• Title/Summary/Keyword: Free-space optics

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1km Optical fiber transmission and free space characteristics of the PQR laser (PQR 레이저의 1km 광섬유 전송 및 자유공간 특성)

  • 김무성;곽규섭;김준연;김무진;권오대
    • Proceedings of the IEEK Conference
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    • 1999.11a
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    • pp.322-325
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    • 1999
  • We report fiber guiding experiments on the Photonic Quantum Ring(PQR) laser diode. In the 1km transmission measurements, we find that the PQR performs much better than the VCSEL. This suggests that the PQR laser is very promising candidate for LAN-range optical data communications. On the other hand, we have also fabricated 8$\times$8 PQR laser arrays and measured spatial decays for free space properties without using any guiding optics, which showed about 1m distance of spectral angle sensing.

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Optical Interconnection and Clocking Using Planar-Integrated Free-Space Optics

  • Jahns, Jurgen;Gruber, Matthias;Lunitz, Barbara;Stolzle, Markus
    • Journal of the Optical Society of Korea
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    • v.7 no.1
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    • pp.1-6
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    • 2003
  • Integration and miniaturization at the systems level are key requirements for photonics applications. Here, we describe the concept of planar integration of free-space optical systems and its use as an optical interconnection technology. Two specific applications will be considered, a parallel chip-to-chip interconnect and an optical clock distribution network.

Planar integrated optics for implementation of fractional fourier transform (분수차 퓨리에 변환을 위한 평판집적 광학계 구현)

  • 박선택;김필수;오차환;송석호
    • Korean Journal of Optics and Photonics
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    • v.7 no.4
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    • pp.333-340
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    • 1996
  • We have implemented a planar integrated optics for the fractional Fourier transform (FRT) which has recently been developed as a generalized form of the conventional Fourier transform. FRT optical systems provide versatile tools for analyzing signals and designing hardwares, but require high accuracy and stability in the arrangement of optical components because of their shift-variant characteristic. The planar optical FRT setup composed of free-space optical components integrated on a single glass block makes the FRT of 2-dimensional(2-D) input patterns through the 3-D glass-space. Therefore, taking advantage of the compactness, easy alignment and thermal/mechanical stability, the planar optics can provide a useful approach to realizing an optical fractional correlation system in a practical way. In the experiment, we have obtained accurate FRT results by using the planar integrated optics with 4 different fractional orders of 0.25, 0.5, 0.75, and 1.0.

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Accuracy Improvement and Systematic Bias Analysis of Scanning White Light Interferometry for Free-form Surfaces Measurements (자유 곡면 형상 측정을 위한 백색광 주사 간섭계의 정확도 향상 및 시스템 오차 분석)

  • Ghim, Young-Sik;Davies, Angela;Rhee, Hyug-Gyo
    • Journal of the Korean Society for Precision Engineering
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    • v.31 no.7
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    • pp.605-613
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    • 2014
  • Scanning white-light interferometry is an important measurement option for many surfaces. However, serious profile measurement errors can be present when measuring free-form surfaces being highly curved or tilted. When the object surface slope is not zero, the object and reference rays are no longer common path and optical aberrations impact the measurement. Aberrations mainly occur at the beam splitter in the interference objective and from misalignment in the optical system. Both effects distort the white-light interference signal when the surface slope is not zero. In this paper, we describe a modified version of white-light interferometry for eliminating these measurement errors and improving the accuracy of white-light interferometry. Moreover, we report systematic errors that are caused by optical aberrations when the object is not flat, and compare our proposed method with the conventional processing algorithm using the random ball test.

Single Logarithmic Amplification and Deep Learning-based Fixed-threshold On-off Keying Detection for Free-space Optical Communication

  • Qian-Wen Jing;Yan-Qing Hong
    • Current Optics and Photonics
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    • v.8 no.3
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    • pp.239-245
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    • 2024
  • This paper proposes single logarithmic amplification (single-LA) and deep learning (DL)-based fixed-threshold on-off keying (OOK) detection for free-space optical (FSO) communication. Multilevel LAs (MLAs) can be used to mitigate intensity fluctuations in the received OOK signal by their nonlinear gain characteristics; however, it is ineffective in the case of high scintillation, owing to degradation of the OOK signal's extinction ratio. Therefore, a DL technique is applied to realize effective scintillation compensation in single-LA applications. Fully connected (FC) networks and fully connected neural networks (FCNN), which have nonlinear modeling characteristics, are deployed in this work. The performance of the proposed method is evaluated through simulations under various scintillation effects. Simulation results show that the proposed method outperforms the conventional adaptive-threshold-decision, single-LA-based, MLA-based, FC-based, and FCNN-based OOK detection techniques.

