• Korean Journal of Optics and Photonics
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• v.14 no.6
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• pp.630-635
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• 2003

We propose an encryption method using visual cryptography and virtual phase images. In the encryption process, the original image is shared by virtual images and the decryption key image. We multiply the virtual phase images with each complex image, which has the constant value of its sum after performing the phase modulation of the virtual images and the decryption key. The encryption cards are made by Fourier transforming the multiplied images. It is possible to protect information about the original image because the cards do not have any information from the original image. To reconstruct the original image, all the encryption cards are placed on each path of a Mach-Zehnder interferometer and then the lights passing through them are summed. Since the summed image is inverse Fourier transformed by a Fourier lens, the phase image is multiplied with the decryption key and the output image is obtained in the form of intensity on the CCD plane. Computer simulations show a good performance of the pro-posed optical security system.

• Proceedings of the KIEE Conference
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• 1999.07d
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• pp.1599-1601
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• 1999

The characteristics of ultrasonic signal in insulation oil were investigated by optical fiber sensor(OFS) utilizing Mach-Zehnder interferometer. For checking the response properties of OFS ultrasonic signal was generated by function generator in various kinds of insulation oil. The attenuation of ultrasonic signal linearly increased with the increase of viscosity of insulation oil in log scale. Discharging signal was produced by neele-sphere electrode system. Intensity of discharging signal was plotted in terms of cumulative $y^2$ and the intensity of discharging signal in new oil was little bigger than that in serviced one.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.3 no.2
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• pp.123-130
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• 1991

The mixed convection heat transfer from vertical inline plates has been studied numerically by the finite difference method and experimentally with Mach-Zehnder interferometer. The dimensionless spacing, $s/L_1$, the relative length, $L_2/L_1$ and the dimensionless temperature ratio, ${\Phi}_2/{\Phi}_1$ are varied parametically. The lower plate mean Nusselt numbers show same values as $s/L_1$, ${\Phi}_2/{\Phi}_1$ and $L_2/L_1$ increase. The upper plate mean Nusselt numbers increase as $s/L_1$ and ${\Phi}_2/{\Phi}_1$ increase, but $L_2/L_1$ decreases. The upper plate mean Nusselt number is higher than the lower plate mean Nusselt for $s/L_1$ 1.8 at Re=100, $Gr=10^4$, Pr=0.71, $L_2/L_1=0.5$ and ${\Phi}_2/{\Phi}_1=1.0$. A comparison between the experimental and numerical results show good agreement.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.34S no.5
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• pp.15-24
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• 1997

We propose a tunable add/drop filter in a form of an all-fiber mach-zehnder interferometer iwth one bragg grating at each arm. This device can be tuned by inducing a strain in the bragg grating. We also theoretically analyze the outut characteristics of the tunable add/drop filter. As a result of simulation, we know that the proposed tunable add/drop filter works well. When 2*10$^{-3}$ of strain is induced, the reflected spectrum shifts about 3nm. And its reflected spectral width is about 0.3nm. In this case roughly 5 channels can be tuned, assuming the channel spacing is 0.3nm. When the pathlengths of the both arms are not the same, the transmissivities at the add and output ports and the reflectivity at the tap port varies sinusoidally with the pthlength difference. To maintain the transmissivities above 90% in the wavelength tuning range of 20nm the pathlength difference less than 16.mu.m is required.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.1
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• pp.79-83
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• 1998

We analyzed dynamic-strain perturbations applied to a fiber Bragg grating. The fiber Mach-Zehnder interferometer was used, and by analyzing the interference signal wecould obtain the frequency and relative amplitude information of the dynamic-perturbation. The minimum detectable dynamic-strain using the system was ~9.5 nstrain RMS/.root.(Hz) at 500 Hz. Also we proposed and demonstrated a new method which uses a temperature-discriminating dual-trating sensor head. With the method, we could measure the dynamic -strain as well as static-static-strain even for the case in which the optical pathe difference modulation was applied.

