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Satellite-based quantum communication is a promising approach for realizing global-scale quantum networks. For free-space quantum channel, single-mode fiber coupling is particularly important for improving the signal-to-noise ratio of daylight quantum key distribution (QKD) and compatibility with standard fiber-based QKD. However, achieving a highly efficient and stable single-mode coupling efficiency under strong atmospheric turbulence remains experimentally challenging. Here, we develop a single-mode receiver with an adaptive optics (AO) system based on a modal version of the stochastic parallel gradient descent (M-SPGD) algorithm and test its performance over an 8 km urban terrestrial free-space channel. Under strong atmospheric turbulence, the M-SPGD AO system obtains an improvement of about 3.7 dB in the single-mode fiber coupling efficiency and a significant suppression of fluctuation, which can find its applications in free-space long-range quantum communications.
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http://dx.doi.org/10.1364/OE.411939 | DOI Listing |
Sensors (Basel)
August 2025
School of Physics and Technology, University of Jinan, Jinan 250022, China.
A respiratory monitoring sensor based on a balloon-shaped optical fiber is proposed. The sensor consists of a single-mode fiber (SMF) coated with polydimethylsiloxane (PDMS) bent into a balloon shape to form a fiber optic Mach-Zehnder interferometer. The sensor's sensitivity to temperature enables monitoring of breathing status by recognizing the temperature changes that occur during human respiration.
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September 2025
In a conventional Brillouin optical time-domain analysis (BOTDA) system, the inherent two-end access architecture requires a roundtrip wiring layout for the fiber under test (FUT), which fundamentally limits the actual sensing range to half of the total fiber length. In this paper, an end-to-end topology configuration for a BOTDA system is proposed, with long range and open path. The pump light and the probe light are sent into the FUT from the opposite ends, while their generation modules are physically put at the near end and far end, respectively.
View Article and Find Full Text PDFWe demonstrate a submillimeter-length single-helix chiral grating embedded in a high-numerical-aperture single-mode fiber (HNA-SMF) for efficient generation of third-order orbital angular momentum (OAM), specifically the OAM mode. This design facilitates enhanced coupling of higher azimuthal modes due to significant perturbations arising from both the geometric effect of the thin-core offset under high-NA conditions and the elasto-optic effect induced by intense helical stress with a small twist pitch. As a result, we achieve an unprecedented device length of 0.
View Article and Find Full Text PDFSelf-similar evolution has garnered significant attention in the field of high-power ultrafast fiber lasers due to its unique characteristics, such as wave-breaking suppression and quasi-linear chirp properties. Here, we demonstrate the spatiotemporal similariton generation in an all-fiber laser system through dual-function spectral-spatial filtering enabled by a commercial single-mode fiber filter. The system delivers similaritons centered at 1066 nm with M≈2.
View Article and Find Full Text PDFSpatiotemporal mode-locking (STML) in multi-mode fibers provides a novel approach, to our knowledge. to overcoming the power limitations of conventional single-mode lasers. However, the existing spatial filtering-based STML schemes are limited by the number of locked transverse modes, which severely constrains the power enhancement.
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