Twin-tube terahertz fiber for a polarization filter.

A simple polymer twin-tube terahertz (THz) fiber that can be used as a polarization filter is proposed and investigated using the finite element method in this paper. The twin-tube THz fiber consists of two closely spaced identical tubes located symmetrically inside the protecting jacket. The simulation results show that the y-polarization fundamental mode (YPFM) can be well confined between the two tube walls near the fiber center, while the x-polarization fundamental mode (XPFM) has a huge confinement loss due to the coupling with the tube mode.

Low bending loss few-mode hollow-core anti-resonant fiber with glass-sheet conjoined nested tubes.

A novel hollow-core anti-resonant fiber (HC-ARF) with glass-sheet conjoined nested tubes that supports five core modes of LP01-LP31 with low mode couplings, large differential group delays (DGDs), and low bending losses (BLs) is proposed. A novel cladding structure with glass-sheet conjoined nested tubes (CNT) is induced for the proposed HC-ARF which can suppress mode couplings between the LP01-LP31 modes and the cladding modes. The higher-order modes (HOMs) which are LP11-LP31 modes also have very low loss by optimizing the radius of the nested tube and the core radius.

Deformation Monitoring of Metro Tunnel with a New Ultrasonic-Based System.

With the rapid construction of metro tunnels in many metropolises, a fast and convenient solution to capture tunnel deformation is desired by civil engineers. This contribution reports an automatic and wireless tunnel deformation monitoring system using ultrasonic transducers. A processing algorithm of the redundant ultrasonic information (RUI) approach is proposed to improve measurement accuracy.