Showing papers by "Liang Chen published in 2023"
TL;DR: In this article , a strain-insensitive BGS linewidth was achieved by selecting the fiber gain section under the combined effects of the longitudinal acoustic velocity VA, strain dependence of refractive indexn, the effective fiber lengthLeff and also the pump intensityI along the non-uniform As2Se3-PMMA tapered fiber.
Abstract: Stimulated Brillouin scattering and the longitudinal strain performance based on Brillouin Optical Time Domain Analysis (BOTDA) in a 50 cm long nonuniform As2Se3-PMMA tapered fiber is theoretically and experimentally investigated. In the BOTDA measurement a 20 ns pump pulse is used, of which the pulse-width equivalent length is longer than the fiber under test (FUT) of 50 cm nonuniform As2Se3-PMMA tapered fiber. The evolution of Brillouin gain spectrum (BGS) corresponding to different fiber sections is analyzed showing the strain performance of the shift of the BGS frequency and the change of BGS linewidth under the imposed longitudinal strain. A strain-insensitive BGS linewidth is achieved by selecting the fiber gain section under the combined effects of the longitudinal acoustic velocity VA, strain dependence of refractive indexn, the effective fiber lengthLeff and also the pump intensityI along the nonuniform As2Se3-PMMA tapered fiber. The proposed method has the potential for many novel applications such as strain-insensitive sensing device, multiple-parameter sensors and the distributed sensing measurement along the nonuniform As2Se3-PMMA tapered fibers.
DOI•
TL;DR: In this article , the authors investigated the performance of PMMA tapered fiber with a 20 ns pump pulse and showed the strain performance of the shift of the BGS frequency and the change of BGS linewidth under the imposed longitudinal strain.
Abstract: Stimulated Brillouin scattering and the longitudinal strain performance based on Brillouin Optical Time Domain Analysis (BOTDA) in a 50 cm long nonuniform As$_{2}$ $_{3}$ $_{2}$ $_{3}$ $V_{A}$ $n$ $L_{eff}$ $I$ $_{2}$ $_{3}$ $_{2}$ $_{3}$
TL;DR: In this paper , the role of foreign direct investment (FDI) in the internationalization of digital companies is investigated. And the authors show that FDI is more likely to occur if the foreign market is far away or culturally very different from the company's home country, and the strength of this relationship differs among B2C and B2B business models.
Abstract: Research Summary Recent global strategy research on born digital firms (i.e., firms with digital products distributed through digital channels) has paid only limited attention to the role of foreign direct investment (FDI) in the internationalization of such firms. We argue that exploiting digital technologies requires a range of complementary, non-digital resources. Born digitals typically deploy FDI when large cultural and geographic distances limit the fungibility and scalability of such complementary resources, leading to a positive relationship between distance (cultural and geographic) and FDI. The positive distance effect is moderated by business model type. Using a sample of US-based born digital firms with over 800 FDIs, we find support for our hypotheses and contribute an important empirical baseline to recent discussions of digitalization in global strategy. Managerial Summary Companies selling digital products (e.g., software, cloud-based services) are theoretically able to offer their products in foreign markets through internet-based channels, without ever setting foot in a foreign country. And yet, many “born digital” firms establish a physical presence in foreign markets by undertaking foreign direct investment (FDI). This phenomenon remains insufficiently explained. We argue that FDI can supply important complementary resources that help exploit and monetize digital assets in foreign markets. Using data from over 800 FDI projects, we show that FDI is more likely to occur if the foreign market is far away or culturally very different from the company's home country, and that the strength of this relationship differs among B2C and B2B business models.
TL;DR: Based on the related environmental data of Chengdu and Chongqing from 2011 to 2020, the authors constructs a multivariate environment performance evaluation system, combines the self-built indicator system determination criteria and rules, evaluates and compares the environmental performance, and also discusses the impact of COVID-19 on urban environmental performance.
Abstract: Based on the related environmental data of Chengdu and Chongqing from 2011 to 2020, this paper constructs a multivariate environment performance evaluation system, combines the self-built indicator system determination criteria and rules, evaluates and compares the environmental performance of Chengdu and Chongqing, and also discusses the impact of COVID-19 on urban environmental performance. The research results show that the overall environmental performance increased from 2011 to 2020, but there are differences between different subsystems, mainly manifested in the best water environment performance, followed by air environment and solid waste; moreover, the noise environment maintains a relatively stable level. By comparing the average levels of various subsystems of the Chengdu-Chongqing dual cities from 2011 to 2020, it can be seen that Chengdu City has better environmental performance in air environment and solid waste, while Chongqing City has better environmental performance in the water environment and noise environment. In addition, this paper also found that the impact of the epidemic on urban environmental performance mainly comes from the impact on the air environment. At present, the overall environmental performance of the two places has shown a trend of environmentally coordinated development. In the future, Chengdu and Chongqing should further optimize and improve their relatively weak environmental subsystems, deepen the joint action mechanism between the two places, and build a green and high-quality development economic circle for the Chengdu-Chongqing twin cities.
