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RISS 인기검색어
- 검색키워드
- 저자 : SunHyokChang (검색결과 6 건)
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Optimization of Operating Conditions for 112-Gb/s Polarization-Multiplexed 16-QAM Optical Modulation
Sun Hyok Chang,Hwan Seok Chung,Kwangjoon Kim IEEE 2011 IEEE photonics technology letters Vol.23 No.11
<P>In this letter, we analyze a 16-ary quadrature amplitude modulation (16-QAM) optical signal generated by applying four-level electrical signals to a single in-phase/quadrature (IQ)-modulator. The amplitude of optical output of the Mach-Zehnder modulator (MZM) in the IQ-modulator needs to be carefully adjusted, and the limited extinction ratio of MZM results in unwanted phase offset. Required optical signal-to-noise ratio is estimated in the 112-Gb/s polarization-division-multiplexed (PDM) 16-QAM signal by numerical simulations with various amplitudes of the electrical modulation signals. Optimal operating conditions are found to guarantee the best performance of the received PDM 16-QAM signal.</P>
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Impact of Quadrature Imbalance in Optical Coherent QPSK Receiver
Sun Hyok Chang,Hwan Seok Chung,Kwangjoon Kim IEEE 2009 IEEE photonics technology letters Vol.21 No.11
<P>In this letter, we present the impact of quadrature imbalance in an optical coherent quadrature phase-shift-keying (QPSK) receiver. Arbitrary conjugate misalignment was realized in all-fiber optical hybrid and two correction algorithms of quadrature imbalance, the ellipse correction method, and the Gram-Schmidt orthogonalization method, were independently applied. Bit-error-rate curves versus optical signal-to-noise ratio (OSNR) were measured for the 20-Gb/s optical QPSK signal. We show that OSNR penalty is reduced from ~6 to 1 dB at ~20deg conjugate misalignment with the help of correction algorithms.</P>
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Performance of Bipolar Optical Spectral Encoding CDMA with Modified PN Codes
Sun Hyok Chang,김봉규,Heuk Park,Won Kyoung Lee,김광준 한국전자통신연구원 2006 ETRI Journal Vol.28 No.4
Experimental demonstration of bipolar spectral encoding code-division multiple-access with modified pseudorandom noise codes is presented. Bipolar spectral encoding is achieved with an erbium-doped fiber amplifier amplified spontaneous emission source and arrayed waveguide gratings. The bit-error rate performance of 1.25 Gbps signal transmission over 80 km single mode fiber is measured in a multiple-user environment.
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정환석,SunHyokChang,이종현,김광준 한국전자통신연구원 2012 ETRI Journal Vol.34 No.6
Transmission performances of direct detection-based 100-Gb/s modulation formats are investigated and compared for metro area optical networks. The effects of optical signal-to-noise ratio sensitivity, chromatic dispersion, cross-channel nonlinearity, and transmission distance on the performance of differential 8-ary phase-shift keying (D8PSK), differential phase-shift keying plus three-level amplitude-shift keying (DPSK+3ASK), and dual-carrier differential quaternary phase-shift keying (DC-DQPSK) are evaluated. The performance of coherent dual-polarization quadrature phase-shift keying (DP-QPSK) with block phase estimation and coherent DP-QPSK with digital differential detection are also presented for reference. According to our analysis, all three direct detection modulation formats could transmit a 100-Gb/s signal over several hundred kilometers of a single-mode fiber link. The results also show that DC-DQPSK outperforms D8PSK and DPSK+3ASK, and the performance of DC-DQPSK is comparable to that of coherent DP-QPSK with digital differential detection. The maximum transmission distance of DC-DQPSK is over 1,000 km, which is enough distance for metro applications.
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Design of Hybrid Optical Amplifiers for High Capacity Optical Transmissio
SeungKwanKim,주무정,SunHyokChang,JinSooHan 한국전자통신연구원 2002 ETRI Journal Vol.24 No.2
This paper describes our design of a hybrid amplifier composed of a distributed Raman amplifier and erbium- doped fiber amplifiers for C- and L-bands. We character- ize the distributed Raman amplifier by numerical simula- tion based on the experimentally measured Raman gain coefficient of an ordinary single mode fiber transmission line. In single channel amplification, the crosstalk caused by double Rayleigh scattering was independent of signal input power and simply given as a function of the Raman gain. The double Rayleigh scattering induced power pen- alty was less than 0.1 dB after 1000 km if the on-off Raman gain was below 21 dB. For multiple channel amplification, using commercially available pump laser diodes and fiber components, we determined and optimized the conditions of three-wavelength Raman pumping for an amplification bandwidth of 32 nm for C-band and 34 nm for L-band. Af- ter analyzing the conventional erbium-doped fiber ampli- fier analysis in C-band, we estimated the performance of the hybrid amplifier for long haul optical transmission. Compared with erbium-doped fiber amplifiers, the optical signal-to-noise ratio was calculated to be higher by more than 3 dB in the optical link using the designed hybrid am- plifier.
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HeeSangChung,이현재,주무정,SunHyokChang,HeukPark 한국전자통신연구원 2003 ETRI Journal Vol.25 No.6
This report describes the effect of optical delay on the suppression of the power transient excursion in a combined gain-controlled erbium-doped fiber amplifier with an internal optical feedback loop (OFL). A simple homogeneous model showed that the optical delay caused a phase change in the oscillation of the surviving and laser channels, which resulted in a reduction of the overall power transient excursion. In addition to the reduction, a real system with a 1528.7-nm OFL shifted the oscillation upward or downward according to channel removal or addition, whereas another one with a 1560.9-nm OFL did not. This different transient behavior reflected a control-wavelength dependence on optical automatic gain control, where spectral-hole burning dominated over relaxation oscillation for 1528.7 nm, and vice versa for 1560.9 nm.
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