• Journal of the Optical Society of Korea
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• v.14 no.4
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• pp.351-356
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• 2010

We investigated the combined effect of fiber chromatic dispersion and self-phase modulation (SPM) in multi-channel subcarrier multiplexed (SCM) optical transmission systems. We theoretically analyzed the transmission characteristics of the SCM signals with the effect of SPM and chromatic dispersion in a single-mode optical fiber by numerical simulations based on the nonlinear Schrodinger equation. The numerical simulation results revealed that the effect of fiber dispersion and SPM could occur independently between subcarrier channels in two-channel SCM systems for small optical modulation index (OMI) and large channel spacing. However, for large OMI, small channel spacing, and large fiber launching power, we found a performance degradation of the two-channel system compared to that of a single-channel system. These parameters are therefore important for the optimization of multi-channel SCM systems applicable to radio over fiber networks.

• Journal of the Optical Society of Korea
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• v.7 no.2
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• pp.97-101
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• 2003

The transmission characteristics of multi-channel long period fiber gratings (LPFGs) in terms of the physical parameters like the separation distance, grating length and number of gratings will be discussed. Their transmission characteristics such as channel spacing, number of channels, loss peak depth, and channel bandwidth can be easily controlled by physical parameters. Based on the experimental results, their applications to optical multiwavelength Raman lasers and optical sensors will be investigated. A multiwavelength Raman fiber ring laser with 9 WDM channels with 100 ㎓ spacing and 19 channels with 50 ㎓ spacing using tunable multi-channel LPFGs will be experimentally demonstrated. The fiber-optic sensing applications with high resolution and sensitivity based on multi-channel LPFGs will be also presented.

• Journal of the Optical Society of Korea
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• v.15 no.2
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• pp.132-139
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• 2011

We investigate theoretically the combined effect of fiber chromatic dispersion and self-phase modulation (SPM) on multi-channel subcarrier multiplexed (SCM) optical transmission systems in terms of the detected RF carrier power and SPM-induced power gain after transmission over single-mode fiber (SMF) links. According to the calculated power gain due to the SPM effect at the transmission distance of P3dB using the detected radio-frequency (RF) carrier power after photo-detection, the power gain is significantly degraded with large optical modulation index (OMI), small SCM channel spacing, and large fiber launching power because of the increased interaction between subcarrier channels. The nonlinear phase shift due to linear and nonlinear fiber characteristics is investigated to explain these results in detail. The numerical simulation results show that the OMI per SCM channel has to be smaller than 10 % for the fiber launching power of 10 dBm to guarantee prevention of SPM-induced power gain degradation below 0.5 dB for the SCM system with the channel spacing of 100 MHz. This result is expected to be utilized for the optical transmission systems using the SCM technology in future radio-over-fiber (RoF) networks.

• Structural Engineering and Mechanics
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• v.77 no.4
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• pp.523-533
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• 2021

The present study investigates the lateral torsional buckling behaviour of pultruded glass fiber reinforced polymer (GFRP) simply supported channel beams subjected to uniform bending about their major axis. A parametric study by varying the sectional geometry and span of channel beams is carried out by using ABAQUS software. The accuracy of the FE models was ensured by verifying them against the available results provided in the literature. The effect of geometric nonlinearity, geometric imperfections, and the dependency of finite element mesh on the lateral torsional buckling were carefully considered in the FE model. Lateral torsional buckling (LTB) strengths obtained from the numerical study were compared with the theoretical LTB strengths obtained based on the Eurocode 3 approach for steel sections. The comparison between the numerical strengths and the design procedure proposed in the literature based on Eurocode 3 approach revealed disagreements. Therefore, a simplified improved design procedure is proposed for the safe design strength prediction of pultruded GFRP channel beams. The proposed equation has been provided that might aid the structural engineers in economically designing the pultruded GFRP channel beams in the future.

