-Tilted Fiber Grating
摘要： A passively mode-locked fiber laser using femtosecond inscribed plane-by-plane 45°-tilted fiber grating is experimentally demonstrated. The generated solitons center at 1561.8 nm with bandwidth reaching 7.14 nm and pulse width of 1.1 ps.
关键词： fiber Bragg gratings,mode-locked lasers,nonlinear polarization rotation
更新于2025-09-11 14:15:04
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[IEEE 2018 IEEE International Instrumentation and Measurement Technology Conference (I2MTC ) - Houston, TX, USA (2018.5.14-2018.5.17)] 2018 IEEE International Instrumentation and Measurement Technology Conference (I2MTC) - Temperature compensation method for FBG-based current sensors for transmission lines
摘要： A method to compensate the temperature influence on electrical current sensors based on fiber Bragg gratings (FBG) is presented in this paper. The operating principle of the method is the employment of a second fiber Bragg grating in the measurement system, called fixed filter, in order to interrogate the output signal from the sensing grating. Once both gratings have been attached to Terfenol-D rods close to each other and subjected to the same temperature variations inside a protective cover, the separation of magnetostrictive strain from the one related to temperature in the output signal can be obtained.
关键词： magnetostrictive strain,sensing grating,fiber Bragg gratings,Current sensors,Terfenol-D,fixed filter
更新于2025-09-11 14:15:04
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On crack propagation monitoring by using reflection spectra of AFBG and UFBG sensors
摘要： Due to their light weight, small size and immunity to electromagnetic interference, Fiber Bragg Gratings (FBG) have shown great potential in structural health monitoring (SHM) area. Ordinarily, FBGs are used as the quasi-distributed sensors to detect structural damage by central wavelengths shifting, which has robust problem in real engineering application. It is found that the FBG reflection spectra can also be distorted with the non-uniform strain field caused by crack. Multiple indices can be extracted from the reflection spectra which can provides more information on the crack propagation. However, till now no researches have been investigated regarding the behaviors of different kinds of FBGs for crack propagation monitoring based on the FBG reflection spectra. In this paper, behaviors of the apodized FBG (AFBG) and the uniform FBG (UFBG) sensors for structural crack propagation monitoring are investigated. The reflective spectral behaviors of both UFBG and AFBG sensors under crack-generated non-uniform strain are illustrated by simulation and experiment. Three spectra indices, namely the central wavelength shift, the ratio of side lobe to main lobe and the information entropy, are proposed to indicate the propagation of the crack. The results show the UFBG sensors have better performance than the AFBG sensors which are more suitable for crack propagation monitoring.
关键词： crack propagation monitoring,uniform fiber Bragg gratings,apodized fiber Bragg gratings,structural health monitoring,spectral distortion
更新于2025-09-10 09:29:36