• Journal of Advanced Navigation Technology
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• v.27 no.4
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• pp.457-462
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• 2023

We proposed a flexible link configuration in a system combining mid-span spectral inversion (MSSI) and dispersion management used for long-distance transmission of high-capacity optical signals such as wavelength division multiplexing signals, and examined specific methods to increase chromatic dispersion and nonlinear distortion compensation effects. The dispersion map proposed to increase the flexibility of dispersion-managed link configuration has a 'random-inverse' structure. That is, in the proposed dispersion map, the residual dispersion per span (RDPS) of each fiber span in the first half section up to the optical phase conjugator is randomly distributed, and the RDPS distribution in the second half section reverses the distribution pattern of the first section. Although the proposed dispersion map has a random distribution of RDPS, it was confirmed that the distortion compensation effect is improved due to the fact that the dispersion profile is symmetrical with respect to the optical phase conjugator. In the dispersion map of the 'random-inverse' configuration, it was also confirmed that the compensation effect of the distorted wavelength division multiplexing signal becomes improved when the magnitude of the RDPS allocated to each fiber span is large.

• Journal of Advanced Navigation Technology
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• v.6 no.3
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• pp.223-230
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• 2002

In this paper, we induced that the noise powers and bit error rate of direct detection receiver taking account of ISI (intersymbol interference) in the 2,000 km optical transmission system. And we evaluated the sensitivity in the vrious bit rate system. We verified that the proposed calculation method is applicable to the exact optical system. And we confirmed that the signal distortion due to both chromatic dispersion and nonlinear effects compensated by using of MSSI (Mid-Span Spectral Inversion) method, and yet the sensitivity of a higher bit rate system is reduced, because of the increase of ISI and then the decrease of the average receiving power, compared with a the lower bit rate system.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.8 no.4
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• pp.297-304
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• 1996

The purpose of this study is to observe the applicability of parabolic mild-slope equations allowing relatively large angles of wave propagation based on the use of a Pade approximant or minimax approximation and also the applicability of the models with nonlinearity of diffracted waves in the shadow zone behind coastal structures. To accomplish these objectives, numerical solutions are obtained from the above parabolic models and are compared with the results from Watanabe and Maruyama's(1984) hydraulic model test on the wave field with an impermeable detached breakwater. From this study, it is found that computed wave heights increase for the nonlinear results in comparison to the linear results due to the increased diffraction effect across the geometric shadow boundary. The model with a larger aperture with respect to the principal direction was found to spread laterally to a much greater degree where spreading angle (diffraction effect) is relatively large. which causes a distortion in the overall results due to the error accumulated by the approximation of wave length.

• Journal of Advanced Navigation Technology
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• v.20 no.2
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• pp.161-166
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• 2016

In high capacity and long haul optical communication systems, signal distortion is induced by chromatic dispersion and nonlinear effects of optical fibers. Dispersion management (DM) combining with mid-spans spectral inversion (MSSI) is one of the various techniques for overcoming this drawback. The most simple configuration of DM link is obtained by uniformly distributing the lengths of single mode fiber (SMF) and residual dispersion per span (RDPS) over whole fiber spans consisted of optical link. In this paper, the system performances in the uniformly distributed DM link combined with MSSI are assessed as a function of the number of fiber spans, because the system performances in this configuration are used as the significant performance criterion in other link configurations, such as the artificial distribution or the random distribution of SMF lengths and RDPS.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.9
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• pp.2219-2226
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• 2013

Optical phase conjugation combining with dispersion management (DM) is promising technique to compensate for signal distortion due to group velocity dispersion (GVD) and nonlinear Kerr effects in optical communication systems. However the fixed residual dispersion per span (RDPS) usually used in the optical links with OPC and DM restricts the flexible link configuration. In this paper, OPC links combining DM of the randomly distributed RDPS is proposed for implementing the flexible optical transmission network. It is confirmed that the excellent compensation in the optical links with the randomly distributed RDPS is obtained, limiting the launch power of WDM channels to the relatively low. It is also confirmed that the relatively high launch power WDM channels are effectively transmitted through the optical links with the randomly distributed RDPS of averaged 50 - 100 ps/nm.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.16 no.5
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• pp.152-161
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• 2017

