Multimode Bend Research Articles

A Study of the Flexural Properties of Jute Fabric Reinforced Epoxy Composite: Experimental and Uncertainty Analysis

ABSTRACT The variability in natural fiber composite properties has always been problematic due to the dispersion in their mechanical properties resulting from fiber misalignment, irregular crosssection, fiber length, and geometry, which impacts their reliability. This issue of reliability has greatly affected the selection process of natural fiber composites as opposed to the synthetic fiber counterparts when it comes to strength, stiffness, failure strains, and energy absorption criteria. Stiffness is one property which greatly depends on the span length and load-bearing capacity of the material, which makes it an important criterion during product design. In this study, flexural properties of the jute fabric composite were studied through experiment and uncertainty analysis using various distribution functions. Jute epoxy composite at 38% fiber volume fraction was fabricated, and samples were machined using abrasive water jet machining as per ASTM D7264 standard for bend test. The samples were experimentally tested for bending strength, modulus, and failure strains, and uncertainty analysis was done to further analyze their failure behavior. Experimentally tested samples showed multimode bending failure such as M(CAT) and M(TAB) as per ASTM D7264.

Subwavelength Grating Metamaterial Multimode Bend for Silicon Waveguides

AbstractIn this paper, a novel multimode waveguide implemented on a silicon‐on‐insulator (SOI) platform that supports several transverse (TE)/transverse magnetic (TM) modes across a broad range of wavelengths is experimentally demonstrated. The fully etched metamaterial design combines a gradient curvature bend with trapezoidal subwavelength grating segments and tapered concentric bridging strips. The simulations showed successful propagation of up to nine modes (5 TE and 4 TM) on the 340 nm SOI platform, with excess losses below 2.4 dB, and intermodal cross‐talk of less than −15.7 dB. Experimentally, a compact multimode bend with a radius of 10 µm on a 220 nm SOI platform is demonstrated that successfully supports four TE modes, with average signal‐to‐cross‐talk extinction ratio levels of 14.4 dB or better, across a wavelength band of 1500–1600 nm. This versatile multimode waveguide bend can be employed as a fundamental building block for densely integrated photonic circuits and mode multiplexing systems.

Design of an ultrasharp silicon multimode waveguide bend assisted by multiregional subwavelength grating structures

Sharp multimode waveguide bends are beneficial to improve the integration density of the on-chip mode-division multiplexing (MDM) systems, which can be used to increase the optical information transmission capacity. A method of designing a multimode bending structure based on subwavelength gratings is proposed in this paper, through the mode conversion and matching between the straight and bending waveguide. The proposed bending structure is composed of a 90-deg arc-bend with a radius of 5 μm combined with the shallow-etched grating structures on the top, and two-mode converters on the input and output straight waveguide realized also with the help of nonuniform grating-like structures, achieving a total effective bending radius of 8.25 μm and high transmission efficiencies of the first three TE modes (TE0 − TE2) in a wide wavelength range of 1500 to 1600 nm. At the center wavelength of 1550 nm, the calculated excess losses of the three modes TE0, TE1, and TE2 are 0.21, 0.19, and 0.59 dB, respectively, and the crosstalks for all modes are less than −26.58 dB. More importantly, we add a non-uniform grating converter in the straight waveguide region which pre-deviates the mode fields inside the straight waveguide to help further reduce the size of the bending part to only 5 μm, which will be helpful for large scale integration when a great number of bends are cascaded.

Propagation of fundamental mode in regularly bending multi-mode waveguides

Transmission of the fundamental mode in multi-mode waveguides is an effective scheme for a silicon-based platform to reduce scattering loss. However, the application of the scheme is usually limited to straight waveguides and restricted in multi-mode bending waveguides. This is because the fundamental mode of a straight waveguide is seriously disordered after passing the bend. In this work, we have presented a “matched bending radius” approach, by which an ultra-low loss and negligible modal disorder have been demonstrated in the Si and Si3N4 multi-mode waveguides. The estimated TE0 mode transmission factor is almost 0 dB at the matched bending radius, indicating that the fundamental mode can be re-generated after passing the multi-mode bending waveguide. The proposed approach will contribute to applying the low loss scheme in large-scale photonic integrated circuits.

SOI multimode waveguide bend with radially bridged SWGs for broadband (de)multiplexing -INVITED

A novel broadband multimode waveguide bend is proposed that supports the propagation of multiple TE modes on a silicon-on-insulator platform. The gradient curvature bend utilizes trapezoidal subwavelength grating (SWG) segments, connected by adiabatically tapered radial strips to achieve efficient mode (de)multiplexing. The inclusion of the radial strips offers an extra degree of design freedom, allowing the realization of a multimode bend with only one single full etch step. The access waveguide has a width of 2.075 μm with an effective radius of 10 μm. Propagation loss for all modes remains below 2.96 dB, and intermodal crosstalk has a maximum of -19 dB across a broad bandwidth of 100 nm, centred at 1550 nm. This work presents an excellent design choice for broadband mode-division multiplexing operations.

Compact and broadband multimode waveguide bend by shape-optimizing with transformation optics

Multimode waveguide bend is one of the key components for realizing high-density mode-division multiplexing systems on chip. However, the reported multimode waveguide bends are either large, bandwidth-limited or fabrication-complicated, which hinders their applications in future high-density multimode photonic circuits. Here we propose a compact multimode waveguide bend supporting four TE modes simply by shape-optimizing with transformation optics. The shape of the waveguide is optimized in the virtual space with gradient distribution of the refractive index, so that the scattering loss and intermode cross talk are well suppressed. After conformal mapping back into the physical space, a compact (effective radius of 17 μm) multimode bending waveguide is obtained. Simulations show that the proposed multimode waveguide bend has little loss ( < 0.1 dB ) and low cross talk ( < − 20 dB ) throughout an ultrabroad wavelength range of 1.16–1.66 μm. We also fabricated the shape-optimized multimode bending waveguide on a silicon-on-insulator wafer. At 1550 nm wavelength, the measured excess losses for the four lowest-order TE modes are less than 0.6 dB, and the intermode cross talks are all below − 17 dB . Our study paves the way for realizing high-density and large-scale multimode integrated optical circuits for optical interconnect.

Ultra-compact bent multimode silicon waveguide with ultralow inter-mode crosstalk.

We propose and experimentally demonstrate a sharply bent multimode silicon waveguide by introducing a pair of mode converters. The principle of the multimode bend is based on the eigenmode conversion between straight and bent waveguides, and the particle swarm optimization is adopted to engineer the geometry. The device is fabricated on the standard silicon-on-insulator platform using one lithography/etching, and no additional steps are required. The measured results show that the insertion loss is <0.2 dB, and the inter-mode crosstalk is <-22 dB with a bend radius of 5μm, from 1500 to 1600nm. A comparable performance can be achieved using a conventional scheme with 40μm radius.