• Journal of the Optical Society of Korea
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• v.11 no.3
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• pp.113-117
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• 2007

A LED light coupler is proposed for coupling light from a mini side LED of 0.4 mm height to a very thin (${\sim}0.3 mm$) light guide. Due to the ultra thinness of the light guide, conventional light couplings between LEDs and light guides do not provide adequate coupling efficiency. The designed LED coupler is a compound lens of 3.5 mm length, 1.2 mm height, and 3.3 mm width. The courier first collimates the light from the LED and then concentrates the light in a manner similar to a compound parabolic concentrate, (CPC) into the light guide. The exit surface of the coupler is additionally textured to have micro patterns in order to control the radiance profile.

• Korean Journal of Optics and Photonics
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• v.18 no.5
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• pp.295-302
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• 2007

This paper presents a rigorous comparison of the design characteristics of polarization-insensitive directional coupler (DC) and multimode interference (MMI) coupler based on rib type waveguides, by using longitudinal modal transmission-line theory (L-MTLT). It shows that the multimode mixing and interference property of MMI can be structurally designed through the continuous evolution of the two-mode coupling property of DC. It also compares and analyzes the coupling efficiency along with the coupling length and the wavelength between polarization-insensitive DC and MMI. From the design properties obtained, it demonstrates for the first time the integration of polarization-insensitive DC or MMI with a Bragg grating and evaluates precisely the filtering characteristics. The numerical results reveal that the DC, as long as it is designed to have the same coupling length for TE and TM modes, has better performance than the MMI in polarization-insensitive filtering behaviour. However, it shows that the MMI with much less coupling length than DC is preferred in the miniaturization of integrated devices.

• Journal of Advanced Navigation Technology
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• v.13 no.2
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• pp.194-200
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• 2009

This paper introduces a ring hybrid coupler using shunt capacitors, high impedance lines and CRLH-TLs (Composite Right/Left-Handed Transmission Lines) with size reduction and bandwidth enhancement. The reduced method of line length uses to combine a short length high impedance line and shunt capacitors. Also, there is combined CRLH meta-material so as to obtain wide bandwidth of transmission line using nonlinear phase characteristic of CRLH-TL that consists of series capacitors and shunt inductors. The implemented ring hybrid coupler shows a novel design with compact size that is smaller than 10% and bandwidth is larger than 60% of conventional ring hybrid coupler.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2016.10a
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• pp.85-88
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• 2016

Two output ports of $90^{\circ}$ hybrid-coupler are generally the same output power with $90^{\circ}$ phase difference. But, Two output ports of $90^{\circ}$ hybrid-coupler must be the different output slope characteristic about frequency because of the different electrical length. In $90^{\circ}$ hybrid-coupler being the same power distribution, 3-dB power distribution at two output ports only exists near the center frequency. And, the output power difference between two output ports increases in accordance with the further away from the center frequency. This paper proposes $90^{\circ}$ hybrid-coupler being the similar output slope characteristic of two output ports in wideband to modify the ${\lambda}/4$ transmission line of $35-{\Omega}$ characteristic impedance between input port and output port near input port. The power difference between two output ports of the proposed circuit is below 0.2dB over 20% bandwidth of the center frequency in ADS(advanced Design System).

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.11
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• pp.29-34
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• 2008

The propagation characteristics of novel grating-assisted multimode interference (GA-MMI) coupler are explicitly and theoretically investigated by using longitudinal modal transmission-line theory (L-MTLT). The coupling efficiency of GA-MMI coupler is evaluated along the variation of grating thickness and duty cycle, and the spectrum is analyzed numerically. The numerical results reveal that the coupling length and the efficiency of $2{\times}2$ GA-MMI coupler along the variation of grating structure have low tolerance and the bandwidth varies dramatically along the output states.

• 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.

• Proceedings of the Optical Society of Korea Conference
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• 1990.02a
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• pp.219-221
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• 1990

Y-branch directional coupler type optical modulators with three different coupling lengths were fabricated on z-cut LiNbO3 and tested at λ-1.3${\mu}{\textrm}{m}$. One device gad an exact coupling length for complete power transfer and two other devices had coupling lengths. It was confirmed that, for dc operation, experimental results agreed well with theoretical results.

• 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.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.4
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• pp.11-19
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• 2022

In this study, in order to improve the splice performance of mechanical couplers, two new mechanical couplers with different connection modes were developed with rebar(SD400). The stress analysis of mechanical couplers with two different connection modes was carried out. Uniaxial tensile tests were carried out with type of steel, connection mode and the slope length of internal fastener as variables to analyze the influence on the maximum tensile strength. Building upon this previous work, the specimens that met the code in uniaxial tensile test were fabricated and static loading test and cyclic loading test were performed on the basis of Korean code(KS D 0249). The results of this research are as follows; (1) The tensile strength of steel and the slope length of internal fasteners have a certain influence on the maximum tensile strength. (2) The connection mode has some influence on the stiffness, slip and stiffness reduction rate of the connecting rebars. The results verify the feasibility of the proposed enhanced mechanical coupler in the field.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.5
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• pp.510-515
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• 2011

In this paper, an artificial transmission line coupler with slotted-triangular patches, which is compact and spacesaving structure, is proposed. The proposed structure has specific features of not only convenience for adjusting the characteristic impedance and the phase of its coupled line by varying the lengths of the slots of the artificial transmission lines in designing a coupler but also the maximized coupling value at less than ${\lambda}$/4 electrical length so that it can be designed in compact and small dimensions, while conventional coupled line couplers are generally limited in compact and miniaturized designs by their ${\lambda}$/4 transmission lines. A fabricated 15 dB test-coupler at 2.4 GHz band by proposed design method shows good agreement with theory and simulation.