• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.1
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• pp.54-62
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• 1999

In this paper, we investigated the signal-to-noise ratio improvement in a differential detector, which is a function of the optical noise coupling ratio and the differential gain ratio. A differential detector consists of two photodiodes and a differential amplifier. The differential detector reduced the noise component and improved the signal-to-noise ratio by about 20 dB when the differential gain ratio equals to the optical noise coupling ratio. The differential detector is very effective in removing the environmental optical noise or interference from an adjacent optical channel. This method is also effective when the noise wavelength is similar to the signal.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.5
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• pp.1606-1623
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• 2015

Optical switching will be applied in datacenter networks because electronic switching is costly and power-consuming. In this paper, considering the ring-based interconnection using optical switching in the core of a datacenter, we study the home circuit (HC) construction for the labeled optical burst switching with home circuit (LOBS-HC), a new paradigm trying to share wavelengths among the HCs from the same source. In particular, aiming to construct HCs dynamically and properly, a scheme named optimal path matching and symmetric HC matching (OPM-SHM) is proposed. The main idea of OPM-SHM is to dynamically construct HCs by sharing wavelength(s) not only among the same-source HCs but also with symmetric HCs which have different sources other than the original LOBS-HC features. The simulation results demonstrate that OPM-SHM achieves better performance than some other methods in terms of burst loss rate and wavelength utilization of physical links. More specially, it maintains good load balancing for the datacenter network using an LOBS-HC ring. In addition, due to the symmetric feature of SHM, the proposed scheme can decrease the upper bound of the average hop count of the routing paths to half of the ring size.

• Journal of the Korean Society for Precision Engineering
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• v.31 no.6
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• pp.469-475
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• 2014

The roll to roll (RTR) imprint process is an integrated imprinting process where steps ranging from assignment of a function to a flexible rolled substrate to rewinding of the same substrate in a roll are performed. RTR imprint is a green, low-cost technology without limitations. In RTR imprint, it is important to manufacture the mold precisely and maintain uniform process condition. To this, process conditions have to include precision tension control, optimization of process parameters. We introduced RTR imprint to fabricate planar lightwave circuit (PLC) device for communication, by new schematic design and process optimization, we fabricated successfully optical device. The fabricated optical device showed the optical performance which was satisfied to meet international standard.

• Journal of the Microelectronics and Packaging Society
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• v.20 no.3
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• pp.19-22
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• 2013

Recently, high speed transmission and large information demand have been increased. Also, researches of integrated optical device for large production and high-efficient planar lightwave circuit (PLC) have been increased. In this paper, integrated optical alignment is proposed which makes passive alignment between optical device and optical fiber possible. The integrated optical device consists of splitter structures which have one input and two outputs. The proposed integrated structure was fabricated by roll-to-roll (RTR) processing method. This method enables to manufacture continuously and the processing time can be shortened. Optical property of the fabricated optical device showed 3.9 dB insertion loss and 0.2 dB optical uniformity using the light source with 1550 nm wavelength.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.16 no.10
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• pp.934-940
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• 1991

A modified quantizing method is introduced to teach single layer learning algorithm, which is implemented optically. The proposed optical system consists of input masks, holographic diffraction grating. LCD and CCD camera. The 2 dimensional interconnections between input neurons and output neurons are realized using holographic phase grating, which is fabricated for equal intensity distribution of diffraction orders. The two gray levels of LCD act as binary weights for each interconnection. The weights are compensated according to the learning algorithm in which the amount of weights to be compensated is determined by comparing the output patterns with target patterns. The learning process is iterated until the predetermined conditions are satisfied. Optical experiments are performed for two learning rates, 0.5 and 0.9 and the experimental results show that the proposed system is useful for optical neural networks.

• Korean Journal of Optics and Photonics
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• v.23 no.1
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• pp.12-16
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• 2012

In the paper, we fabricated a Ni master with $45^{\circ}$-mirror structures for flexible waveguide fabrication. The flexible waveguide films with embedded $45^{\circ}$-angled mirrors at the waveguide ends were successfully fabricated using a UV-imprint process. Next, in order to enhance the reflectivity of the mirrors, Ni(3 nm)-Au(200 nm) bilayers were evaporated on the $45^{\circ}$-angled facets through a locally opened thin mask using an electron beam evaporator. We measured propagation loss, bending loss, mirror loss and bending reliability of the fabricated waveguide.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.30B no.10
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• pp.95-104
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• 1993

IPA(interpattern association) model is a method of feature extraction using a neural network. Even in the case that the reference patterns are simuklar to one another, this model can recover the reference patterns effectively. However, when the pattern whose feature pixels are lost is used as input, this model can not guarantee perfect recovery of the reference pattern. It is proposed a improved interpattern association(IPA) model for the feature extraction using neural network. The improved IPA model that combines the first interconnection weight matrix of the IPA model with the second additional weight matrix is proposed here to overcome the recovery problem of the original IPA model. The results of computer simulation and optical experiment are advanced.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.6
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• pp.75-81
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• 1995

InGaAsP/InP uncooled LDs emitting at 1.3$\mu$m wavelength are of interest for several application of fiber-to-the-home, optical interconnection, long-haul high-bit-rate optical transmission systems, etc. The strain compensated PBH-MQW-LD employing 1.4% compressive strained well (${\lambda}=1.3{\mu}m$) and 0.7% tensile strained barrier (${\lambda}=1.12{\mu}m$) layers grown by low pressure metallicorganic vapor phase epitaxy was found to be low threshold current and stable temperature characteristics. The average threshold current of 5.6mA and average slope efficiency of 0.27mW/mA at room temperature were obtained for uncoated uncooled-LD.

• 한국정보통신설비학회:학술대회논문집
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• 2005.08a
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• pp.166-169
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• 2005

고속 데이터 전송을 함에 있어서 레이저 다이오드(LD)를 이용한 광접속 시스템은 최근 중요한 화두가 되고 있다. LD에 의하여 변조된 광신호는 광자와 캐리어의 동역학적 특성에 영향을 받으며, 이와 같은 LD의 동작 특성을 위해하기 위해서는 율방정식(Rate Equation)을 분석해야만 한다. 본 논문에서는 유한차분법(FDM)을 이용하여 율방정식을 분석하기 위한 모델을 제시하였으며, 이때 주입되는 전류부분에 디지털 혹은 아날로그 신호를 인가함으로써, 광접속 시스템에서 LD의 대역폭, SFDR (Spurious Free Dynamic Rage) 그리고 비선형 특성을 분석하였다.

• Proceedings of the KIEE Conference
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• 1994.11a
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• pp.385-387
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• 1994

Optical interconnections are more attractive than electronic interconnections because of their higher speed, freedom from planar constraints, immunity to electromagnetic interference effects and higher interconnection capacity. Volume hologram is one of the best way to implement optical interconnections. Diffraction efficiency and crosstalk effect are very important things for ensuring independent interconnections. Recently, a general systematic method that can handle a large number of superposed volume gratings in anisotropic host material is presented. In this study for numerical analysis of diffraction, above method is programmed in general form near Bragg angle. Diffraction orders for variation of grating strength are determined by comparing with the coupled-mode method. The effects of parameter variation are considered. Parameters include vertical and azimuthal incident angle, wavelength and interaction length. Diffraction analyses are also performed for intra-mode and inter-mode diffractions.