• Proceedings of the KIEE Conference
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• 1998.11c
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• pp.922-924
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• 1998

In this paper, an optical fiber sensor(OF sensor) utilizing the principal of Mach-Zehnder interferometer were proposed to detect the partial discharge signals in insulating oil. At first the AC breakdown signals were detected to check the response of the OF sensor. The detected signals from OF sensor was consistent with that from current probe. After the response checking, simultaneous measurements and continuous recording were made of electrical and the OF sensor signals from partial discharge(PD) produced by IEC(b) electrode system immersed in insulating oil. The continuous recording made it possible to extract basic quantities of PD from the OF sensor signals, such as pulse phase and pulse amplitude distribution. Through the signal analysis, the absolute peaks of the OF sensor PD signal was found to be increased with the amplitude of electrical signals, and these results mean that there is a strong correlation between OF sensor and electrical PD signals. It was demonstrated that the OF sensor in this research had a possibility to detect the PD signals in power apparatus.

• Journal of the Optical Society of Korea
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• v.15 no.3
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• pp.244-251
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• 2011

We propose a new 2-step phase-shifting digital holographic optical encryption technique and analyze tolerance error for this cipher system. 2-step phase-shifting digital holograms are acquired by moving the PZT mirror with phase step of 0 or ${\pi}$/2 in the reference beam path of the Mach-Zehnder type interferometer. Digital hologram with the encrypted information is Fourier transform hologram and is recorded on CCD camera with 256 gray-level quantized intensities. The decryption performance of binary bit data and image data is analyzed by considering error factors. One of the most important errors is quantization error in detecting the digital hologram intensity on CCD. The more the number of quantization error pixels and the variation of gray-level increase, the more the number of error bits increases for decryption. Computer experiments show the results to be carried out encryption and decryption with the proposed method and the graph to analyze the tolerance of the quantization error in the system.

• Journal of the Optical Society of Korea
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• v.18 no.6
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• pp.639-645
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• 2014

In this paper, the scheme of a single module for simultaneous operation of all-optical computing circuits, namely half adder and half subtractor, are realized using semiconductor optical amplifier (SOA) based logic gates. Optical XOR gate by employing a SOA based Mach-Zehnder interferometer (MZI) configuration is used to get the sum and difference outputs. A carry signal is generated using a SOA-four wave mixing (FWM) based AND gate, whereas, the borrow is generated by employing the SOA-cross gain modulation (XGM) effect. The obtained results confirm the feasibility of our configuration by proving the good level of quality factor i.e. ~5.5, 9.95 and 12.51 for sum/difference, carry and borrow, respectively at 0 dBm of input power.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.539-544
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• 2001

The holographic measurement techniques can be applied to various industrial fields such as automobile, airplane, construction, electronics, medical, mechanics and physics. The visualization of fluids is very important in aerodynamics, heat transfer and stress analysis. There are classically optical methods such as shadowgraph, schlieren method, and Mach-Zehnder interferometry for visualizing the fluid flow phenomena. But, it is difficult to understand the continuous state of fluids well in those methods. In this study, the real-time holographic interferometer with high-speed camera is applied to the flow visualization. In addition, collimated laser beam and rotating wedge are used for recording and formation of carrier fringes, respectively.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.7
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• pp.109-116
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• 1998

In this work was produced and analyzed a z-cut Ti:LiNbO$_{3}$ optical waveguide which applies for various optical devices.A waveguide channel with a thickness 8 .mu.m and a length 66,000.mu.m and a mach-zehnder interferometer type waveguide were fabricated at a diffusion temperature 1050.deg. C for 6-8hours in a wet $O_{2}$ environment. The resulting Ti:LiNbO$_{3}$ optical waveguide was measured to have a Ti-strip thickness of 950.angs. and low loss. Surfaces and cross-sections of a fabricated waveguide were analysed. The mode pattern anaysis revealed that the waveguide showed a single mode at a 1550nm wavelength. The effective dimension of the waveguide was calculated by measuring a gaussian profile; Wx=10.95.mu. and Wy=9.14.mu.m. a propagation loss, of 0.50dB/cm for a TM mode and 0.45dB/cm for a TE mode, was low enough to be accepatable for optical devices.