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Input/Output bending 영역에서의 parasitic coupling을 고려한 방향성 결합기 광 스위치의 설계 법칙
김동각,김창민 대한전자공학회 1997 電子工學會論文誌, D Vol.d34 No.1
Design rules of directional coupler optical switches are discussed in consideration of parasitic couplings in the bending section. The parasitic coupling phenomenon is analyzed based on the coupled-mode theory and the solutions are represented in the form of the transfer matrix. The modified switching conditions due to the parasitic coupling are derived and the resultant switching diagrams are illustrated. It is revealed that the parallel section's length needs to be adjustd less than the coupling length $l_c(=\pi/2\textsc{k}o)$ to obtain the desired crosstalk and that the adjustment depends on the strength of the parasitic coupling. However, it is discovered that, for weak parasitic coupling, the switching voltage does not need to be altered but may maintain the same value as if no parasitic coupling is taken into account.
λ=1.55 ㎛에서 포물선분포 - 이중클래드, 분산보상 단일모드 광섬유의 설계
김동각(Dong-Gak Kim),김창민(Chang-Min Kim),이상배(Sang Bae Lee),강희전(Hee Jeon Kang) 한국광학회 1997 한국광학회지 Vol.8 No.2
기존의 λ=1.31 ㎛에서 분산 최적화된 광통신시스템을 λ=1.55 ㎛ 광전송시스템으로 향상시키는데 필요한 분산보상 단일모드 광섬유(DCF)를 설계하였다. 총분산이 λ=1.55 ㎛에서 큰 마이너스 분산치를 갖는 굴절율 분포를 얻기 위해 포물선분포-이중클래드 광섬유의 분산특성을 해석하였다. 광섬유 스칼라 파동방정식으로부터 분산특성을 얻기 위해 1차원 유한요소법을 적용하였다. Reel에 감긴 DCF의 macro-bending에 의한 손실을 적절히 제한하기 위해, LP_(01)모드의 차단 파장이 λ=1.80 ㎛이상이 되도록 설계하였다. 이 조건에 맞는 굴절율분포의 λ=1.55 ㎛에서 분산의 하한치는 약 -120 ㎰/㎚ㆍ㎞ 정도로 제한됨을 볼 수 있었다. We design the single mode dispersion-compensating fibers (DCF) which may be necessary for upgrading the previously installed 1.31 ㎛ optical communication system to the 1.55 ㎛ system. To obtain the optimum index profile that allows large negative dispersion at 1.55 ㎛, parabolic-index, double-clad fibers are analyzed by applying the 1-D FEM to the scalar wave equation of optical fibers. In consideration of macro-bending loss, the fibers are designed so that the cutoff wavelength of the LP_(01) mode is greater than 1.80 ㎛. The computer simulations show that the lower bound of the dispersion at 1.55 ㎛ is limited to about -120 ㎰/㎚ㆍ㎞ for the fiber index profiles satisfying the LP_(01)'s cutoff condition.
LD gain-switching에 의한 초단 광 펄스 발생 해석
김윤중,김동각,김창민 대한전자공학회 1997 電子工學會論文誌, D Vol.d34 No.10
For a InGaAsP buried - heterostructrue $1.3\mu\textrm{m}$ LD with fabry-perot cavity structure, the procedures of ultra-short optical pulse genration ar eanalyzed by simulating the rate equations. Investigting the effects of injected current pulse parameters such as bias $J_b$, pulse width $T_d$ and pulse amplitude $J_p$ on the generated optical pulses, we derive the optimum conditions to obtain a single optical pulse with strong peak value. We also observe that the repetition rate of current pulses needs to be restricted under a certain threshold to generate a train of single optical pulses, and that the period doubling phenomenon takes place by increasing the repitition rate.