• Journal of Sensor Science and Technology
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• v.29 no.6
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• pp.412-419
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• 2020

In this study, a PID control method for sweeping automatic linearization of a wavelength swept laser is proposed. First, the closedloop transfer function embodying the PID control is derived. Through the simulation of the function, K_p = 0.022, K_i = 0.008, K_d = 0.002 were obtained as the best PID coefficients for fast linear sweeping. The performance test using the PID coefficients showed that linear sweeping was held up well with a 98.7% decrement in nonlinearity after the 10th feedback, and 45 nm sweeping range, 1 kHz sweeping frequency, and 8.8 mW average optical power were obtained. The equipment consists of a fiber Bragg grating array, an optical-electronic conversion circuit, and a LabVIEW FPGA program. Every 5s, automatic feedback and PID control generate a new compensated waveform and produce a better linear sweeping than before. Compared with nonlinear sweeping, linear sweeping can reduce the cumbersome and time-consuming recalibration processes and produce more accurate measurement results.

• Current Optics and Photonics
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• v.7 no.2
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• pp.166-175
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• 2023

We theoretically analyze and experimentally demonstrate a polarization-diversified four-channel optical demultiplexer (DeMUX) comprising a hybrid mode conversion-type polarization splitter rotator (PSR) and delayed Mach-Zehnder interferometer optical DeMUX for use in coarse wavelength division multiplexing (CWDM)-based optical interconnect applications. The Si wire-based device fabricated by a complementary metal-oxide semiconductor-compatible process exhibited nearly the same filter spectral response irrespective of the input polarization state under the PSR. The device had an extremely low insertion loss of <1.0 dB, polarization-dependent loss of <1.0 dB, and interchannel imbalance of <0.5 dB, suppressing unwanted wavelength and polarization crosstalk from neighboring channels of <-20 dB at each peak transmission channel grid.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.4B
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• pp.351-360
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• 2003

All-optical network provede unlimited for bandwidth, the very low bit error rate, and the transparency to IP. Optical networks promise to be the next generation networks that can meet the higher bandwidth demands. However, the number of wavelengths is often not large enough to help a large amount of nodes. The blocking by wavelength contention can be reduced by wavelength conversion, which can't perfectly resolve all situations. Because of that, a lot of groups have proposed unique wavelength assingment algorithms and protocols. Most schemes don't support the priority concepts. This paper describes the unique priority scheme based on the throughput. In this paper, we apply our priority scheme to SWAP(Simple Wavelength Assignment Protocol) and show the performance of the proposed priority scheme. Our proposed priority scheme can be a better solution to solve an important problem about the blocking by wavelength contention into WDM optical networks.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.51 no.1
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• pp.15-21
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• 2002

We investigated effects of electrical, physical, and chemical parameters on energy transfer, NO conversion, and light emission in the dielectric barrier discharge (DBD) process. As gap distance between electrodes increased, discharge onset voltage increased. However, as gap distance between electrodes increased, electric field which initiates discharge showed approximately the same value, 30kV/cm. The discharge onset voltage of the coarse surface electrode was lower than that of the smooth surface electrode. And, energy transfer was slightly enhanced in the coarse electrode condition. However, NO conversion rate decreased with the coarse surface electrode because more uniform discharge can be obtained on the smooth surface electrode. The NO conversion rate increased with decreasing the initial concentration, so the DBD process is more feasible in the lower concentration condition. The variation of gas residence time tested at the same energy density in the experiment did not affect on the NO conversion. The result shows that the NO conversion rate mainly depends on the energy density. The DBD process is able to adjust on plasma-photocatalyst process because it emits the short wavelength light in the range of ultraviolet. The intensity of light emission increased with the increase of the energy transfer to the reactor and the gas flow rate.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.8 s.350
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• pp.1-14
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• 2006

Multi-constraint QoS routing has been seen as crucial network property in the next generation optical Internet based on DWDM Networks. This paper proposes a new QoS routing algorithm based on flooding method, called bounded flooding routing (BFR) algorithm which can meet multi-constraint QoS requirements. Primarily, the BFR algorithm tries to reduce network overhead by accomplishing bounded-flooding to meet QoS requirements, and improve blocking probability and wavelength utilization. Also, as one effort to improve routing performance, we introduce a new concept, ripple count, which does not need any link-state information and computational process. For extensive analysis and simulation study, as a critical concern, in DWDM-based networks we deploy limited wavelength conversion capability within DWDM nodes. And the simulation results demonstrate that the BFR algorithm is superior to other predominant routing algorithms (both original flooding method and source-directed methods) in terms of blocking probability, wavelength channels required and overhead.

