• Title/Summary/Keyword: Optical frequency conversion

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Demonstration of Mobile Fronthaul Test Bed Based on RoF Technology Supporting Two Frequency Assignments and 2 × 2 MIMO Antennas

  • Cho, Seung-Hyun;Han, Changyo;Chung, Hwan Seok;Lee, Jong Hyun
    • ETRI Journal
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    • v.37 no.6
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    • pp.1055-1064
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    • 2015
  • We demonstrate a next-generation high-capacity mobile fronthaul based on radio over fiber (RoF) technology, which links between a digital unit and a radio unit supporting two frequency assignments and $2{\times}2$ multiple input, multiple output antennas. To confirm the technical feasibility of a mobile fronthaul, we experimentally investigate its down- and uplink end-to-end performances including the optical and radio frequency (RF) signal path. Frequency-dependent performance deviations, error vector magnitude variations, overall system performance variations caused by optical to electrical conversion, and intermediate frequency to RF conversions are examined. Experimental verifications on multiple LTE uplink signals are performed for the first time. We also demonstrate several commercial mobile Internet services, YouTube video streaming, and file transfers using off-the-shelf mobile devices, through a mobile fronthaul based on RoF.

Periodically Poled BaTiO3: An Excellent Crystal for Terahertz Wave Generation by Cascaded Difference-frequency Generation

  • Li, Zhongyang;Yuan, Bin;Wang, Silei;Wang, Mengtao;Bing, Pibin
    • Current Optics and Photonics
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    • v.2 no.2
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    • pp.179-184
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    • 2018
  • Terahertz (THz) wave generation by periodically poled $BaTiO_3$ (PPBT) with a quasi-phase-matching (QPM) scheme based on cascaded difference-frequency generation (DFG) is theoretically analyzed. The cascaded DFG processes comprise cascaded Stokes and anti-Stokes processes. The calculated results indicate that the cascaded Stokes processes are stronger than the cascaded anti-Stokes processes. Compared to a noncascaded Stokes process, THz intensities from $20^{th}$-order cascaded Stokes processes increase by a factor of 30. THz waves with a maximum intensity of $0.37MW/mm^2$ can be generated by $20^{th}$-order cascaded DFG processes when the optical intensity is $10MW/mm^2$, corresponding to a quantum conversion efficiency of 1033%. The high quantum conversion efficiency of 1033% exceeds the Manley-Rowe limit, which indicates that PPBT is an excellent crystal for THz wave generation via cascaded DFG.

Single-photon Detection at 1.5 ㎛ Telecommunication Wavelengths Using a Frequency up-conversion Detector (주파수 상향변환 검출기를 이용한 1.5 ㎛ 통신파장대역의 단일광자 측정)

  • Kim, Heon-Oh;Youn, Chun-Ju;Cho, Seok-Beom;Kim, Yong-Soo
    • Korean Journal of Optics and Photonics
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    • v.22 no.5
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    • pp.223-229
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    • 2011
  • We present a low jitter frequency up-conversion detector based on quasi-phase matched sum frequency generation in a periodically poled $LiNbO_3$ waveguide for efficient single-photon detection at 1.5 ${\mu}m$ telecommunication wavelengths. The maximum detection efficiency and the noise count rate using the pump power of 300 mW and the pump wavelength of 974 nm are about 7% and 480 kHz, respectively. We also characterize the timing jitter of the frequency up-conversion detector by analyzing the time distribution of the detection outputs for photons generated through a picosecond pump pulsed spontaneous parametric downconversion. The minimum timing jitter was measured to be about 39.1 ps. Coincidence measurement with a narrow time window for pulsed up-conversion photons can eliminate the unwanted noise counts and maximize signal to noise ratio.

Terahertz Generation Based on Cascaded Difference Frequency Generation with Periodically-poled KTiOPO4

  • Li, Zhongyang;Wang, Silei;Wang, Mengtao;Wang, Weishu
    • Current Optics and Photonics
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    • v.1 no.2
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    • pp.138-142
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    • 2017
  • Terahertz (THz) generation by periodically-poled $KTiOPO_4$ (PPKTP) with a quasi-phase-matching scheme based on cascaded difference frequency generation (DFG) processes is theoretically analyzed. The cascaded Stokes interaction processes and the cascaded anti-Stokes interaction processes are investigated from coupled wave equations. THz intensities and quantum conversion efficiency are calculated. Compared with non-cascaded DFG processes, THz intensities from 10-order cascaded DFG processes are increased to 5.53. The quantum conversion efficiency of 479.4% in cascaded processes, which exceeds the Manley-Rowe limit, can be realized.

Parallel 3-dimensional optical interconnections using liquid crystal devices for B-ISDN electronic switching systems

  • Jeon, Ho-In;Cho, Doo-Jin
    • Journal of the Optical Society of Korea
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    • v.1 no.1
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    • pp.52-59
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    • 1997
  • In this paper, we propose a system design for a parallel3-dimensional optical interconnection network utilizing variable grating mode liquid crystal devices (VGM LCD's) which are optical transducers capable of performing intensity-to-spatial-frequency conversion. The proposed system performs real-time, reconfigurable, but blocking and nonbroadcasting 3-dimensional optical interconnections. The operating principles of the 3-D optical interconnection network are described, and some of the fundamental limitations are addressed. The system presented in this paper can be directly used as a configuration of switching elements for the 2-D optical perfect-shuffle dynamic interconnection network, as well as for a B-ISDN photonic switching system.

