• Current Optics and Photonics
• /
• 제6권3호
• /
• pp.297-303
• /
• 2022

Multiple fiber Bragg gratings (FBGs) have been proposed and demonstrated for gas-flow measurements in a flow channel, using the temperature-difference method. This sensor consists of two FBG temperature sensors and two coil heaters. Coil heaters are used to heat the FBGs. The flow rate of the gas can be obtained by monitoring the difference in the Bragg-wavelength shifts of the two FBGs, which has features that exclude the effect of temperature fluctuations. In this study, experiments are conducted to measure the wavelength shift based on the flow rate, and to evaluate the gas-flow rate in a gas tube. Experimental results show that the sensor has a linear characteristic over a flow-rate range from 0 to 25 ℓ/min. The measured sensitivity of the sensor is 3.2 pm/(ℓ/min) at a coil current of 120 mA.

• Current Optics and Photonics
• /
• 제4권3호
• /
• pp.186-192
• /
• 2020

This paper describes a real-time monitoring system in Ethernet passive optical networks (EPON) that uses burst-mode fiber Bragg grating (FBG) optical sensors. The FBG interrogation unit in the optical line terminal (OLT) transmits the monitoring wavelength to optical network units (ONUs). The FBG sensor unit in each ONU returns a burst-mode monitoring signal to the OLT. As the system applies time division multiple access (TDMA), a uniform Bragg wavelength can be used to monitor the EPON system. The FBG interrogation unit analyzes the received burst-mode monitoring signals and outputs fault information on the ONU branches in EPON. The simulation results show the effectiveness of the proposed monitoring system based on TDMA. In addition, we compared the proposed TDMA-based monitoring system with a WDMA-based monitoring system.

• 비파괴검사학회지
• /
• 제36권6호
• /
• pp.460-465
• /
• 2016

배관 구조물은 긴 길이를 가지며, 일정한 거리에 위치한 고정부에 설치되거나, 지중에 매설된다. 따라서 자중 또는 지반의 움직임으로 변형과 처짐이 발생하기 쉽다. 이러한 배관의 건전성 평가에는 형상 감시 기법이 매우 유용할 수 있다. 광섬유 브래그 격자 센서 (fiber Bragg grating, FBG)는 다중화의 장점이 있어 배관과 같이 긴 길이를 가지는 구조물의 여러 지점에서 변형률 측정에 매우 유용하다. 본 연구에서는 배관의 건전성 평가를 위하여 변형률 기반의 형상추정기법을 제안하였다. 제안된 기법의 유용성을 확인하기 위하여 실험을 통한 검증을 수행하였다. 실험 결과 제안된 FBG를 이용한 형상추정기법이 시험편의 변형에 따라 유사한 형상을 표현할 수 있음을 확인하였다. 또한, 형상추정기법을 통해 도출된 처짐량이 실제 배관에 가해진 처짐과 동일하게 계산됨을 확인하였다.

• Archives of Plastic Surgery
• /
• 제37권3호
• /
• pp.233-238
• /
• 2010

Purpose: As the use of soft tissue fillers becomes more popular, complications such as foreign body granuloma (FBG) are increasing. We report 120 cases of facial FBG and review the available literatures. Methods: 120 patients of facial FBG in our clinic from Mar. 2003 to Feb. 2008 were complied and analyzed. A retrospective chart review was done and patient satisfaction was evaluated with a questionnaire using 5 score scale. Patients with severe inflammation sign or bizarre deformity underwent surgical excision and those with minimal symptoms or a history of hyaluronic acid injection received injection therapy using hyaluronidase. Results: 100 females and 20 males were observed. The average age was 43.7 years (from 16 to 74). 84 patients received surgical therapy and 36, injection therapy. Deformity of facial contour, foreign body sensation and inflammation sign were the three main chief complaints. 84 patients did not know what the injection materials were. The known materials are as follows: collagen, hyaluronic acid, silicone oil, paraffin. 92 cases were performed by unlicensed practitioners, 29 by physicians. Anatomical site most frequently affected by the foreign body granuloma was the cheek (25.8%), followed by forehead (19.2%), lips (15.8%), nose (9.2%), mentum (8.3%), eyelid and eyebrow (4.3%) and temple (0.8%). In 21 patients (17.5%), FBGs were found on multiple sites. Patients with inflammation sign got the highest satisfaction ($3.19{\pm}0.73$) (p=0.001) among 3 chief complaints. And patient satisfaction was statistically higher in surgical therapy group ($3.43{\pm}0.72$) than in injection therapy group ($2.97{\pm}0.88$) (p=0.003). Conclusion: We suggest that it may be beneficial to tailor the type of treatment for FBG relying on wound state and patient's chief complaints. In surgical therapy, resolute approach is necessary to correct facial deformity definitely and to minimize inflammation. Injection therapy could be another option for those with minimal symptoms or a history of hyaluronic acid injection. To prevent foreign body granuloma, not only plastic surgeons but also other physicians should inject soft tissue fillers with great caution and we should warn the public of disastrous consequences associated with illegal medical practice.