• Composites Research
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• v.16 no.2
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• pp.41-47
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• 2003

This paper is concerned with the performance evaluation and comparison analysis fur several kinds of LIPCA (Lightweight Piezo-Composite Actuator) device system. LIPCA device system is composed of a piezoelectric ceramic layer and fiber reinforced light composite layers, typically a PZT ceramic layer was sandwiched by a top fiber layer with low CTE (coefficient of thermal expansion) and base layers with high CTE. To investigate the effect of lay-up structure of the LIPCA on the actuating performance, four kinds of actuator with different lay-up stacking sequence were designed, manufactured, and tested. The performance of each actuator was evaluated using an actuator test system consisted of an actuator supporting jig, a high voltage actuating power supplier, and a non-contact laser measuring system. From the comparison of the performance of the LIPCA prototypes, it was found that the actuator with higher coefficient of unimorph actuator can generate larger actuating displacement.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.12B
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• pp.1236-1243
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• 2010

The perimeter defense system was created and its characteristics were evaluated. It was designed to utilize the fiber sensing device, namely OTDR(Optical Time Domain Reflectometer) which has been used for the maintenance of the optical communication network. An OTDR was constituted by a pulse laser with the nature of 1310nm, +15dBm for the observation of 400 meter optical fence. The high-speed 32-bit processor(S3C2440) has applied to MPU(Main Processor Unit) which helps to improve the performance of OTDR algorithms. Consequently, the maximum error was 0.84 meter on the performance test of the 10km monitoring and the pass criteria of ${\pm}1m$ satisfied in all the sections. The alarm delay time was under 3 sec after detecting the disorder. For the case of secondary trespassing after primary trespassing, the optical switch was installed in OTDR to monitor the secondary trespassing and to measure the multi-point detection. Therefore, this paper shows that the detections of secondary trespassing and multi-point is possible by means of optical switch.

• Korean Journal of Optics and Photonics
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• v.4 no.4
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• pp.420-427
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• 1993

Dielectric thin film mirrors are embedded in multimode and single-mode fibers by a fusion splicing technique. The fibers with $45{\circ}$ angled embedded mirrors serve as ultra-compact directional couplers with low excess optical loss of 0.2 dB for multimode and 0.5 dB for single mode at 1.3 ${\mu}m$ and excellent mechanical properties. The reflectance is wavelength dependent and strongly polarization depencient. Far-field scans of the reflected output power measured with a white-light source show a pattern which is almost circularly symmetric with aspect ratio of 1.09 at 5% of the peak power. The splitting ratio in a multimode coupler measured with a diode laser source is much less dependent on input coupling conditions than in conventional fused biconical-taper couplers, indicating that these couplers are less susceptible to modal noise occuring in optical fiber communication systems. Spectral properties of multilayer internal mirrors normal to the fiber axis have been investigated experimentally, and a matrix analysis has been used to explain the results.

• Korean Journal of Optics and Photonics
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• v.22 no.1
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• pp.5-9
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• 2011

There are technical difficulties in measuring the numerical apertures of multi-mode gradient-index plastic optical fibers (GI-POFs) due to their strong speckle noise originating from dopants, non-uniformity of gradient-index profile, and multi-mode interference. Therefore, we propose a new method of obtaining the numerical aperture by controlling the size of the incident laser beam and measuring the numerical aperture of GI-POF. The results show that we can get a value for the numerical aperture of GI-POF very similar to that measured by the conventional method. We can also obtain the optimum launching condition of input beam and maximum coupling efficiency.

• Journal of The Institute of Information and Telecommunication Facilities Engineering
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• v.3 no.2
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• pp.51-60
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• 2004

In this paper, 8-channel multiplexer with 100GHz channel spacing is fabricated. The 8-channel multiplexer is fabricated by connecting three cascaded Mach Zehnder Interferometer (MZI) of optical fiber type, and each interferometer has the wavelength interval of 100GHz, 200GHz and 400GHz, respectively. furthermore, to acquire uniform insertion loss, it is fabricated by using Wavelength Flatten Coupler (WFC) in which the variation of insertion loss is low. Especially, the variation of wavelength interval in the output is explicitly simulated as a function of optical path difference, and the wavelength coupling process along with cascaded connection is discussed. $CO_2$ laser to adjust precisely the wavelength. In summary, The prototype composed by eight cascaded MZI has an insertion loss of 2.1dB, the bandwidth of 0.8nm at 5.5dB point, and channel crosstalk of 25dB Furthermore, the loss dependent on polarization is measured as 0.06dB.