TL;DR: In this paper , a multi-wavelength Brillouin random fiber laser with the channel space of triple frequency shift and high polarization orthogonality between adjacent wavelengths (TOP-MWBRFL) is proposed.
Abstract: A novel multi-wavelength Brillouin random fiber laser with the channel space of triple Brillouin frequency shift and high polarization orthogonality between adjacent wavelengths (TOP-MWBRFL), to the best of our knowledge, is experimentally demonstrated. The TOP-MWBRFL is structured in a ring form by cascading two Brillouin random cavities of single-mode fiber (SMF) and one Brillouin random cavity of polarization-maintaining fiber (PMF). Based on polarization pulling properties of stimulated Brillouin scattering in long-distance SMFs and PMFs, the states of polarization (SOPs) of lasing light from SMF random cavities are linearly bounded to the SOPs of local pump light, whereas the SOP of lasing light from the PMF random cavity is strictly clamped on one of the principal axes of the PMF. Thus, the TOP-MWBRFL can stably emit multi-wavelength light with high polarization extinction ratio (>35d B) between adjacent wavelengths without precise polarization feedback. In addition, the TOP-MWBRFL can also work in one polarization mode to stably lase multi-wavelength light with SOP uniformity as high as 37 dB.
TL;DR: In this article , a photon-echo-like phenomenon induced by a phonon was demonstrated, whose mechanism is represented by a coherent photon-phonon chain interaction (PPCI) theory referring to the alternating evolution between Stokes scattering and anti-Stokes scattering.
Abstract: Photon-phonon interaction is a powerful mechanism for all-optical signal processing, slow (fast) light, microscopy, spectroscopy, microwave photonics, and sensing. Here, we demonstrate a photon-echo-like phenomenon induced by a phonon, whose mechanism is represented by a coherent photon-phonon chain interaction (PPCI) theory referring to the alternating evolution between Stokes scattering and anti-Stokes scattering. An analytical solution, including the impulse response of the coherent PPCI theory, is derived to quantitatively analyze the energy conversion between photon and phonon, showing a damped photoacoustic oscillation. All theoretical analysis, numerical simulation, and experiments confirm that the adjacent order echoes have a phase difference of \ensuremath{\pi}, i.e., phase flip, and the echoes generated by using photon and phonon as the initial excitation sources, respectively, are in inverse phase. As a result, the echoes up to the third-order are theoretically analyzed by the proposed coherent PPCI theory and verified by the experiment. This physical mechanism bodes well for a class of photonics applications in telecommunications, optical metrology, and optical computation.
TL;DR: Wang et al. as mentioned in this paper created a comprehensive evaluation index system of low-carbon city multivariate system based on carbon emission data from 30 typical Chinese cities from 2006 to 2017 and evaluates and analyzes the trend of city low carbon levels using the CRITIC-TOPSIS technique and MK method.
Abstract: Abstract Low-carbon city construction is one of the key issues that must be addressed for China to achieve high-quality economic development and meet the Sustainable Development Goals. This study creates a comprehensive evaluation index system of low-carbon city multivariate system based on carbon emission data from 30 typical Chinese cities from 2006 to 2017 and evaluates and analyzes the trend of city low-carbon levels using the CRITIC-TOPSIS technique and MK method. Meanwhile, the influence mechanism of the multi-coupled system is investigated using the coupling coordination degree model and random forest algorithm.The results show that there are 8 cities with a significant increasing trend of low-carbon level, 19 cities with no significant monotonic change trend, and 3 cities with a decreasing trend of low-carbon level. By analyzing the coupling coordination degree, we found that the coupling coordination degree between low-carbon level and economic development in most cities tends to increase year by year, from the initial antagonistic effect to a good coordination development trend, which confirms the “inverted U-shaped” relationship between economy and carbon emission. In addition, industrial pollutant emissions, foreign direct investment, and economic output are the core drivers of low-carbon levels in cities.
01 Oct 2023
TL;DR: In this article , the authors demonstrate a self-injection locking (SIL) in an Er-doped random fiber laser by a high quality factor (high-Q) random fiber grating ring (RFGR) resonator, which enables a single-mode narrow-linewidth lasing with ultra-low intensity and frequency noise.
Abstract: We demonstrate a self-injection locking (SIL) in an Er-doped random fiber laser by a high quality factor (high-Q) random fiber grating ring (RFGR) resonator, which enables a single-mode narrow-linewidth lasing with ultra-low intensity and frequency noise. The RFGR resonator includes a fiber ring with a random fiber grating to provide random feedback modes and noise suppression filters with self-adjusted peak frequency adaptable to small perturbations allowing single longitudinal mode over 7000 s with frequency jitter below 3.0 kHz. Single-mode operation is accomplished by carefully controlling phase delays and mode coupling of resonant modes between main ring and RFGR with a side-mode suppression ratio of 70 dB and narrow linewidth of 1.23 kHz. The relative intensity noise is -140 dB/Hz above 100 kHz and the frequency noise is 1 Hz/Hz1/2 above 10 kHz.