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In-Fiber Collimator-Based Fabry-Perot Interferometer with Enhanced Vibration Sensitivity
摘要： A simple vibration sensor is proposed and demonstrated based on an optical fiber Fabry-Perot interferometer (FPI) with an in-fiber collimator. The device was fabricated by splicing a quarter-pitch graded index fiber (GIF) with a section of a hollow-core fiber (HCF) interposed between single mode fibers (SMFs). The static displacement sensitivity of the FPI with an in-fiber collimator was 5.17 × 10?4 μm?1, whereas the maximum static displacement sensitivity of the device without collimator was 1.73 × 10?4 μm?1. Moreover, the vibration sensitivity of the FPI with the collimator was 60.22 mV/g at 100 Hz, which was significantly higher than the sensitivity of the FPI without collimator (11.09 mV/g at 100 Hz). The proposed FPI with an in-fiber collimator also exhibited a vibration sensitivity nearly one order of magnitude higher than the device without the collimator at frequencies ranging from 40 to 200 Hz. This low-cost FPI sensor is highly-sensitive, robust and easy to fabricate. It could potentially be used for vibration monitoring in remote and harsh environments.
关键词： fiber vibration sensor,graded index fiber,Fabry-Perot interferometer
更新于2025-11-28 14:23:57
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Prediction of First Higher Order Modal Field for Graded Index Fiber in Presence of Kerr Nonlinearity
摘要： We report evaluation of first higher order modal field for dual mode optical fiber having step and parabolic index profiles. The study is carried out both in absence as well as in presence of Kerr nonlinearity. The analysis is based on a simple iterative method involving Chebyshev formalism. Taking some typical step- and parabolic-index fibers as examples, we show that our results agree excellently with the exact results which can be obtained by applying rigorous methods. Thus, our simple formalism stands the merit of being considered as an accurate alternative to the existing cumbersome methods. The prescribed formalism provides scope for accurate estimation of different propagation parameters associated with first higher order mode in such kinds of fibers in presence of Kerr nonlinearity. The execution of formalism being user friendly, it will be beneficial to the system engineers working in the field of optical technology.
关键词： first higher order modal field,dual mode graded-index fiber,Kerr nonlinearity,Chebyshev technique
更新于2025-09-23 15:23:52
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2nd-order random lasing in a multimode diode-pumped graded-index fiber
摘要： Raman lasing in a graded-index fiber (GIF) attracts now great deal of attention due to the opportunity to convert high-power multimode laser diode radiation into the Stokes wave with beam quality improvement based on the Raman clean-up effect. Here we report on the cascaded Raman generation of the 2nd Stokes order in the 1.1-km long GIF with 100-μm core directly pumped by 915-nm diodes. In the studied all-fiber scheme, the 1st Stokes order is generated at 950–954 nm in a linear cavity formed at GIF ends by two fiber Bragg gratings (FBGs) securing beam quality improvement from M2 ≈ 30 to M2 ≈ 2.3 due to special transverse structure of FBGs. The 2nd Stokes wave is generated either in linear (two FBGs) or half-open (one FBG) cavity with random distributed feedback via Rayleigh backscattering. Their comparison shows that the random lasing provides better beam quality and higher slope efficiency. Nearly diffraction limited beam (M2 ≈ 1.6) with power up to 27 W at maximum gain (996 nm), and 17 W at the detuned wavelength of 978 nm has been obtained, thus demonstrating that the 2nd-order random lasing in diode-pumped GIF with FBGs provides high-efficiency high-quality beam generation in a broad wavelength range within the Raman gain spectral profile.
关键词： laser diode,fiber Bragg gratings,beam quality,graded-index fiber,Raman lasing,random distributed feedback
更新于2025-09-23 15:21:21
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976a??nm all-fiber Raman laser with high beam quality at multimode laser diode pumping
摘要： A 976 nm all-fiber Raman laser enabling high beam quality at direct multimode laser diode pumping with low beam quality (M2 > 30) is demonstrated. The laser is performed in a 100/140 multimode graded-index fiber with special in-fiber Bragg gratings that secure generation of the Stokes beam with relatively good quality (M2 ? 2) and high slope efficiency of the pump-to-Stokes conversion (70%) at output powers of up to ~50 W.
关键词： graded-index fiber,fiber laser,diode pumping,Raman laser
更新于2025-09-23 15:19:57