元代 鹽法의 成立과 運用에 관한 考察 : 원대 염법의 성립과 운용에 관한 고찰

한영근 부산대학교 사학회 1999 釜大史學 Vol.23 No.-

Transmission Characteristics of Multiply-cascaded Phase-shifted Long-period Fiber Gratings

한영근 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.57 No.61

The transmission characteristics of multiply-cascaded phase-shifted long-period fiber gratings (LPFGs) are investigated theoretically and experimentally. By including the phase-shift in the middle of a LPFG, an optical filter, such as a bandpass filter can be realized. A wavelength shift of the passband occurs as the amount of phase shift in the middle of a LPFG changes. The bandwidth of the passband in the phase-shifted LPFG is changed by increasing the number of phase-shifted LPFGs. When two -shifted LPFGs with different lengths of gratings are cascaded in series, the bandwidths of the rejection band and the passband can be controlled by using the pristine characteristics of two gratings. We also analyze the transmission characteristics of multiplycascaded phase-shifted LPFGs theoretically by using a transfer matrix method.

A Development Methodology for Heterarchical Control of Flexible Manufacturing Systems

한영근 한국경영과학회 1995 한국경영과학회 학술대회논문집 Vol.- No.1(2)

This paper presents a methodology for development of a heterarchical control system in Flexible Manufacturing Systems (FMS) environment. A Petri net based model is applied for development of control software. A real-time scheduling methodology for the heterarchical system is also developed and it is used as a software entity in the overall architecture. The partition of generic and specific modules in control software development is emphasized. The control system performs its control tasks in two stages; (1) generation of generic control code and distribution of them to each controller entity prior to system execution; (2) generation of specific control code according to job arrival and its process plan. The control software and the scheduling algorithm are evaluated by a simulation program.

Tunable Multiwavelength Erbium-doped Fiber Laser Based on an In-line Mach Zehnder Interferometer

한영근 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.57 No.61

A tunable multiwavelength erbium-doped fiber laser based on an in-line Mach Zehnder interferometer is proposed and experimentally demonstrated. The in-line Mach Zehnder interferometer is realized by using cascaded long-period fiber gratings. The long-period fiber gratings can couple the guided core mode to several cladding modes. If two identical long-period fiber gratings are concatenated, an interference pattern can be generated, which results from an interaction of the core and the cladding modes in the second long-period fiber grating. Therefore, a simple multichannel filter based on an in-line Mach Zehnder interferometer can be realized. The wavelength spacing of the proposed multichannel filter is controlled by the number of long-period fiber gratings. We apply the proposed multichannel fiber to the generation of a multiwavelength erbium-doped fiber laser with a tunability on the order of the wavelength spacing. An erbium-doped fiber amplifier is implemented as a gain medium. The gain competition of erbium ions is suppressed by soaking the erbium-doped fiber in liquid nitrogen. The power fluctuation of the proposed multiwavelength fiber laser is measured to be less than 0.5 dB. A high-quality multiwavelength output with a high extinction ratio of more than 40 dB is achieved. The wavelength spacing of the proposed multiwavelength fiber laser is controlled by increasing the number of long-period fiber gratings. The wavelength spacing is changed from 0.8 nm to 1.6 nm discretely.

Korean Blue Community를 찾아서...

한영근 한국청소년시설환경학회 2016 한국청소년시설환경학회 학술대회 Vol.2016 No.05

Thermally Tunable Multiwavelength Raman Fiber Laser Based on a Novel In-line Interferometer

한영근 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.58 No.42

A thermally tunable multiwavelength Raman fiber laser based on a simple in-line interferometer is investigated. A novel in-line interferometer is realized by using a single long-period fiber grating incorporating a core misalignment method. Cladding modes from the guided core mode are excited in the splicing point between two optical fibers when two core regions are misaligned. By removing an external buffer coating layer in the fiber, the cladding modes can be propagated and recoupled to the core mode at a long-period fiber grating. Since the long-period fiber grating couples the core mode to the cladding modes, the interaction between the core mode and the cladding modes induces an interference pattern, which realizes a multichannel filter. Since the transmission characteristics of the long-period fiber grating are effectively controlled by changing the applied temperature, a thermally tunable multichannel filter based on the proposed in-line interferometer can be obtained. When the proposed multichannel filter is inserted within the ring cavity of a Raman fiber laser, a multiwavelength Raman fiber laser is realized. A high extinction ratio of more than 40 dB is achieved. The output power is stable, and the power fluctuation is measured to be less than 0.7 dB, and the proposed multiwavelength Raman laser has a high thermal tunablity of -0.48 nm/℃.

