Displacement Sensing of an Active String Actuator by an Optical Fiber

We have fabricated a string-shaped actuator called “Active string” that has high contractile displacement/force by accumulating thin pneumatic artificial muscles using the string production process. However, displacement control of the active string is challenging because general bulky and rigid displacement sensors are not suitable for the sensor element of the active string. Therefore, in this report, a flexible optical fiber sensor is combined with the active string to enable sensing of its displacement. As the active string contracts, the radius of curvature of the optical fiber decreases, and light intensity propagating in the optical fiber decreases due to bending loss. The experimental results showed that the optical fiber sensor value changed with corresponding to the displacement of the active string. It shows the possibility that it is possible to make a displacement estimation of the displacement of the active string using an optical fiber sensor.

Compact Single-Frequency MOPA Using a Silica Fiber Highly Doped with Yb3+

We report on a single-frequency fiber master oscillator power amplifier utilizing a polarization-maintaining step-index fiber with an Al/Ce/F core-glass composition doped with a very high Yb concentration (0.25 at.%). This design made it possible to use a very short fiber (~1 m) and to coil it in a tight radius (4 cm in the amplifier, while 2 cm gave similarly negligible bending loss) so that the packaged system is one of the most compact reported to date (~0.6 L). The use of a short fiber increased the threshold for stimulated Brillouin scattering well above 100 W while maintaining near-ideal beam quality. The fiber was pumped with a diode-pumped solid-state laser and cooled passively by spooling it on a grooved aluminum mandrel. The amplifier produced a strongly linearly polarized output at 1064 nm in the fundamental mode (M2 ≤ 1.2) with a 150 kHz linewidth and a power of 81.5 W for 107 W of launched pump power. No deleterious effects from the elevated thermal load were observed. The residual photodarkening loss resulting from the high Yb concentration, found to be small (~0.7 dB/m inferred at 1064 nm) with accelerated aging, reduced the output power by only ~20% after 150 h of operation.

Experimental characterization of bending effects for solid and hollow dielectric waveguides at V-band

Mm-wave dielectric waveguides are a promising and low-cost technology for the transmission of ultra-high data rates. Besides the attenuation (losses) and group delay, the bending loss of the dielectric waveguides is also one of the key parameters to establish the capacity and energy efficiency of such wired links, when deployed in realistic scenarios. In this context, we report the experimental characterizations of bending effects for various solid and hollow commercially available dielectric waveguides at V-band (50–75 GHz). A wide-band transition has been designed to carry out the measurements using a Vector Network Analyzer (VNA) and extension modules. The measured results are in very good agreement with full-wave simulations. Our experimental results show an average bending loss of 1.46 dB over the entire V-band for the fundamental $${HE}_{11}^{y}$$ HE 11 y mode of a PTFE solid dielectric waveguide (core diameter of 3.06 mm) with a 90° bending angle and 25 mm radius of curvature. This value rises up to 2.88 dB (or 3.25 dB) when bending radius is changed to 15 mm (or bending angle grows up to 140°). The measurements also show that the measured bending losses increase significantly for hollow dielectric waveguides, in particular when the inner to outer diameter ratio gets larger.

Single-mode Optical Fiber: An Investigation for the Bending Loss at Wavelength 650 nm

In modern time, the optical fiber communication has revolutionized the data transmission process and contributed vitally to the development of qualitative and speedy telecommunication systems. The arteries of this system are optical fibers which carry information as light signals and as fast as speed of light. But these light signals suffer energy losses during their propagation through the optical fibers. For the effective functioning of an optical fiber communication, it is necessary to know and prevent the prevailing energy losses (especially external bending losses) of the optical fibers. In this paper, the external bending loss of optical power while propagating through a single-mode optical fiber has been investigated. Further, the effects of wrapping turns (1 to 6 turns) and bending diameters (2 cm ≤ D ≤ 12 cm) on the power loss of laser at a wavelength of 650 nm have been studied. Keywords: Single-mode optical fiber, Bending loss, Attenuation coefficient, Wrapping turns, Bending diameter. PACs: 42.81.-I, 78.67.Pt, 42.25.Bs.

Epsilon Near Zero (ENZ) Based Kagome Photonic Crystal Fiber for Low Loss, High Birefringence and Near Zero Flat Dispersion in THz Regime

In this research, we have proposed two novel types of Kagome PCFs one is slotted core PCF (S-KPCF) and another one is circular PCF (C-KPCF). FEM has been applied with boundary condition to investigate the optical properties of Proposed PCFs. HRS material along with Epsilon Near Zero (ENZ) material has been applied in core and TOPAS was used as background material. Numerical investigation takes place a wider frequency range for 0.8 THz to 2 THz. Slotted core PCF (S-KPCF) shows eminent birefringence of 2.98×10− 2, Lower EML of 0.232 cm− 1, lower confinement loss of 2.76×10− 8, Bending loss 10.76×10− 9, Total loss of 0.232cm− 1 at frequency 1THz. Besides circular core PCF (C-KPCF) shows eminent birefringence of 8.69×10− 2, Lower effective material loss of 0.746 cm− 1, lower confinement loss of 2.80×10− 7, Bending loss 7.76×10− 9, Total loss of 0.746cm− 1 at 1THz. Both PCFs show flat dispersion near zero (for S-KPCF is -0.997ps/nm/Km and for C-KPCF is -0.797ps/nm/Km) range. V-Parameter of both of the PCF indicates that both PCF is multimode PCF. Comparison of the proposed PCFs shows that C-KPCF shows better results than S-KPCF and both PCFs shows better results than previous PCFs.

Design and Analysis of Trench-Assisted Low-Bending-Loss Large-Mode-Field-Area Multi-Core Fiber with an Air Hole

In this paper, a trench-assisted low-bending-loss large-mode-field-area multi-core fiber with air hole is proposed, which can achieve dual-mode transmission. The influence of structural parameters on fiber performance is analyzed systematically, and the structure of the trench, with a lower refractive index than the cladding, is also analyzed and optimized. By adjusting the structural parameters, the effective mode field area of the fundamental mode can reach 2003.24 um2 at 1550 nm, and when the bending radius is 1 cm, the bending loss is 2.57 × 10−3 dB/m. The practical implementation of the proposed fiber is feasible using existing fabrication technology and is applicable to the transmission of large-capacity optical communication systems and high-power lasers.