The CBTC(Communication based Train Control) system employed on 2.4GHz ISM band adopt the IEEE802.11.x standard. Therefor communication time delay, distortion and data losses will be produced. To overcome these problems, CPSK(Continuous Phase shift keying) modulated DS/SS(Direct Sequence Spread Spectrum) transmitter with 908MHz carrier frequency is proposed. Through the eye diagram and scatter diagram the performance is analysed. And the phase noise characteristic of the local oscillator is measured about 60dBc/Hz, this means that the phase noise performance is very good compared to the signal. Reference frequency suppression of the 2nd local oscillator is 50dB below compared to the signal. Through the polarities of the complementary signal equally probable, the line spectrum of the output spectrum is eliminated. The nonlinear effects which introduce the spectral spreading or spectral regeneration is reduced remarkably.

• Journal of Advanced Navigation Technology
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• v.22 no.3
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• pp.240-245
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• 2018

A flexible dispersion-managed link configuration is proposed by using single-mode fibers (SMFs) and dispersion-compensating fibers (DCFs) with irregular dispersion coefficients and lengths over all fiber spans for compensating of WDM channels distortion due to the group velocity dispersion and nonlinear effects of optical fibers. The flexibility of link is enabled by artificially distributing of these fibers based on the dispersion coefficients of DCFs in each half transmission section. The simultaneous ascending and descending (AD) distribution of the DCF's coefficients before and after the optical phase conjugator, respectively, best compensates the distorted wavelength division multiplexed signals in the optical link. Therefore, to improve the compensation effect of the distorted WDM channels, AD distribution is needed to choice regardless of fiber lengths and the residual dispersion per span and fiber's dispersion coefficients.

• Journal of Advanced Navigation Technology
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• v.22 no.5
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• pp.462-466
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• 2018

Optical phase conjugation combining with dispersion management (DM) is promising technique to compensate for signal distortion due to chromatic dispersion and nonlinear Kerr effects of single mode fiber (SMF) in optical communication systems. However the fixed SMF length in every fiber spans usually used in the optical links with optical phase conjugator(OPC) and DM restricts the flexible link configuration. The goal of this paper is to investigate the possibility of the flexible configurations of the ultra-high and long-haul optical transmission systems by using the random distribution of SMF length of each fiber spans consisted of the optical link. It is confirmed that the excellent compensation for the distorted wavelength division multiplexing signals in the optical links with the randomly distribution is obtained in case of the shorter averaged SMF length over all fiber spans. It is also confirmed that the control method of net residual dispersion suitable to good compensation is postcompensation and the extent of net residual dispersion(NRD) is -10 ps/nm in DM optical link consisted of fiber spans with the randomly distributed SMF lengths.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.10B
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• pp.855-864
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• 2008

Optical link techniques compensating chromatic dispersion and nonlinear effects, which affect distortion of optical signals, generated in single mode fiber are investigated through computer simulation and design rule of these link techniques is proposed for implementation of wideband and long-haul WDM ($24{\times}40$ Gbps) transmission system. The optical link consist of dispersion management (DM) compensating the cumulated dispersion through total transmission line and optical phase conjugation in middle of total transmission line for compensating distorted signals by frequency inversion. DM schemes considered in this research are lumped DM and inline DM. It is confirmed that eye opening penalty (EOP) of overall WDM channels are more improved than those in WDM transmission systems with only optical phase conjugator (OPC), if DM is additionally applied to these systems. And, design rule in both DM schemes are proposed by using effective residual dispersion range. It is confirmed that inline DM is better than lumped DM in the improving EOP of total WDM channels and in effective residual dispersion range.

• The Transactions of the Korean Institute of Power Electronics
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• v.16 no.6
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• pp.569-576
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• 2011

This paper proposes a new dead time compensation method for a PWM inverter. Recently, PWM inverters are extensively used for industry applications, such as ac motor drives, distributed grid-connected systems and a static synchronous compensator (STATCOM). Nonlinear characteristics of the switch and the inverter dead time cause a current distortion and deterioration of power quality. The dominant harmonics in the output current are the $5^{th}$ and $7^{th}$ harmonics in the stationary frame, and the $6^{th}$ harmonics in the synchronous rotating frame. In this paper, a resonant controller which compensates the $6^{th}$ harmonics in the synchronous rotating frame is proposed. This method does not require any off-line experimental measurements, additional hardware and complicated mathematical computations. Furthermore, the proposed method is easy to implement and does not cause any stability problem.