• 한국전기전자재료학회논문지
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• 제13권12호
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• pp.1051-1057
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• 2000

A traveling-wave CPW(coplanar waveguide) electrode with abruptly broken input/output-taper for LiNbO$_3$optical modulator was designed and fabricated. The electrical characteristics of traveling-wave electrode on z-cut LiNbO$_3$crystal with SiO$_2$buffer layers were measured by network analyzer. To confirm the possibility of the electro-optic modulator electrode, detailed calculations of the impedance, microwave effective index and attenuation constants are presented as a function of the microwave electrode thickness, but the buffer layer thickness is fixed as 1${\mu}{\textrm}{m}$. These characteristics are discussed from the viewpoint of the device optimization and are expected to be design guides for the LiNbO$_3$modulator’s electrodes.

• Journal of the Optical Society of Korea
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• 제15권3호
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• pp.227-231
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• 2011

An external optical modulation using absorption s in a Fabry-Perot laser diode (FP-LD), has been proposed and experimentally demonstrated for multicasting in a WDM-PON. The center wavelengths of absorption s in an FP-LD move to short-wavelength rapidly by only a small current (~1 mA) injection. If the current injection is stopped, the s move back to the original position. Such a movement of the s can make the FP-LD act as an external optical modulator, which is found to modulate at a maximum modulation speed of 800 Mbps or more. For a multicasting transmitter in a WDM-PON, the proposed modulator can be cost-effectively applied to a multi-wavelength laser source with the same periodicity of the longitudinal mode. Instead of the multi-wavelength laser source, tunable-LDs are used for experiments. The 32 channel multicasting system with the proposed modulator has been demonstrated, showing power penalties of 1.53~4.15 dB at a bit error rate of $10^{-9}$ with extinction ratios better than 14.5 dB at 622 Mbps.

• E2M - 전기 전자와 첨단 소재
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• 제11권11호
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• pp.28-36
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• 1998

Widely tunable diodes integrated with periodically sampled and chirped DBR(distributed Bragg reflector) and an EA(electroabsorption) modulator are analyzed dynamically using the improved largesinal time-domain model. The tuning characteristics of sampled- and chirped-grating DBR laser diodes are demonstrated theoretically. The results of the simulation agree well with those of the experiment. And the intensity-modulation properties of the laser diodes integrated with an EA modulator are calculated. It is shown that the external modulation has the lower frequency chirp by 1/20 for the same extinction ratio than the direct modulation, and also the short pulse train can be generated using the optical gating of an EA modulator.

• Journal of the Optical Society of Korea
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• 제18권5호
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• pp.589-593
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• 2014

Terahertz (THz) communication has important applications in high-speed and ultra broadband wireless access networks. The THz modulator is one of the key devices in a THz communications system. Wavelength division multiplexing (WDM) can expand the capacity of THz communications systems, so research on multi wavelength THz modulators has significant value. By combining photonic-crystal and THz technology, a novel type of multi wavelength THz modulator based on a triple-lattice photonic crystal is proposed in this paper. Compared to a compound-lattice photonic crystal, a triple-lattice photonic crystal has a larger gap width of 0.196. Simulation results show that six beams of THz waves can be modulated simultaneously with high performance. This modulator's extinction ratio is as large as 34.25 dB, its insertion loss is as low as 0.147 dB, and its modulation rate is 2.35 GHz.

• Journal of the Optical Society of Korea
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• 제18권5호
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• pp.564-568
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• 2014

We present a 25-Gb/s optical transmitter composed of a Si ring modulator and CMOS driver circuit. The Si ring modulator is realized with 220-nm Si-on-insulator process and the driver circuit with 65-nm CMOS process. The modulator and the driver are hybrid-integrated on the printed circuit board with bonding wires. The driver is designed so that the parasitic bonding wire inductance provides enhanced driver bandwidth. The transmitter successfully demonstrates 25-Gb/s operation.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2016년도 춘계학술대회
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• pp.698-701
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• 2016

본 논문에서는 Current Modulator를 이용하여 루프 필터 커패시턴스 유효 용량을 배가 시켜 칩 크기를 줄일 수 있는 위상고정루프를 제안하였다. 제안된 위상고정루프에서는 Current Modulator로 루프 필터의 커패시턴스 유효 용량을 배가 시켜 루프 필터 커패시터 크기를 1/10로 줄였다. 제안된 위상고정루프는 1.8V $0.18{\mu}m$ CMOS 공정을 이용하여 설계되었다. 시뮬레이션 결과는 기존 구조와 같은 잡음 특성과 위상고정 시간을 보여주었다.

