• The Journal of the Acoustical Society of Korea
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• v.21 no.1E
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• pp.25-30
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• 2002

We report on the development of a fiber optic hydrophone consists of a sensing Michelson interferometer and a compensating Mach-Zehnder interferometer for optical path length compensation. The double interferometer configuration has the following advantages: the hydrophone can be made more small; a laser source with a relatively short coherence length can be used; and the compensating interferometer can be located near the signal processing electronics, far away from the sensing interferometer and noise introduced by reference arm can be greatly reduced. The performance of the hydrophone is evaluated experimentally by immersing the sensing interferometer in a water tank to detect underwater acoustic signals generated by an acoustic wave projector. Experimental results show that over the frequency range of 1 to 4 kHz, the hydrophone has an almost flat response with an average normalized sensitivity of -302 dB re 1/ μ Pa.

• International Journal of Internet, Broadcasting and Communication
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• v.14 no.3
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• pp.63-68
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• 2022

Two wavelength reconfigurable optical nodes are designed. One for 20km or shorter link length, and the other for up to 60km link length. While the first one requires no dispersion compensation, the latter needs dispersion compensation fiber included in the node, which requires additional optical amplifier to compensate the insertion loss of DCF. We calculate all the optical path losses in both cases using the typical value of optical components in the market to see the feasibility of the designed optical node. The minimum received power in the node is calculated to be -21.5dBm without DCF and -12.5dBm with DCF, respectively. These received powers are above the receiver sensitivity both for OC-48 and OC-192 according to the previous work.

• Journal of Advanced Navigation Technology
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• v.7 no.1
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• pp.14-21
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• 2003

We investigated the optimum pump light power compensating distorted WDM signal due to both chromatic dispersion and self phase modulation (SPM). The considered system is $3{\times}40$ Gbps intensity modulation direct detection (IM/DD) WDM transmission system with path-averaged intensity approximation (PAIA) mid-span spectral inversion (MSSI) as compensation method. This system have highly nonlinear dispersion shifted fiber (HNL-DSF) as nonlinear medium of optical phase conjugator (OPC) in the mid-way of total transmission line. We confirmed that HNL-DSF is an useful nonlinear medium in OPC for wideband WDM transmission, and the excellent compensation is obtained when the pump light power of HNL-DSF OPC was selected to equalize the conjugated light power into the second half fiber section with the input WDM signal light power depending on total transmission length. By this approach, it is verified the possibility to realize a long-haul high capacities WDM system by using PAIA MSSI compensation method, which have HNL-DSF OPC with optimal pump light power depending on transmission length.

• Korean Journal of Optics and Photonics
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• v.29 no.1
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• pp.1-6
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• 2018

In this study, ray-tracing software was used to calculate the optical path length of an optical system. Using the optical path length, the optical phase, group delay (GD), group delay dispersion (GDD), and third-order dispersion (TOD) of the optical system were obtained. Pulse compressors using a prism pair or grating pair were designed to compensate the GDD of a real optical system for a femtosecond fiber laser. Also, a pulse stretcher using a grating pair with lenses or mirrors was designed. The results of this study can be used to calculate the dispersion of an optical system and optimize the performance of an ultrashort pulse laser optical system.

• Journal of Sensor Science and Technology
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• v.30 no.1
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• pp.36-41
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• 2021

The motivation of this paper is to easily analyze the properties of nondispersive infrared gas sensor that has more than two different optical path length and to suggest the criterion and definition of infrared light absorbance in order to minimize the measurement errors. With the output voltage ratios and the normalized derivatives of infrared ray (IR) absorbance, when the normalized derivatives of IR absorbance decreases from 0.28 to 0.10, the lower and higher limits of errors were decreased from -5.62% and 2.39% to -4.27% and 2.78%. When the normalized derivatives of IR absorbance were 0.10, the output voltage could be partitioned into two regions with one exponential equation and the temperature compensation error was less than 5%.

