• Korean Journal of Optics and Photonics
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• v.4 no.3
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• pp.354-358
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• 1993

The temperature distribution inside a zigzag slab laser glass was measured using a Mach-Zehnder interferometer. The temperature difference between the center and the surface of the slab caused the fracture of the slab glass. Two laser glasses were fractured at a temperature difference ${\Delta}T_0$of TEX>$110^{\circ}C$, $62^{\circ}C$ respectively. For the design of high-average power glass laser, it is recommended that the limit of the temperature difference ${\Delta}T_0$ inside the slab glass should be smaller than $50^{\circ}C$ for safe operation.ration.

• Proceedings of the KIEE Conference
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• 2000.11c
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• pp.605-606
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• 2000

본 논문에서는 광섬유 장주기 격자쌍과 두 장주기 격자 사이에 삽입된 어븀 첨가 광섬유를 이용하며, 광섬유 브래그 격자 센서 헤드에 가해지는 동적 스트레인을 측정하기 위한 새로운 고분해능 파장 측정 시스템을 제안하였다. 제안된 측정 시스템에 대한 실험을 통해 제안된 시스템이 기존의 비대칭 마하 젠더 간섭계를 이용한 파장 측정 시스템에 비하여 훨씬 높은 분해능을 갖고, 외부 온도 변화에 대한 변동 또한 훨씬 적어진 것을 보였다.

• Korean Journal of Optics and Photonics
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• v.10 no.3
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• pp.233-236
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• 1999

We have constructed a narrow-linewidth single-longitudinal-mode unidirectional $Er^{3+}$ -doped fiber laser using a fiber Bragg grating incorporated by a three port optical circulator with a compact configuration. Using a conventional delayed self-heterodyne detection technique with Mach-Zehnder interferometer a linewidth of 5 kHz was measured. In a single-longitudinal-mode operation, output power of up to 2.7 mW at 1548 nm were obtained for a launched pump power of 43 mW at 980 nm.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.5
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• pp.956-962
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• 2008

We propose the optical CDMA based audio acoustic sensor using optical fiber sensors which can be used in the bottom of the sea. In the proposed network, we analyzed the performance of noise power. Numerical simulations confirm that the performance can be improved by increasing the measuring time of optical sensors compared with using conventional WDMA method.

• Journal of Advanced Marine Engineering and Technology
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• v.21 no.4
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• pp.437-442
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• 1997

An experimental study was carried out in a channel cavity with square heat surface by visual¬ization equipment with Mach - Zehnder interferometer and laser apparatus. The image processing system consists of one commercial image board slit into a personal computer and 2-dimensional sheet light by Argon-Ion Laser with cylindrical lens and flow picture recording system. Instant simultaneous velocity vectors at whole field were measured by 2-D PIV system which adopted two¬frame grey-level cross correlation algorithm. Heat source was uniform heat flux(o.4W/cm$^2$, , O.8W/cm$^2$, 1.2W/cm$^2$). Obtained result showed various flow patterns such as kinetic energy distribution. Severe unsteady flow fluctuation within the cavity are remarkable and sheared mixing layer phenomena are also found at the region where inlet flow is collided with the counter-clockwise rotating main primary vortex. Photographs of Mach ~ Zehnder are also compared in terms of constant heat flux.

• Korean Journal of Optics and Photonics
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• v.8 no.4
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• pp.333-339
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• 1997

We fabricated a sensor head which consists of spliced different-diameter fiber gratings for discrimination between strain and temperature. Because the fibers were drawn from the same preform, their temperature characteristics were the same but not for strain sensitivities which are inversely proportional to fibers cross-sectional areas. In measurement range of 0-1500$\mu$strain and 20-10$0^{\circ}C$, we could obtain, by using the matrix calculation, the unknown physical quantities within 10% of calculation error compared with the micrometer and thermocouple values. To improve the strain measurement accuracy, we suggest a new, novel method which deploys an unbalanced fiber Mach-Zehnder interferometer. This new signal processing technique converts the strain information to interference signal amplitude variation, temperature-independently. we obtained measurement accuracy nearly 80 times better than that obtainable with the conventional optical spectrum analyzer usage.

• Korean Journal of Optics and Photonics
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• v.10 no.1
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• pp.47-52
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• 1999

This study describes a simple and effective experimental determination of pump-power dependence of refractive indices and dispersions of erbium-doped fibers (EDFs) of various doping concentrations. Systermatical analysis on light-induced change of the refractive indices and dispersion for a signal wavelength range of 1510 nm-1560 nm with a pump of 980 nm wavelength has been made by measuring the pump-induced phase changes of the signal beam in Mach-Zehnder type interferometer, which has an optically pumped EDF and a reference EDF in each of the two arms, respectively. The measured pump-induced refractive indices match well with the theoritically predicted ones. The results show that pump-induced refractivity and dispersion changes of the EDF increase with the increasing pump power and $Er^{3+}$-doping concentration as expected from theory.

• Journal of the Korean Vacuum Society
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• v.20 no.2
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• pp.106-113
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• 2011

We describe a single shot off-axis digital holography based on a Mach-Zehnder interferometic scheme for measuring temperature distribution of a microheater. The proposed scheme has the capability of reconstructing object phase image which is dependent of the temperature distribution in real time. Experimental results shows that there is a moderate linear relationship between the measured phase and temperature in the range of $20^{\circ}C$ to $60^{\circ}C$. We expect that the proposed system can provide a very reliable and fast solution in various surface temperature distribution measurement applications.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.4
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• pp.38-44
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• 2000

In this paper, we have been fabricated λ/2 phase plates lot an optical pick-up using a blue violet laser diode by employing proton exchange and wet etching in LiNbO$_{3}$. Their functions and fabrication processes are described in detail. It is established the optimal fabrication conditions through the experimental results. The device characteristics are measured by the Mach-zender interferometer which is composed of the optical components and 632.8nm He-Ne laser. The measured phase error was ＋5$^{\circ}$~ -6$^{\circ}$(within 3%). This phase plate could be applied an useful device to improve the resolution and the stability of the optical pick-up which has a blue violet laser diode as an optical source.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.6
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• pp.706-715
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• 2012

Electro-optical sigma-delta modulators are the core module of digital receiver to digitize wideband radio-frequency signals directly at an antenna. Electro-optical sigma-delta modulators use a pulsed laser to oversample an input radio-frequency signals at two Mach-Zehnder Interferometer(MZI) and shape the quantization noise using a fiber-lattice accumulator. Decimation filtering is applied to the quantizer output to construct the input signal with high resolution. The jitter affects greatly on reconstructing the original input signal of modulator. This paper analyzes the performance of first order single bit electro-optical sigma-delta modulator in the time domain and the frequency domain. The performance of modulator is analyzed by using asynchronous spectral averaging of the reconstructed signal's spectrum in the frequency domain. The reference value of time jitter is presented by analyzing the performance of jitter effects. This kind of jitter value can be used as a reference value on the design of modulators.