• Journal of Broadcast Engineering
• /
• v.22 no.5
• /
• pp.665-670
• /
• 2017

In this paper, we propose an implementation technology for an active attenuator with the maximum attenuation of -110dBm in the frequency band of 50MHz to 2,15GHz. It provides USB interface to connect to PC providing GUI that sets signal frequency and attenuation step of minimum 1dB. As it attenuates the input signal level down to -110dBm, circuit and equipment design technologies are applied to control both internal and external electro-magnetic noises.. Through the performance test, it is assured that it attenuates input signal level down to -110dBm for the input signal levels of -10 to -30dBm.

• Korean Journal of Optics and Photonics
• /
• v.14 no.1
• /
• pp.12-16
• /
• 2003

This paper presents a compensation method for a temperature-dependent gain tilt in L-band erbium-doped fiber amplifier using a voltage-controlled attenuator. The gain tilts in the L-band of 1570-1605 nm due to a temperature change have negative slopes, whereas they have positive slopes for the increasing optical input powers in a saturation region. The proposed method utilizes these opposite gain variations to compensate for the gain tilt over a wide range of temperature. While applying forty channels with a channel spacing of 100 GHz in the L-band and changing the ambient temperature from 0 to $50^{\circ}C$, the compensation method maintained the gain deviation within 1 dB.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.15 no.5
• /
• pp.3079-3085
• /
• 2014

This paper suggests a power level controllable frequency up-converter which is designed and fabricated using both the filtering technology consisted with only passive devices and a multi-level digital attenuator. The suggested frequency up-converter simultaneously realizes the low power consumption and the low cost model. Because of the possibility for controlling power levels, it is possible to use the suggested frequency up-converter for wide spectral range. According to the experimental results, the average gain value of 0.75dB is obtained for the bandwidth of 160MHz at the center frequency of 1,200MHz. Especially, it is confirmed that the power level can be controlled from 10 to -21.5dBm through the digital attenuator.

• Korean Journal of Optics and Photonics
• /
• v.29 no.1
• /
• pp.28-31
• /
• 2018

In this paper, we have proposed and demonstrated a variable optical attenuator (VOA) incorporating a dual-fiber collimator and a bimetallic actuator. The optical attenuation between input and output single-mode fibers was tuned by tilting the angle of a reflection mirror fixed on the bimetal. The bimetal was heated or cooled by a thermoelectric cooler (TEC) and then moved the reflection mirror, due to bending and unreeling. The desired optical attenuation can be obtained through adjusting the electrical input into the TEC. The fabricated device showed 0.5 dB of insertion loss, 0.2 dB of maximum polarization-dependent loss, and 40 dB of dynamic range. The response time was measured to be about 5 s.

• Journal of Ocean Engineering and Technology
• /
• v.36 no.2
• /
• pp.132-142
• /
• 2022

We investigate the performance of multi-body wave energy converters (WECs). This investigation considers multiple scattering of water waves by the buoys of a WEC under the generalized mode approach. Predominantly, the effect of a WEC's configuration on its energy extraction is studied in this research. First, single-row terminator and single-column attenuator arrays of vertical cylinders have been studied. The performance of these attenuator arrays shows that the wall effect induced by the periodic buoys influences the wave propagation and energy extraction in these WECs. Further studies show that a single-row terminator array of vertical cylinders performs better than the corresponding single-column attenuator array. Subsequently, multi-row terminator arrays of vertical cylinders are investigated by conducting a parametric study. This parametric study shows that the hydrodynamic property of three resonance phenomena makes energy extraction efficiency drop down, and the magnitude of energy extracted oscillates between the resonance points in these WECs. Finally, a 4×8 terminator array of vertical cylinders is studied to determine the effect of various d_x (x-directional distance between adjacent rows) within this WEC on its performance. In particular, this study enforces at least two equal d_x values within the 4×8 terminator array of vertical cylinders. It shows that a small value of this d_x leads to better energy extraction efficiency in some of these various d_x arrays than that of a corresponding regular array with the same d_x.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.29 no.5A
• /
• pp.566-573
• /
• 2004

A variable optical attenuator with a bending-sensitive fiber (BSF) that can be used in optical networks is developed. The proposed BSF consists of inner core, outer core, center dip and cladding. The proposed BSF is also very sensitive to mechanical perturbation, such as bending and pressure, making the light propagating in the BSF easily controlled and attenuated. The fabricated fiber-type variable optical attenuator using the proposed BSF (VOAFB) consisted of the BSF in a rectangular rubber ring with a fixed bend radius (BR) in a steady state. The variable optical attenuator using the proposed BSF (VOAFB) was able to attenuate the optical power by more than about -38㏈ with the gradient -88.4［㏈$.$$cm^{-1}$ /］ at (1540∼1560nm) based m adjusting the mechanical pressure applied to the upper surface of the rectangular rubber ring with the bent BSF. According to the experimental results when using the proposed VOAFB, the optical power was easily controlled by adjusting mechanical pressure and produced an insertion loss of 0.68㏈, polarization loss of 0.5㏈, and return loss of less than -60㏈.

• The Journal of Korean Society for Radiation Therapy
• /
• v.1 no.1
• /
• pp.43-46
• /
• 1985

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.26 no.2
• /
• pp.44-50
• /
• 2012

When the fiber Bragg gratings are embedded in a fiber-optic Sagnac loop for measuring temperature or strain, it is difficult to separate the Bragg wavelengths. The transmitted light is mixed with the reflected Bragg wavelengths in the photo-detector, working as noises. To suppress the noises, we placed the FBG sensors and a fiber-optic attenuator at asymmetric positions in the loop. With the arrangement the reflected light became much bigger than the transmitted light, enabling the separation of the reflected Bragg wavelengths with almost the same signal-to-noise ratio of the FBG sensors outside the loop.

• Journal of Satellite, Information and Communications
• /
• v.3 no.1
• /
• pp.1-7
• /
• 2008

This Paper studied the design and measured results of a flight model for Ku-Band Linearized Channel Amplifier (LCAMP) for communication satellite onboard system. All MMICs, i.e. Variable Gain Amplifier (VGA), Variable Voltage Attenuator (VVA) with analog/digital attenuator, Branch line Hybrid Coupler and Detector for Pre-distorter are fabricated using Thin-Film Hybrid process. The performance of the fabricated module is verified through Radio Frequency circuit simulations and electrical function test in space environment for flight model at 12.25 to 12.75 GHz.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1997.10a
• /
• pp.273-276
• /
• 1997

Seeing is an intelligent act. Retina is the most important part among the components of eye which is comprised of iris, pupil, lens, optic disk, and so forth. Because retina acts like a photo receiver to detect light from every object, if damaged, animals have a severe problem to live along with themselves and sometimes they lose their sight. In the ophthalmology, doctors use special instrument to see exact retina image of object and operate the surgery by rotating focus control knob. In this study, a basic test is done to achieve the auto focus control instrument. Specially made sledge and attenuator are installed on the optic bed to change the distance and laser power between the first reflective mirror and the second one. Control panel which is compiled by Visual C t t to control stepping motors ,laser power and photodiode are implemented with ADA-board.