• Korean Journal of Optics and Photonics
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• v.14 no.4
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• pp.454-459
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• 2003

We report the first demonstration of 10 Gb/s wavelength conversion in a Mach-Zehnder interferometric wavelength converter monolithically integrated with a loss-coupled DFB probe source. The integrated device is fabricated using a BRS (buried ridge stripe) structure with an undoped InP clad layer on the top of a passive waveguide to reduce high propagation loss. The device exhibited a static extinction ratio of 11 dB. Good performance at 10 Gb/s is obtained with an extinction ratio of 7 dB and a power penalty of 2.8 dB at a 10$^{-9}$ bit error rate.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.118.1-118.1
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• 2011

The dye-sensitized solar cell (DSSC) is a device for the conversion of visible light into electricity, based on the sensitization of wide bandgap semiconductors. The performance of the cell mainly depends on a dye used as sensitizer. The absorption spectrum of the dye and the anchorage of the dye to the surface of TiO2 are important parameters determining the efficiency of the cell. Generally, transition metal coordination compounds(ruthenium polypyridyl complexes) are used as the effective sensitizers, due to their intense charge-transfer absorption in the whole visible range and highly efficient metal-to ligand charge transfer. However, ruthenium polypyridyl complexes contain a heavy metal, which is undesirable from point of view of the environmental aspects. Moreover, the process to synthesize the complexes is complicated and costly. Alternatively, organic dyes can be used for the same purpose with an acceptable efficiency. The advantages of organic dyes include their availability and low cost. We designed and synthesized a series of organic sensitizers containing long wavelength absorption-chromophores for the dye sensitized solar cell. The DSSC composed of Blue-chromophores for the sensitization absorbed long wavelength region which is different also applied into the dye-cocktail (mixing) system. The photovoltaic property of DSSCs organic long wavelength absorption-chromophores were measured and evaluated by comparison with that of individual chromophores.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.39 no.1
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• pp.58-66
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• 2002

Acousto-optical wavelength tunable optical filters in LiNbO$_3$ have been demonstrated using taperd directional weighted coupling acoustic waveguides and Ti double diffusion technique. Conversion efficiency in excess of 61%, 86% and sidelobe intensity of -14.29㏈, -14.99㏈ were measured at a wavelength of 1551.1nm RF frequency of 173.58MHz and RF power of 35㎽ for both TE and TM input polarizations, respectivelv. A spectral width of ~l.8nm and linear tuning late of 8.6nm/MHz were demonstrated. A 2.82$mutextrm{s}$ switching time has been measured. With two channels with 2.5nmseparation, channel cross-talk was lower than -l4㏈ for single wavelength filtering due to sidelobe.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.8
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• pp.1883-1892
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• 1998

This paper considers the efficient design of routing path and wavelength assignment asignment in the sigle-hop WDM optical transport networks. The connecton demands between node-pairs are given and a connection must be made by only one lightpath. It is assumed that no wavelength conversion is allowed and the physical topology of the network is given. This paper proposes a method to find the routes of lightpaths and assign wavelengths to the routes, which minimizes the number of total wavelength to satisfy all connection demands. We establish a new optimization model that finds the minimum number of wavelengths. A heuristic algorithm with polynomial iterations is developed for the problem. The algorithm is implemented and applied to the netowrks with real problem size. The results of the application are compared with the commericial optimization solver, GAMS/OSL and Wauters & Demeester [8].

• Journal of the Korea Society of Computer and Information
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• v.10 no.5 s.37
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• pp.123-132
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• 2005

In this Paper, we present an improvement of switch node for wavelength multiplex optical network. Currently because of quick increase of internet traffic a big network capacity is demanded. Wavelength multiplex optical network Provides the data transfer of high speed and the transparent characteristic of the data. Therefore optic network configuration is the most powerful technology in the future. It will be able to control the massive traffic from the optical network in order to transmit the multimedia information of very many quantify. Consequently the node where the traffic control is Possible, is demanded. The optical switch node which manages efficiently the multiple wavelength was Proposed. This switch is composed of a optical switch module for switching and a wavelength converter module for wavelength conversion. It will be able to compose the switch fabric without optical/electro or electro/optical conversion using optical MEMS(Micro Electro Mechanical Switches) module. Finally, we present the good test result regarding the operational qualify of the switch fabric and the performance of optical signal from the switch node. The proposed switch node of the optic network will be able to control the massive traffic with all optical.