Abstract: A double-deck rail vehicle and a vehicle body thereof are provided. An underframe (11) of the vehicle body comprises a lower-layer underframe (111), end underframes (112, 115), sealing plates (114, 116), and side underframes (118, 119); wherein the lower-layer underframe is provided with an underframe middle beam (1111); the end underframe is fixedly connected to the underframe middle beam by means of reinforcement middle beams (113, 117); the sealing plate is fixedly connected between the end underframe and the lower-layer underframe; and the side underframe comprises side beams (1181, 1191) of the side underframe that are integrated, and the side underframe is fixedly connected to the end underframe by means of the side beams of the side underframe. The vehicle body supplements the reinforcement middle beams capable of increasing the connection strength between the end underframe and the lower-layer underframe, and uses the integrated side beams of the side underframe.

Abstract: The present invention discloses a transverse mode switchable all-fiber high-order mode Brillouin laser. The laser comprises a narrow linewidth pump laser, an optical amplifier, a 1×N optical switch (N?2), a fiber mode selection coupler group, a first polarization controller, a fiber circulator, a fiber coupler, a second polarization controller, and a few-mode fiber. Based on the Brillouin nonlinear gain of a few-mode fiber in a ring cavity, the present invention realizes the resonance amplification of a specific order transverse mode in the cavity, and obtains the transverse mode switchable high-order mode laser beam output. The present invention, adopting an all-fiber structure, has the advantages of simple structure, low cost, easy fiber system integration, high stability and narrow linewidth of outputted laser beams, etc., and improves the practicality and reliability of high-order mode lasers.

Abstract: Disclosed is an all-fiber optical vortex laser based on resonance of orbital angular momentum modes. The all-fiber optical vortex laser has an annular cavity structure, and includes a narrow-linewidth pump laser, an optical amplifier, an orbital angular momentum mode generator, a first polarization controller, an optical fiber circulator, an optical fiber coupler, a second polarization controller and a vortex optical fiber. The orbital angular momentum mode generator (3) realizes directional conversion from a fundamental transverse mode in a single-mode optical fiber into an orbital angular momentum mode with a specific topological charge in a vortex optical fiber. The optical fiber coupler can realize directional coupling from an orbital angular momentum mode in one vortex optical fiber to an orbital angular momentum mode in another vortex optical fiber; the vortex optical fiber is an optical fiber supporting stable transmission of an orbital angular momentum model.

Abstract: The present invention discloses a transverse mode switchable all-fiber high-order mode Brillouin laser. The laser comprises a narrow linewidth pump laser, an optical amplifier, a 1×N optical switch (N?2), a fiber mode selection coupler group, a first polarization controller, a fiber circulator, a fiber coupler, a second polarization controller, and a few-mode fiber. Based on the Brillouin nonlinear gain of a few-mode fiber in a ring cavity, the present invention realizes the resonance amplification of a specific order transverse mode in the cavity, and obtains the transverse mode switchable high-order mode laser beam output. The present invention, adopting an all-fiber structure, has the advantages of simple structure, low cost, easy fiber system integration, high stability and narrow linewidth of outputted laser beams, etc., and improves the practicality and reliability of high-order mode lasers.

Abstract: A manufacturing technique of ultra-wideband high gain optical fibers and devices is disclosed, including: (1) manufacturing a gain fiber, which is a composite structural optical fiber, having a core composed of a plurality of sets of sector structures distributed symmetrically or a plurality of concentric ring structures. The core is composed of at least two kinds of rare-earth-ion-doped glass, and luminescence centers are located in different sector or ring structure regions; and (2) constructing a fiber laser: using the gain fiber, selectively exciting rare earth ions in different regions in the core by controlling a shape of pump light spot, and combining with fiber grating pairs to realize a tunable laser output. The present disclosure can manufacture gain fibers with high-gain and ultra-wideband characteristics by combining the design of the fiber structure and the control of the light field of the pump light.