• Composites Research
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• v.35 no.2
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• pp.53-60
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• 2022

This study uses Diglycidyl ether of terephthalylidene-bis-(4-amino-3-methylphenol) (DGETAM), an amine hardener 4,4'-diaminodiphenylethane (DDE) and cationic catalyst N-benzylpyrazinium hexafluoroantimonate (BPH) to make epoxy film. For analysis, ¹H_NMR and FT-IR were used to verify proper synthesis, and the liquid crystallinity of DGETAM was checked using Differntial Scanning Calorimetry and Polarized Optical Microscopy. Thermal conductivity of the sample was measured using Laser Flash Apparatus. Thermal stability as well as thermal conductivity is important when used as a packaging material. Activated energy is the energy needed to generate a response, which can be used to estimate the energy required to maintain physical properties. It was obtained using the Arrhenius equation based on the data measured by isothermal decomposition using Thermogravimetric Analysis. Measurement of the thermal conductivity of epoxy films showed higher thermal conductivity when DDE was used, and it was found that thermal conductivity had an effect on thermal stability, given that it represented an activation energy similar to a film with BPH upon 5% decomposition.

• Journal of Chest Surgery
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• v.30 no.12
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• pp.1237-1241
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• 1997

Tracheal stenosis is a difficult disease entity to manage. Laser ablation is one effective treatment for treacheal stenosis and can be utilized if tracheal reconstructive surgery is impossible. Potassium titanyl phosphate laser, transmitted via flexible quartz fiber, can be precisely manipulated through flexible bronchoscope under local anesthesia. We treated 7 patients with trach al and broncheal lesion under local anesthesia with KTP laser from January 1995 to July 1996. The patients included three males and four females. The age of patients ranged from 22 to 66 years with a mean of 43.7 years The etiology of tracheal stenosis in patients was stenosis after tracheostomy(3 cases), prolong inturbation in cases of sepsis(1 cases), and the recurrence of lung cancer within endobronchial lesion(2 cases). In the cases of tracheal stenosis treated with laser ablation, there were 2 cases of recurrence of stenosis at the anastomosis site after the operation, 3 cases of stenosis at tracheostomy site, and 2 cases of local recurrence of lung cancer. The site of the tracheal stenosis was the balloon site of the tracheostomy tube(3-4cm inferior to the tracheostomy site, 2-3cm superior to the carina) and the anastomosis site that were narrowed to less than 5mm(4 cases). For the stenosis lesion in the endobronchial area, there were 2 patients with a lesion at the anterior wa l, 1 patient with a lesion at the posterior wall, 2 patients with circumferential stenosis. Laser ablation time was 25.4 $\pm$5.9min and used energy was 1768 $\pm$365J. We have used KTP laser via (lexible bronchoscope without major complications. Adjuvant radiation therapy may prevent fibroblast proliferation which leads to restenosis. In three patients of restenosis after laser ablation, adjuvant irradiation started within 4 hours after laser ablation, and the radiation doses were 1500cGy given in five fraction. In patients with adjuvant radiation therapy, stenosis has not recurred

• Journal of the Korean Society for Nondestructive Testing
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• v.27 no.4
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• pp.299-304
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• 2007

There are to be some cracks on the material degradation part or the stress concentration parts of the main members, which carry on over-loads, of structures. Because these cracks can be used to evaluate the structural health status, it is important to monitor the crack growth for maintaining the structural safety. In this study, the fiber Bragg grating sensor with a drop ball was developed as a sensor for crack growth detection of an existing crack. The crack growth detection sensor was constructed with three parts: a probe part, a wavelength controling light source and receiver part, and an impact part. The probe part was just formed with a fiber Bragg grating optical fiber The wavelength controling light source part was composed of a current supplying circuit, a DFB laser diode, and a TEC controling circuit for wavelength control. Also, the impact part was just implemented by dropping a steel ball. The performance of this sensor was confirmed by the experiments of the crack detection with an aluminum plate having one existing crack. According to these experiments, the difference of the sensor signal outputs was correlated with the crack length. So, it was confirmed that this sensor could be applied to monitor the crack growth.

• Fibers and Polymers
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• v.4 no.2
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• pp.71-76
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• 2003

We evaluated the seam characteristics with finishing, seaming and sealing processes and seam Puckering behavior of the breathable waterproof fabrics with laser scan. There were differences in 99% significant level between the seamed fabric and the sealed fabric. Seam breakage was initiated with the breakage of sewing thread, so the seam strength after seaming was almost uniform. The sewn seam strength and elongation increased with sealing process in all finishing methods. Pucker grade of laminating type was generally much higher than that of the coating type. We confirmed that wave length and amplitude have more important meaning than the number of weave in the breathable waterproof fabrics. The puckering in breathable waterproof fabrics is mainly occurred by inherent and feeding pucker. The former if due to the insertion of sewing thread and the littler is caused by differential feeding when two pieces of fabric are fed into the gap between a press foot and needle plate.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.46 no.8
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• pp.12-17
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• 2009

We have implement어 a bust mode optical transmitter using digital temperature compensation architecture with a microprocessor. Instead of previous analog real time technique, we used digital sampling and holding technique for the temperature compensation in order to get stable high speed data transmission of the laser diode. This digital temperature compensation technique should be complemented the previous analog method with accuracy and effectiveness in the over Gb/s transmitting application.