• The Journal of the Acoustical Society of Korea
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• v.20 no.7
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• pp.89-93
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• 2001

In recent years Fiber optic hydrophone systems have been the focus of much attention in the sonar world. For sonar arrays, a fiber optic approach offers the major benefit of passive multiplexing of large numbers of hydrophones without underwater electronics. This paper describes recent development work covering array construction, opto-electronics development, hydrohpone design and sea trials. And the development of an interferometric mult-channel fiber optic hydrophone system which uses time division multiplexing capable of driving in excess of 32 channel is described. For this, a 12 channel time division multiplexing array has been constructed, and the performance of this system is demonstrated by sea trial.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.8
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• pp.133-139
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• 1995

In this paper, the frequency separation locking and interval stabilization of 4-channel DFB-LDs have been demonstrated using a fiber Fabry-Perot filter with an free spectral range of 100GHz. Frequency fluctuation and locking range of each channel were appeared to be within 15MHz and over 12GHz, respectively. Back-reflection curve from the fiber Fabry-Perot filter was used for the extraction of an error signal in order to increase the number of accomodable channels and extinction ratio.

• Journal of Electrical Engineering and Technology
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• v.4 no.3
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• pp.405-409
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• 2009

A polarization-independent multiwavelength-switchable fiber filter is proposed based on a polarization beam splitter and fiber coupler, which can function as a polarization-independent transmission or reflection-type interleaving filter. The proposed filter consists of a polarization beam splitter and a Sagnac birefringence loop composed of a 50:50 coupler, high birefringent fibers, and two quarter-wave plates. In the proposed filter, a transmission-type interleaver with a channel isolation > 18 dB or a reflection-type one with a channel isolation of ${\sim}3$ dB, whose channel spacing and switching displacement were 0.8 and 0.4 nm in common, respectively, could be obtained. A channel interleaving operation could be performed by the proper control of waveplates within the Sagnac birefringence loop.

• The Korean Journal of Physiology and Pharmacology
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• v.11 no.5
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• pp.215-219
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• 2007

Small and large conductance $Ca^{2+}$-activated $K^+(SK_{Ca}\;and\;BK_{Ca})$ channels are implicated in the modulation of neuronal excitability. We investigated how changes in peripheral $K_{Ca}$ channel activity affect mechanical sensitivity as well as the afferent fiber type responsible for $K_{Ca}$ channel-induced mechanical sensitivity. Blockade of $SK_{Ca}$ and $BK_{Ca}$ channels induced a sustained decrease of mechanical threshold which was significantly attenuated by topical application of capsaicin onto afferent fiber and intraplantar injection of 1-ethyl-2-benzimidazolinone. NS1619 selectively attenuated the decrease of mechanical threshold induced by charybdotoxin, but not by apamin. Spontaneous flinching and paw thickness were not significantly different after $K_{Ca}$ channel blockade. These results suggest that mechanical sensitivity can be modulated by $K_{Ca}$ channels on capsaicin-sensitive afferent fibers.

• Journal of Advanced Navigation Technology
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• v.11 no.2
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• pp.177-186
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• 2007

In this paper, the optimal position offset of optical phase conjugator (OPC) and the optimal dispersion offsets of fiber sections, which are alternating with the method for the symmetry of optical power and chromatic dispersion with respect to OPC, are numerically investigated as afunction of the WDM channel numbers. The WDM channel numbers are assumed to be 8, 12, 16, 20 and 24. The bit-rate of each channel is assumed to be 40 Gbps for all cases. It is confirmed that the optimal position offset of OPC and optimal dispersion offset of fiber section are gradually increased as the WDM channel numbers are gradually increased. But, the optimal dispersion values of fiber sections per OPC position offset of 1 km are independent on WDM channel numbers, because the optimal position offset of OPC and optimal dispersion offset of fiber section are simultaneously increased as the WDM channel numbers are increased. It is also confirmed that the applying of these optimal parameter values is efficient to WDM system with many channels rather than WDM with small channels.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.6
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• pp.1234-1242
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• 2004

In this paper, the characteristics of compensation for interferenced mid-channel signal by neighbor channels through four-wave mixing (FWM) process dominantly is investigated as a function of channel input power, fiber dispersion coefficient and transmission length in WDM system with equally spaced channels. The compensation method used in this research is mid-span spectral inversion(MSSI). The highly nonlinear dispersion shifted fiber (HNL-DSF) is used as a nonlinear medium of optical phase conjugator (OPC) in order to compensate wideband WDM signals. First, we confirmed that the effect of FWM on channel interference is gradually reduced as fiber dispersion coefficient becomes gradually smaller, independent of signal format. And, we confirmed that RZ is better than NRZ as a modulation format for transmitting high power channel with allowable reception quality. But realization of flexible WDM systems regardless of channel number variation is possible by using NRZ rather than RZ format.