• International journal of advanced smart convergence
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• 제8권3호
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• pp.61-68
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• 2019

Spatial modulation (SM) is the first proposed space modulation technique. By further utilizing the quadrature spatial dimension, quadrature spatial modulation (QSM) has been developed as an amendment to SM system to enhance the overall spectral efficiency. Both techniques are capable of entirely eliminating interchannel interference (ICI) at the receiver. In this paper, we propose a simple adaptive hybrid switching transmission scheme to obtain better system performance than SM and QSM systems under a fixed transmission date rate. The presented modulator selection criterion for switching between spatial modulator and quadrature spatial modulator is based on the larger received minimum distance of spatial modulator and quadrature spatial modulator to exploit the spatial channel freedom. It is shown through Monte Carlo simulations that the proposed hybrid SM and QSM switching system yields lower error performance than the conventional SM and QSM systems under the same fixed data rate and thus can provide signal to noise ratio (SNR) gain.

• 대한기계학회논문집A
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• 제28권12호
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• pp.1990-1996
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• 2004

This paper presents a nonlinearly modulated digital actuator (NMDA) for producing nano-precision digital stroke. The NMDA, composed of a digital microactuator and a nonlinear micromechanical modulator, purifies the stroke of the digital actuator in order to generate the high-precision displacement output required for nano-positioning devices. The function and concept of the nonlinear micromechanical modulator are equivalent to those of the nonlinear electrical limiters. The linear and nonlinear modulators, having an identical input and output strokes of 15.2${\mu}{\textrm}{m}$ and 5.4${\mu}{\textrm}{m}$, are designed, fabricated and tested, respectively. The linear and nonlinear modulators are linked to identical digital actuators in order to compare the characteristics of the linearly modulated microactuator (LMDA) and NMDA. In addition, an identical linear modulator is attached to the output ports of LMDA and NMDA. The NMDA shows the repeatability of 12.3$\pm$2.9nm, superior to that of 27.8$\pm$2.9nm achieved by LMDA. When the identical linear modulator is connected to LMDA and NMDA, the final modulated output from NMDA shows the repeatability of 10.3$\pm$7.2nm, superior to that of 15.7$\pm$7.7nm from LMDA. We experimentally verify the displacement purifying capability of the nonlinear mechanical modulator, applicable to nano-precision positioning devices and systems.

• 한국광학회지
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• 제7권3호
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• pp.280-286
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• 1996

본 논문에서는 자기 전광 효과를 이용하여 광쌍안정을 갖는 새로운 형태의 도파로형 광변조기의 동작 특성에 관하여 논하였다. 제작된 소자는 전계의 세기에 따른 굴절률의 변화를 이용하는 위상 변조형 광변조기와 전기적 쌍안정성을 갖는 수광 소자가 병렬로 연결된 구조로 되어 있다. 광도파로층과 수광 소자의 흡수층은 GaAs/AlGaAs 다중 양자 우물층을 사용하였다. 수광 소자에 흡수되는 광의 세기에 따라 변하는 다이오드 전압은 도파로형 광변조기를 통과하는 광의 세기를 조절하며 SEED의 전기적 쌍안정을 이용하여 도파로형 광변조기의 광쌍안정을 얻을 수 있었다. 본 논문에서 제안된 광변조기는 기존의 도파로형 광변조기에 비해 낮은 입력광에서도 광안쌍정을 갖는 장점을 갖는다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 E
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• pp.1779-1781
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• 1997

The 2.0 GeV Pohang Light Source (PLS) is consisted of a full energy Linac and a storage ring. Four kicker magnets are installed in the storage ring tunnel to move the stored beam orbit in the storage ring closer to the injected beam from the beam transfer line. The injected beam then falls into the storage ring beam dynamic aperture. A kicker magnet modulator drives all four kicker magnets to maintain field balance and also synchronized kick of the beam. The kicker modulator can handle 2 GeV full energy beam. The kicker magnet modulator is installed in the storage ring tunnel and under stable operation. Specification of the kicker magnet modulator is ${\sim}6.0{\mu}s$ pulse-width, 200 ns flat-top width with ${\pm}0.2%$ regulation, ${\sim}24\;kA$ peak current, and 10 Hz repetition rate. Two thyratron switches (EEV CX-1536AX) are used in the system. In this article, design, and experimental results of the kicker magnet modulator are discussed.