• Korean Journal of Optics and Photonics
• /
• v.25 no.3
• /
• pp.146-149
• /
• 2014

The homogeneous line broadening in EDF leads to unstable lasing and strong mode competition. In this paper a multiwavelength fiber ring laser that overcomes these effects by using variable attenuators between the DWDM and $1{\times}N$ coupler, has been proposed. Fiber ring lasers with four and eight wavelength outputs are implemented, and we show that the output powers can be adjusted with stable operation. The EDF ring laser has one four-wavelength output and four of single wavelengths, with OSNR of 50 and 60 dB respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2006.11a
• /
• pp.239-240
• /
• 2006

저손실 고투자율 특성을 가지는 ${\alpha}-Fe$ 나노결정 자심재료를 제조하기 위한 열처리 온도 변화에서, $510^{\circ}C$의 열처리 조건에서 가장 높은 투자율과 신호전송 특성을 나타내었다. 저주파 대역에서의 신호 전송 특성은 자심재료의 자기적 특성에 지배적인 영항을 받으며, 고주파 대역의 신호전송 특성은 임피던스 매칭으로 향상시킬 수 있었다. 그리고 커플러의 출력부에 신호증폭장치를 삽입하여 자기유도에 의해 신호가 커플링될 때 발생하는 삽입손실을 보완하여 커플러의 특성을 향상시킬 수 있었다.

• Korean Journal of Optics and Photonics
• /
• v.15 no.1
• /
• pp.28-33
• /
• 2004

An in-line fiber coupler, based on side-polished single-mode fibers covered with an intermediate coupling layer and a planar waveguide, is analyzed by modeling the interaction region as an equivalent multi-layered planar waveguide. The reflectance for the multi-layered structure with and without buffer layer is illustrated as a function of the refractive index and thickness of the overlay waveguides. When the refractive index of the overlay waveguides is greater than that of the fiber core, the conditions for the intermediate coupling layer to increase the power coupling from the fiber to the overlays is also explained. Through the experimental results using a LiNbO$_3$planar waveguide, we show that the theoretical analysis is reasonable and in good agreement with the measured values.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.12 no.4
• /
• pp.335-346
• /
• 1987

The principal reason for the backscattering in an optical fiber is the Rayleigh scattering which is caused by non-uniform density of structure material of an optical fiber and diameter variations of the optical fiber-core along an optical fiber axis. The backscattering signal which is detected by the optical time domain reflectometer system(O.T.D.R) conatains information about both tha actual decay of power and the diameter variation along the optical fiber. In this paper, the O.T.D.R. system with 2x2 fiber directional coupler, timing control unit and gated integrator is used to measure diameter variations of an optical fiber.

• Proceedings of the KIEE Conference
• /
• 2002.07c
• /
• pp.1674-1676
• /
• 2002

In this paper, High Frequency PD measuring system using directional coupler sensors(DCS) is introduced. Especially the principles of the DCS and characteristics of the system are introduced. Evaluation of this system was carried by an adoption to the test circuit of 345kV XLPE $2000mm^2$ cable and EB-A, EB-G, PIJ, PNJ. In the test a PD measurement was carried out without shieldroom and under the on-line state and in the high frequency range at the remote site from the test object. The test result was satisfactory and this is due to the use of DCS and using a high frequency range and specific filter for radio and TV signal and low pass. This system can be used to the test of a new construction of cable and accessories and measuring of long-term deterioration of cable and accessories. And this will bring us the reliability of a power transmission.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.14 no.12
• /
• pp.1335-1340
• /
• 2003

In this paper, a single balanced diode Mixer for the homodyne FMCW radar to detect distance and velocity of a vehicle target is designed and implemented using a microstrip line and two schottky barrier beam lead diodes. This mixer is optimally designed to have less a conversion loss within the 100 MHz bandwidth with a little LO injection power and a higher LO isolation as soon as possible through the embedded electrical length of microsrtrip line placed between the coupler and diode matching, considering together LO matching condition. The measured results show 6 dB of conversion loss, 23 dB LO/RF isolation and 3 dBm of input 1l dB, respectively.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.34 no.2A
• /
• pp.139-146
• /
• 2009

This paper presents an average internal loop-back antenna calibration method for array antenna in TDD(Time Division Duplex) systems. The proposed method calibrates the amplitude and the phase of RF systems using into mal coupler and switches without aids of external calibration systems. The average calibration scheme of the proposed method also increases reliability of calibration performance. Computer simulation demonstrates that the proposed method corrects beamforming angles of DOA estimation algorithm and BER performance in transmit power allocation scheme.

• Korean Journal of Optics and Photonics
• /
• v.25 no.2
• /
• pp.90-94
• /
• 2014

We propose a Yb:YAG laser Q-switched by a semiconductor saturable absorber and a laser output coupler composed of a polarizer and a quarter-wave plate, and we investigate the output characteristics of the proposed Q-switched laser. We show that the laser power can be varied by rotation of the quarter-wave plate.

• Proceedings of the KIEE Conference
• /
• 2004.07c
• /
• pp.1860-1862
• /
• 2004

It is widely known that the ultra high frequency (UHF) method that detects the electromagnetic wave of the PD pulses in the gas insulated space is one of the most competitive methods for its high sensitivity. From the above point of view, this paper describes the characteristics of GIS PD signals measured with ultra wide band (UWB) GIS PD detecting system in which PD signals are detected into the dual UHF band. The UWB PD detection system consists of the UWB UHF coupler, the UWB low noise amplifier (LNA) and the oscilloscope. The dual bands for PD signals are 0.5-2GHz(full band) and 1-2GHz(high band). As results, it was found that the partial discharges of each defect have their own characteristic pattern and the ratio of High band to Full band increases with gas pressure.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2010.06a
• /
• pp.161-161
• /
• 2010

In order to achieve low power consumption and the uniform power spectrum of LED BLU (Back Light Unit) system, new circuits with a 2 stage L-C (Inductor-Capacitor) coupler have been proposed. From the simulation results based on our proposed model, the ripple power of the L-C regulation-embedded BLU circuit shows a dramatic reduction by more than 89.3% as compared to the normal BLU (without L-C circuits). This indicates that the proposed circuit is very promising for the realization of high-efficiency BLU circuits.