320-Gbit/s (32 Chs × 10 Gbit/s) WDM Transmission Over 1.7 km of a Bending-Insensitive Holey Fiber with a Small Bending Diameter

한영근 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.3

We experimentally investigated a 320-Gbit/s (32 Chs × 10 Gbit/s) wavelength division multiplexed (WDM) transmission over 1.7 km of a bending-insensitive holey fiber with 10 turns of 5 mm in bending diameter. The holey fiber with a germanium-doped core and with one layer of air holes in the silica cladding region was fabricated by using the thermal expanding technique. The fabricated holey fiber had a low bending loss of less than 0.04 dB for a bending diameter of 5 mm. The 320-Gbit/s optical source consisted of 32 WDM channels with 100-GHz channel spacing in the C-band. After transmission over 1.7 km of the proposed bending-insensitive holey fiber, error free operation of all 32 channels at a bit error rate of 10-9 was achieved.

All-FBG-Based Switchable Dual Wavelength Erbium-Doped Fiber Laser with High Wavelength Tunability

한영근 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.4

A simple technique for a dual wavelength-switchable erbium-doped fiber laser with high tunability of the lasing wavelength based on fiber Bragg gratings is proposed and experimentally demonstrated by using both control of the linear cavity loss and homogeneous gain broadening of an erbium-doped fiber (EDF). The oscillating wavelength switching of the proposed fiber laser is successfully realized by modulating the acousto-optic modulator driven by a radio-frequency (RF) signal. The wavelength spacing and the lasing wavelength of the proposed wavelength-switchable laser can be controlled by using the tension and the compression strain corresponding to the bending direction. The proposed wavelength-switchable fiber laser has many advantages over previous techniques, such as a high extinction ratio of more than ∽40 dB, a high tunability of ∽7.2 nm/m.

Triple-wavelength Switchable Multiwavelength Erbium-doped Fiber Laser Based on a Highly Nonlinear Photonic Crystal Fiber

한영근 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.56 No.4

We propose and experimentally investigate a novel scheme for a triple-wavelength switchable multiwavelength erbium-doped fiber laser based on a highly nonlinear photonic crystal fiber incorporating a multiply-phase-shifted fiber Bragg grating. A nonlinear optical loop mirror based on a highly nonlinear photonic crystal fiber is exploited to suppress the homogeneous line broadening of an erbium-doped fiber amplifier and to provide the triple lasing wavelength switchability. A multiplyphase-shifted fiber Bragg grating with three channels, depending on the number of phase-shifted segments, is implemented to establish a multichannel filter and to generate the multiwavelength output. A high-quality multiwavelength output with a high extinction ratio of 45 dB and a high output flatness of 0.3 dB is realized. The switching performance to provide lasing-wavelength selectivity can be realized by using a nonlinear polarization rotation based on a nonlinear optical loop mirror. The lasing wavelength can be switched individually by controlling both the polarization controller within the nonlinear optical loop mirror and the cavity loss. The proposed multiwavelength fiber laser can be operated in the single-, dual-, and triple-lasing wavelength states. Based on the bending technique, the lasing wavelength of the proposed multiwavelength erbium-doped fiber laser can be readily controlled, and its tunability was measured to be 7.2 nm/m−1.

Dependence of the Transmission Characteristics of Versatile D-shaped Fibers on Temperature and Ambient Index Changes for Different Input Polarization States

한영근,Oh-Jang Kwon,김현주 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.56 No.4

We investigate the dependence of the transmission characteristics of versatile D-shaped fibers on temperature and ambient index changes for different input polarization states. Various D-shaped fibers with different surface structures, such as a thin layer and periodic surface gratings, were fabricated by coating a photoresister (PR) on the surface of a D-shaped fiber. For the D-shaped fiber with a thin layer, a TE mode has a higher temperature sensitivity than a TM mode because the TE mode has a continuous tangential electric field at the boundary between the surface of the D-shaped fiber and the thin layer whereas the TM mode has a discontinuous electric field at the boundary between the two regions. For the D-shaped fiber with periodic surface gratings, the TE mode also has a higher temperature sensitivity than the TM mode. The temperature sensitivity of the D-shaped fiber with periodic surface gratings is higher than that with a thin layer because of the large surface area of the PR affected by the external temperature change. We also measure the sensitivities of two D-shaped fibers to the ambient index change. For the D-shaped fiber with a thin layer or periodic surface gratings, the sensitivity of the TM mode to the ambient index change is higher than that of the TE mode because the evanescent field of the TM mode is more sensitive to the external index change than that of the TE mode.