• Title/Summary/Keyword: Optical coupler

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A Study on the Optimization of the Optical Coupler for Wavelength Division (파장 분할 광 결합기의 최적화에 관한 연구)

  • 윤성현;정만영
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.14 no.2
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    • pp.177-187
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    • 1989
  • When wavelength division optical coupler is fabricated with the polished single mode optical fiber, coupling coeffiecient differ from wavelength and distance to two cores. Wavelength division is function of the differential coupling coefficient to distance of two cores. This paper suggests the condition of the minimum spacing of the wavelength division with the function of the distance of two cores.

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Compact and Temperature Independent Electro-optic Switch Based on Slotted Silicon Photonic Crystal Directional Coupler

  • Aghababaeian, Hassan;Vadjed-Samiei, Mohammad-Hashem
    • Journal of the Optical Society of Korea
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    • v.16 no.3
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    • pp.282-287
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    • 2012
  • In this paper, we have proposed a principle to design a compact and temperature independent electro-optic switch based on a slotted photonic crystal directional coupler (SPCDC). Infiltration of the slotted silicon photonic crystal with polymer enhances the slow light and decreases the switching length, whereas the different signs of thermo-optic coefficients of the polymer and silicon make the proposed switch stable within $25^{\circ}C$ to $85^{\circ}C$ temperature range. The SPCDC structure is modified to increase poling efficiency of the polymer in the slot and to flatten the dispersion diagram of the even mode to minimize the switching length.

Optical IIR lattice fiber filter design for optimum of optical signal energy (광신호 에너지 최적화를 위한 IIR 격자형 광파이버필터 설계)

  • 이채욱;김신환
    • Journal of the Korean Institute of Telematics and Electronics B
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    • v.32B no.11
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    • pp.1481-1488
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    • 1995
  • Due to the low loss, broadband and accurate short time delay properties of optical fiber, it has attracted as a delay medium for high speed and broad-band signal processing. In this paper, we consider the coherent optical fiber filter of IIR lattice structure, which uses coherent light sources and consists of directional couplers whose coupling coefficients are restricted between 0 and 1. Considering restrictions of directional coupler, the design formulae and condition for realibility of optical fiber filter of IIR lattice structure which makes the optimal use of optical signal energy are derived.

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Soliton coupler using a bent nonlinear waveguide (굽은 비선형 도파로를 이용한 솔리톤 결합기)

  • 정준영;강병한;정제명
    • Korean Journal of Optics and Photonics
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    • v.10 no.6
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    • pp.487-493
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    • 1999
  • In this paper, we studied the characteristics of a soliton coupler using a bent nonlinear waveguide. The bent soliton coupler has very ,harp switching characteristic like the conventional soliton coupler due to the threshold effect of soliton emi,sion from the nonlinear waveguide. By using the bent structure, we can reduce the threshold power for the soliton emission. We consider the saturation effect of nonlinearity and the loss in the medium for more accurate and practical numerical analysis in wave propagation through the bent soliton coupler. The simulation results show that the consideration of the saturation effect and the ]os~ may be very important in the analyses and design of the nonlinear waveguide devices. The bent structure is useful for the emission of the spatial soliton with the low threshold power, when we consider the saturation and the loss effect. ffect.

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A Study on a Compact Coupler between an Optical Fiber and a Grating-assisted Graphene-embedded Silicon Waveguide for a Wavelength-selective Photodetector

  • Heo, Hyungjun;Kim, Sangin
    • Current Optics and Photonics
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    • v.1 no.5
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    • pp.514-524
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    • 2017
  • We proposed an integrated wavelength-selective photodetector based on a grating-assisted contradirectional coupler and a graphene absorption layer for a coarse wavelength division multiplexing (CWDM) communication system. The center wavelength of the absorption spectrum of the proposed device can be tuned simply by changing the period of the grating, and the proposed device structure is suitable to forming a cascaded structure. Therefore, an array of the proposed device of different grating periods can be used for simultaneous wavelength demultiplexing and signal detection in a CWDM communication system. Our theoretical study showed that the designed device with a grating length of $500{\mu}m$ could have an absorption of 95.1%, an insertion loss of 0.2 dB, and a 3 dB bandwidth of 7.5 nm, resulting in a -14 dB crosstalk to adjacent CWDM channels. We believe that the proposed device array can provide a compact and economic solution to receiver implementation in the CWDM system by combining functions of wavelength demultiplexing and signal detection.

Low-loss Electrically Controllable Vertical Directional Couplers

  • Tran, Thang Q.;Kim, Sangin
    • Current Optics and Photonics
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    • v.1 no.1
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    • pp.65-72
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    • 2017
  • We propose a nearly lossless, compact, electrically modulated vertical directional coupler, which is based on the controllable evanescent coupling in a previously proposed graphene-assisted total internal reflection (GA-FTIR) scheme. In the proposed device, two single-mode waveguides are separate by graphene-$SiO_2$-graphene layers. By changing the chemical potential of the graphene layers with a gate voltage, the coupling strength between the waveguides, and hence the coupling length of the directional coupler, is controlled. Therefore, for a properly chosen, fixed device length, when an input wave is launched into one of the waveguides, the ratio of their output powers can be controlled electrically. The operation of the proposed device is analyzed, with the dispersion relations calculated using a model of a one-dimensional slab waveguide. The supermodes in the coupled waveguide are calculated using the finite-element method to estimate the coupling length, realistic devices are designed, and their performance was confirmed using the finite-difference time-domain method. The designed $3{\mu}m$ by $1{\mu}m$ device achieves an insertion loss of less than 0.11 dB, and a 24-dB extinction ratio between bar and cross states. The proposed low-loss device could enable integrated modulation of a strong optical signal, without thermal buildup.