• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.23 no.5
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• pp.145-150
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• 2023

Non-uniform optical taper waveguides have been widely used as devices for high-efficiency mode coupling, as they are integrated with single-mode optical fibers or photonic crystal waveguides. In this paper, we present a new platform for chemical sensing and bio-sensing using optical taper waveguides with these characteristics. The principle of operation is based on the coupling efficiency and interference properties of optical directional coupler (DC) and multi-mode interference coupler (MMIC). First, the curvature characteristics of taper sections of DC and MMIC is explained, and the design specifications of optimized taper waveguide to increase waveguide sensitivity is selected. Next, the sensor response to the change in refractive index of sensing analyte is numerically analyzed. Numerical results show that as the length of couplers increases, the effective index per change in refractive index unit (RIU) of analyte increases, and that sensitivity can be tuned using taper DC and MMIC design techniques.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.5
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• pp.175-180
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• 2019

The optical characteristics and power transfers between guiding channels of blazed grating-assisted directional coupler (B-GADC) are evaluated in detail by using novel and rigorous modal transmission-line theory (MTLT) based on eigenvalue problem. To evaluate the coupling efficiency of B-GADC, the dispersion curves as a function of the grating period and wavelength are analyzed numerically for quasi-TE and quasi-TM modes. Furthermore, symmetric, sawtooth and asymmetric grating profiles are considered to know the effect of blazing characteristics on power transfer of GADC. The numerical results show that the grating period for minimum-gap condition to obtain maximum power transfer decreases gradually as the blazed structure changes from symmetric to asymmetric profile. On the other hand, the coupling length increases reversely.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.12B
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• pp.2335-2341
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• 1999

The $2\times32$ coupler consists of Mach-Zehnder interferometer and Y branch coupler. For the designs of this coupler, three dimensional rectangular core waveguide decomposed to two-dimensional structure by the effective index method. To optimize the waveguide structure, the confinement factor was investigated with two-dimensional finite difference Beam Propagation Method. The $2\times32$ coupler fabricated by simulation with height between Mach-Zehnder arms, H=$43.6\mu\textrm{m}$(path difference $0.668\mu\textrm{m}$) was showed best characteristics. In the results of dry etching of core layer, the etching rate of core layer was above 2600${\AA}$/min, the etching ratio of SiO2 to Al mask was 30:1 and the uniformity of etching was $\pm$5%. The maximum insertion loss and the uniformity of $2\times32$ coupler were below 19.2dB, 2dB respectively.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.4
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• pp.380-386
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• 2014

In this paper, a higher-order mode coupler using coaxial-structure waveguide for Ku-band monopulse satellite tracking is proposed. The proposed higher-order mode coupler is built in a coaxial structure for compactness and weight reduction, making it suitable for mobile tracking systems. The inner circular waveguide of coaxial-structure is used to extract the fundamental mode signal and the high-order mode signal is extracted from the four slots of the outer circular waveguide and then transmitted via given stepped rectangular waveguide structure. The simulated results show that proposed higher-order mode coupler covers 250 MHz(12.75 GHz ~ 13.00 GHz) bandwidth with return loss and insertion loss characteristics. The antenna patterns of fundamental mode and higher-order mode applicable to monopulse tracking are generated successfully. Designed higher-order mode coupler using coaxial waveguide structure for Ku-band is expected to be used for high precision monopulse satellite tracking systems.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.12
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• pp.1195-1200
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• 2007

Torque of a rotating shaft has been mostly measured by strain gages combined with either a slip ring or telemetry. However, these methods have severe inherent problems like low S/N ratio, high cost, limited number of channels and difficult installation. In this paper, a new method using FBG(fiber bragg grating) sensors and a rotary optical coupler for online non-contact torque monitoring is suggested. FBG sensor can measure both strain and temperature, and has much batter characteristics than those of a strain gage. A rotary optical coupler is a optical connecting device between a rotating shaft and stationary side without any physical contact. It has been devised for transmitting light between a rotating optical fiber and a stationary optical fiber. The proposed method uses this rotary optical coupler to connect FBG sensors on the rotating shaft to instruments at stationary side. And a reference FBG sensor is also applied to compensate the insertion loss change of the rotary optical coupler due to rotation. Three FBG sensors have been fabricated in a single optical fiber. Two FBG sensors are attached on the shaft surface to measure torque and one sensor is installed at the shaft center to compensate the insertion loss change. The torque of a rotating shaft has been successfully measured by the suggested method proving its superior performance potential.

• Journal of Electrical Engineering and Technology
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• v.7 no.6
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• pp.959-964
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• 2012

Internal pressure of vacuum interrupter (VI) is one of the most important parameters in VI operation and may increase due to the outgassing from the materials inside VI or gas permeation through metal flange or ceramic vessel. The increase of the pressure above a certain level leads to the failures of switching or insulation. Therefore, an effective pressure check of VI is essential and an analysis of partial discharge (PD) characteristics is an effective monitoring method to identify the degree of the internal pressure of VI. This paper introduces a research work on monitoring the internal pressure of VI by analyzing PDs which were measured using a capacitive PD coupler. The authors have developed cost effective capacitive coupler based on the ceramic material that has an excellent insulation properties and the main component of the capacitive coupler is made by SrTiO3. Detectable internal pressure range and distinguishability of the internal pressure of VI were investigated. From the PD tests results, the internal pressure range, from $10^{-2}$ torr to 500 torr, can be monitored by PD measurements using the capacitive coupler and PD inception voltage (PDIV) follows the Paschen's law. In addition, rise time of PD pulse at 13.2kV decreases with the increase of the internal pressure of VI.

• Proceedings of the IEEK Conference
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• 2001.06b
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• pp.67-70
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• 2001

We have studied the fabrication tolerance of a fused vertical coupler switch with switching operation induced section and extinction ratio enhanced section to obtain more than 30dB extinction ratio for both cross and bar states with less than 500 ${\mu}{\textrm}{m}$ device length for various thicknesses of inner cladding layer.

• Proceedings of the IEEK Conference
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• 2003.11c
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• pp.357-360
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• 2003

In this paper, we investigated the characteristics of 4${\times}$4 thermo-optic switch using two mode interference(TMI) coupler. We designed this matrix switch by using a configuration which combines a double Mach- Zehnder interferometer(MZI) switching unit. The average extinction ratio and average excess loss of the 4${\times}$4 thermo-optic switch was 33.7dB, 0.29dB, respectively.

• The Journal of the Acoustical Society of Korea
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• v.3 no.2
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• pp.23-29
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• 1984

In this paper surface acoustic wave beam track changers using symmetric multistrip coupler are designed on the basis of the perturbation theory, and its characteristics are studied. SAW beam track changers, which have the configuratio of the periodic array of metal strips, are designed with the following specifications ; the number of strips : 140, the strip period: 0.25λ, the ratios of the strip width to the period a/p: 0.5, 0.375, 0.25, respectively, and approximately consistent with the theoretical values, and also the bulk wave mode and the 2nd-order effects are suppressed by these track changers.

• Proceedings of the Optical Society of Korea Conference
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• 2006.07a
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• pp.493-494
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• 2006

Fabrication-error tolerant directional couplers are designed and analyzed. In the wavelength region of $1.55{\mu}m$, the coupling characteristics of the 3dB coupler is 50${\pm}$4%, when the waveguide width error is ${\pm}0.2{\mu}m$.