Numerical Study on the Link Range of the IM/DD Wireless Optical Communication at 830[nm] Optical Wavelength using Galilean Optics (갈릴리안 광학계를 사용한 IM/DD 광무선통신 시스템에서 830[nm] 광파장에 대한 전송거리 제한 해석)

  • Hong, Kwon-Eui;Ko, Sung-Won;Cho, Jung-Whan
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.25 no.11
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    • pp.123-129
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    • 2011
  • In terrestrial wireless optical communication links, atmospheric effects including turbulence, absorption and scattering have significant impact on the system performance. Based on the analysis of transmission in atmospheric channel concerning 830[nm] wavelength diode laser beam, performance of free space optical (FSO) link utilizing Galilean optics as a laser beam transmitting and receving optics, PIN photodiode as a detecting device. In this paper we designed optical link equation for received optical power and we analyze the atmospheric effects on the signal to noise ratio (SNR) and bit error rate (BER) of an terrestrial FSO system. We show that the possible communication distance for BER=$10^{-9}$ in proposed adverse atmospheric conditions.

Weather-insensitive Optical Free-space Communication Using the Gain-Saturated Optical Fiber Amplifier (이득 포화된 광섬유증폭기를 사용하는 기상에 둔감한 무선광통신)

  • Shin, Kyung-Woon;Hurh, Yoon-Suk;Lee, Sang-Hoon;Lee, Jae-Seung
    • Korean Journal of Optics and Photonics
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    • v.17 no.5
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    • pp.396-400
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    • 2006
  • We present a weather-insensitive optical free-space communication method supporting optical packet channels. It operates optical fiber amplifiers in gain-saturation regions. When the propagation loss gets too high, it decreases the average packet rate, or the average packet length, or both, to increase the optical power level launched into the free-space. As a demonstration, we transmit $8{\times}10$ Gigabit Ethernet channels over a terrestrial distance of 2.4 km. One gain-saturated free-space optical repeater is used at the halfway point.

Link Availability of Terrestrial Free-space Optical Communication Systems in Korea (우리나라 옥외 무선광통신 시스템의 링크 가용성)

  • Mai, Vuong V.;Ha, Dung T.;Kim, Hoon
    • Korean Journal of Optics and Photonics
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    • v.29 no.2
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    • pp.77-84
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    • 2018
  • We analyze the link availability of terrestrial free-space optical (FSO) communication systems in Korea. For this purpose, we utilize several theoretical models to calculate the power losses induced by absorption and scattering in the atmospheric channel, using five-year meteorological data for three major cities in Korea (Seoul, Busan, and Daejeon). Also, we estimate the power variations at the receiver caused by scintillation in the data. Those power losses and variations are used to estimate the availability of FSO links in the three cities. The results show that link availability is estimated to be over 95% in Daejeon for a 3.5-km FSO link, when the transmitter power and receiver diameter are greater than 10 dBm and 7 cm respectively. Slightly worse link availabilities are obtained for Busan and Seoul.

Link Availability of Satellite-to-ground Free-space Optical Communication Systems in South Korea (우리나라 위성-지상 하향 무선 광통신 시스템의 링크 가용성)

  • Kim, Gyuwan;Kim, Daeho;Vuong, V. Mai;Kim, Hoon
    • Korean Journal of Optics and Photonics
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    • v.33 no.3
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    • pp.113-121
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    • 2022
  • We analyze the link availability of satellite-to-ground free-space optical (FSO) communication systems in South Korea. Using ten-year meteorological data for five major cities (Seoul, Busan, Daegu, Daejeon, and Gwangju), we theoretically predict the link availability from the power losses induced by absorption, scattering, aerosols, and scintillation in the atmospheric channel. For accurate but conservative estimation of the link availability determined by cloud cover, we propose a loss model based on the maximum value of cloud droplet concentration. The results show that the link availability ranges from 45% to 70% when a single ground station is placed in a major city in South Korea and a 20-dB link budget is allocated for atmospheric loss. However, the availabilities improve to 90% and 97% when 3- and 5-site diversities are employed, respectively.

Impact of the Gain-saturation Characteristic of Erbium-doped Fiber Amplifiers on Suppression of Atmospheric-turbulence-induced Optical Scintillation in a Terrestrial Free-space Optical Communication System

  • Jeong, Yoo Seok;Kim, Chul Han
    • Current Optics and Photonics
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    • v.5 no.2
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    • pp.141-146
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    • 2021
  • We have evaluated the suppression effect of atmospheric-turbulence-induced optical scintillation in terrestrial free-space optical (FSO) communication systems using a gain-saturated erbium-doped fiber amplifier (EDFA). The variation of EDFA output signal power has been measured with different amounts of gain saturation and modulation indices of the optical input signal. From the measured results, we have found that the peak-to-peak power variation was decreased drastically below 2 kHz of modulation frequency, in both 3-dB and 6-dB gain compression cases. Then, the power spectral density (PSD) of optical scintillation has been calculated with Butterworth-type transfer function. In the calculation, different levels of atmospheric-turbulence-induced optical scintillation have been taken into account with different values of the Butterworth cut-off frequency. Finally, the suppression effect of optical scintillation has been estimated with the measured frequency response of the EDFA and the calculated PSD of the optical scintillation. From our estimated results, the atmospheric-turbulence-induced optical scintillation could be suppressed efficiently, as long as the EDFA were operated in a deeply gain-saturated region.