• Journal of Advanced Navigation Technology
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• v.7 no.2
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• pp.128-134
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• 2003

In this paper, we investigated the degree of compensation for WDM channel signal distortion due to chromatic dispersion, self phase modulation (SPM) and cross phase modulation (XPM) as a function of transmission length using mid-span spectral inversion (MSSI) compensation method. The considered system is $3{\times}40$ Gbps intensity modulation direct detection (IM/DD) WDM transmission system. This system has highly nonlinear dispersion shifted fiber (HNL-DSF) as a nonlinear medium in optical phase conjugator (OPC). We confirmed that the transmission length is more increased by applying MSSI to distorted signal due to chromatic dispersion, SPM and XPM as dispersion coefficient of fiber becomes higher. And the compensation degree of distorted WDM channels due to chromatic dispersion, SPM and XPM becomes better stable as dispersion coefficient of fiber becomes higher.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.3A
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• pp.168-177
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• 2005

In this paper, we numerically investigated the optimum pump light power resulting best compensation of pulse distortion due to both chromatic dispersion and self phase modulation (SPM) in long-haul 3×40 Gbps wavelength division multiplexing (WDM) systems. We used mid-span spectral inversion (MSSI) method with path-averaged intensity approximation (PAIA) as compensation approach, which have highly nonlinear dispersion shifted fiber (HNL-DSF) as nonlinear medium of optical phase conjugator (OPC) in the mid-way of total transmission line. We confirmed that HNL-DSF is an useful nonlinear medium in OPC for wideband WDM transmission, and in order to achieve the excellent compensation the pump light power is selected to equal the conjugated light power into the latter half fiber section with the input light power of WDM channel depending on total transmission length. Also we confirmed that compensation degree of WDM channel with small conversion efficiency is improved by using pump light power increasing power conversion ratio upper than 1.

• Journal of the Korean Institute of Gas
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• v.15 no.4
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• pp.51-55
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• 2011

This paper describes the temperature compensation algorithm using thermopile detector for nondispersive infrared methane gas sensor. From the output voltage of thermistor that is attached onto the infrared detector, the ambient temperature was extracted. The effects of temperatures on the properties of sensor module (the characteristics of narrow bandpass filter, optical cavity and infrared lamp, and gas absorption coefficient times optical path length) have been introduced in order to implement the temperature compensation algorithm. Even though the measurement error of developed sensor module was in the range of $\pm$ 1,500 ppm, after programming the temperature compensation algorithm, the developed sensor module shows a high accuracy less than +180 ppm error within $20^{\circ}C$ temperature variation.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.8
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• pp.845-854
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• 2003

In this paper, the characteristics of compensation for WDM channel signal distortion due to both chromatic dispersion and Ken effect in 1,000 km 200 Gbps(5${\times}$40 Gbps) WDM systems was investigated. The WDM system has a path-averaged intensity approximation(PAIA) mid-span spectral inversion(MSSI) as a compensation method. This system has a highly nonlinear dispersion shifted fiber(HNL-DSF) optical phase conjugator(OPC) in the mid-way of transmission line. In order to evaluate the degree of compensation, 1 dB eye opening penalty(EOP), bit error rate(BER) characteristics and power penalty of 10$\^$-9/ BER are used. It is confirmed that HNL-DSF is an useful nonlinear medium in OPC fur wideband WDM system with PAIA MSSI and that the optimal compensation for WDM channel distortion is achieved by the selection of pump light power of OPC, which equalize the conjugated light power into the second half fiber section with the input WDM signal light power depending on total transmission length, dispersion coefficient of fiber, OPC pump light wavelength, conversion efficiency of WDM channel in OPC.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.5A
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• pp.473-483
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• 2004

In this paper, we numerically investigated the optimum pump light power best compensating for pulse distortion due to both chromatic dispersion and self phase modulation (SPM) as a function of channel input power in 8 channel ${\times}$ 40 Gbps wavelength division multiplexing (WDM systems. Also we investigated the allowable maximum channel input power dependence on modulation format and fiber dispersion coefficient in the various pump light power of OPC. The considered WDM transmission system is based on path-averaged intensity approximation (PAIA) mid-span spectral inversion (MSSI) compensation method, which has highly-nonlinear dispersion shifted fiber (HNL-SDF) as nonlinear medium of optical phase conjugator (OPC) in the mid-way of total transmission line. We confirmed that optimal pump light power of HNL-DSF OPC depend on modulation format, initial channel input power, total transmission length and fiber dispersion. But optimal pump light power of HNL-DSF OPC must be selected to make power conversion ratio to almost unity. And we confirmed that, if we allow a 1 dB eye opening penalty (EOP), the tolerable maximum channel input power is increased by using RZ than NRZ as modulation format when pump light power of HNL-DSF OPC is not optimal value but another values.