Radio-on-Fiber 액세스시스템 기술

  • Park, Jong Dae;Nam, Sang Sik;Park, Gwon Cheol
    • The Magazine of the IEIE
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    • v.30 no.3
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    • pp.295-295
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    • 2003
  • The advantages of using analogue optical networks for delivering radio signals from a central location to many remote antenna sites have been recognized. In a telecommnications context, radio signals may be for fixed radio access, cordless or mobile networks, but the same principles apply. By making use of the high bandwidth, low loss characteristics of optical fiber, all high frequency and signal processing functions can be performed centrally and signals can then be transported over the optical network directly at the carrier frequency. The remote sites then become very simple, requiring only optoelectronic conversion, filtering and linear amplification. This shifting of the complex functionality away from the remote site allow cheap, reliable, small and light-weight radio access points with low power consumption to be deployed. In this paper, we show that an electroabsorption modulation(EAM) may be used as a single component in such a radio access point, as a passive transceiver for small-sized cell(picocells).

Radio-on-Fiber 액세스시스템 기술

  • 박종대;남상식;박권철
    • The Magazine of the IEIE
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    • v.30 no.3
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    • pp.81-85
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    • 2003
  • The advantages of using analogue optical networks for delivering radio signals from a central location to many remote antenna sites have been recognized. In a telecommnications context, radio signals may be for fixed radio access, cordless or mobile networks, but the same principles apply. By making use of the high bandwidth, low loss characteristics of optical fiber, all high frequency and signal processing functions can be performed centrally and signals can then be transported over the optical network directly at the carrier frequency. The remote sites then become very simple, requiring only optoelectronic conversion, filtering and linear amplification. This shifting of the complex functionality away from the remote site allow cheap, reliable, small and light-weight radio access points with low power consumption to be deployed. In this paper, we show that an electroabsorption modulation(EAM) may be used as a single component in such a radio access point, as a passive transceiver for small-sized cell(picocells).

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Electrical and Optical Properties of Asymmetric Dielectric/Metal/Dielectric (D/M/D) Multilayer Electrode Prepared by Radio-Frequency Sputtering for Solar Cells

  • Pandey, Rina;Lim, Ju Won;Lim, Keun Yong;Hwang, Do Kyung;Choi, Won Kook
    • Journal of Sensor Science and Technology
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    • v.24 no.1
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    • pp.15-21
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    • 2015
  • Transparent and conductive multilayer thin films consisting of three alternating layers FZTO/Ag/$WO_3$ have been fabricated by radio-frequency (RF) sputtering for the applications as transparent conducting oxides and the structural and optical properties of the resulting films were carefully studied. The single layer fluorine doped zinc tin oxide (FZTO) and tungsten oxide ($WO_3$) films grown at room temperature are found to have an amorphous structure. Multilayer structured electrode with a few nm Ag layer embedded in FZTO/Ag/$WO_3$ (FAW) was fabricated and showed the optical transmittance of 87.60 % in the visible range (${\lambda}=380{\sim}770nm$), quite low electrical resistivity of ${\sim}10^{-5}{\Omega}cm$ and the corresponding figure of merit ($T^{10}/R_s$) is equivalent to $3.0{\times}10^{-2}{\Omega}^{-1}$. The resultant power conversion efficiency of 2.50% of the multilayer based OPV is lower than that of the reference commercial ITO. Asymmetric D/M/D multilayer is a promising transparent conducting electrode material due to its low resistivity, high transmittance, low temperature deposition and low cost components.

Quasi-phase matched optical parametric oscillators using periodically poled $KNbO_3$ crystals (주기적으로 분극 반전된 $KNbO_3$를 이용한 준위상 정합 광 매개 진동자)

  • Lee Gwang Jo;Kim Jung Hyeon;Im Min Ho;O Hyeon Ho;Lee Don Hui;Yun Chun Seop
    • Proceedings of the Optical Society of Korea Conference
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    • 2003.02a
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    • pp.230-231
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    • 2003
  • $KNbO_3$is one of the best materials for efficient nonlinear frequency conversion, due to its large nonlinear optical coefficient ($d_{33}$ = 20.6 pm/V), wide transparency range (0.4 ~ 5 $\mu$m) and freedom from photorefractive effects. Quasi-phase-matched second harmonic generation using periodically poled $KNbO_3$ (PPKN) crystals has been reported. Here we report on fabrication of PPKN and demonstration of a pulsed optical param etric oscillator (QPM OPO) pumped by an Nd:YAG laser. (omitted)

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Forward Raman amplification for the narrow band Stokes line by double-pass fiber Raman scheme in multi-mode fiber

  • Hwang, In-Duk;Lee, Choo-Hie
    • Proceedings of the Optical Society of Korea Conference
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    • 2000.02a
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    • pp.238-239
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    • 2000
  • The optical fibers are an interesting medium for effective tunable optical frequency conversion in the spectral range of UV, Visible, and near-IR through the nonlinear processes. A number of papers for developing the wideband and flat-gain amplifier for the WDM system applications through the combination of EDFA or thulium-doped fluoride fiber amplifier and Raman amplifier, are reported$^{(1)}$ . Even though a variety of papers related to Raman amplifications are published, the amplification with the feedback of the residual pump is not investigated yet. Accordingly, in this paper, we report the characteristics of forward Raman amplification by the simple and double-pass fiber Raman configuration through the feedback of residual pump beam. (omitted)

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