• Proceedings of the Optical Society of Korea Conference
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• 2006.07a
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• pp.363-364
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• 2006

We developed 60 GHz analog optical transmitter modules for radio-over-fiber (RoF). They were consisted of an electroabsorption modulator (EAM), impedance matching circuit, and amplifier. The characteristics of fabricated modules were investigated by measuring the signal-to-noise ratio and the noise figure of the 60 GHz RoF link.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1983.10a
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• pp.32-34
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• 1983

In this paper, an analog optical filter link is evaluated for the transmission of baseband video signals over a single fiber. LED and PIN photo diode are used as the optical source and the detector. Frequency response of the system, DP, DG and SNR are measured.

• Journal of the Optical Society of Korea
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• v.18 no.4
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• pp.330-334
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• 2014

In this paper, we present an incoherent dual-parallel modulation linearized optical link employing two different optical wavelengths. Comparing with previous dual-parallel modulation, this linearization method prevents the recreation of distortion products and can be readily implemented. Furthermore, a dual-wavelength dual-parallel modulation linearized optical link constructed with the commercially available devices is experimentally demonstrated with a spurious-free dynamic range of $122.5dB.Hz^{4/5}$. More than 25 dB suppression of the intermodulation distortion, 15.6 dB improvement of spurious-free dynamic range and 1.5 dB improvement of compression dynamic range are achieved after linearization.

• 한국정보통신설비학회:학술대회논문집
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• 2006.08a
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• pp.15-18
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• 2006

We have proposed a broadband analog feedforward optical transmitter using a wideband $180^{\circ}$ hybrid coupler instead of conventional frequency-sensitive phase shifter with the narrow bandwidth property using a wideband $180^{\circ}$ hybrid coupler, the wide-band linearization technique enhances the linearity of the feedforward optical transmitter. In two-tone cases, the $3^{rd}-IMD$ products was enhanced more than 10 dB in 385 MHz range(1.375$\sim$l.76 GHz).

• Journal of IKEEE
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• v.13 no.4
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• pp.96-102
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• 2009

We investigate the characteristics of RJ (random jitter) in an analog fiber-optic link employing a MZM (Mach-Zehnder modulator) and an EDFA (Erbium-doped fiber amplifier). RJ has been measured using two methods, one of which derived from the noise spectrum of a RF spectrum analyzer and the other from the histogram data of a sampling oscilloscope. If the optical power and/or the RF power input to the MZM increase, RJ decreases due to the output signal power increase. For the optical link without EDFA, the minimum RJ is about 1 ps at an RF power of 10 dBm and an optical power of 8 dBm measured using the noise spectrum method. For the optical link with an EDFA, RJ decreases toward a jitter floor as the EDFA gain increases. If the gain increases further, it has been observed that RJ increases from the minimum. If the EDFA gain is fixed, RJ is smaller for the case of larger optical input power. As the EDFA gain increases, RJ reduction rate becomes greater for the case of lower optical input power.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.37 no.7
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• pp.24-30
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• 2000

In this paper, we proposed an fiber-optic transceivers based on the analog optical transmission techniques of incorporating the SCM (subcarrier multiplexing) and WDM (wavelength-division multiplexing ) method, which can be used to transmission of IMT-2000 and PCS wireless frequency band and analyzed overall those parameters related with fabrication. Especially in the impedance matching network between RF signal and LD, we proposed the method of deriving optimal performance using simulation techniques. In the frequency band of 1.7GHz∼2.25GHz, experimental data for the gain flatness and the noise floor of the optical link were also presented $\pm$1.5dB and -130dBm respectively when the link Rain was 0dB.

• 한국정보통신설비학회:학술대회논문집
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• 2007.08a
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• pp.19-21
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• 2007

디지털용 Uncooled DFB 레이저 다이오드를 이용하여 광대역 아날로그 피드포워드 광송신기를 제작하였다. 광송신기의 상호변조왜곡 성분 및 잡음성분을 제거하기 위해 광 피드포워드 보상기법을 사용하였으며, 다중서비스를 위해 $2.05{\sim}2.60$ GHz(550 MHz)에서 상호 변조왜곡 성분이 10 dB 이상 억제되었고, 상대강도잡음은 1.5 dB 이상 억제되었다. 2.3 GHz 에서 3 차 상호변조왜곡성분이 21.3 dB, SFDR 이 7.11 dB 향상된 결과를 얻었다. 또한 단일 모드 광섬유 전송 실험을 통해 전송길이에 따른 3 차 상호변호 왜곡성분의 크기 변화를 확인하였다.

• Journal of IKEEE
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• v.13 no.4
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• pp.103-109
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• 2009

We report an efficient jitter reduction technique in an analog fier-optic link employing a Mach-Zehnder modulator followed by an erbium-doped fiber amplifier. By adjusting the modulator-bias to $0.089V_{\pi}$, we could increase the RF gain up to 10.65 dB for 10 GHz RF signal and reduce the random jitter by 46.5%, max, at an input optical power of -0.11 dBm to the EDFA.

• Journal of information and communication convergence engineering
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• v.13 no.3
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• pp.167-171
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• 2015

A radio over fiber (RoF) system is a kind of analog optical transmission system and considered as a strong candidate for the next-generation fronthaul link in the future mobile network. In RoF systems, nonlinearity compensation is essential to increase the link capacity. In this paper, we propose a nonlinearity detection and compensation scheme using a monitoring channel in RoF systems. A monitoring channel is added at the transmitter site and used for transmitting a reference signal in an RoF transmission. The nonlinearity in the RoF transmission is detected by comparing the received monitoring signal and the original reference signal at the receiver site. Finally, the nonlinearity is compensated at the receiver by giving the reverse function of the detected nonlinearity. Our results show that the proposed scheme can almost remove the error vector magnitude degradation induced by the nonlinearity in the RoF system.

• 한국정보통신설비학회:학술대회논문집
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• 2007.08a
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• pp.15-18
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• 2007

RoF 링크 시스템을 적용한 무선 근거리 통신망(IEEE 802.11b/g)의 중심 주파수 대역인 2.4 GHz에서 저가의 Febry-Perot 레이저 다이오드를 이용한 피드포워드 광송신기를 제작 및 측정 하였다. 제작된 피드포워드 광송신기의 측정 결과는 2.4 GHz에서 주신호의 간격이 10 MHz이고 크기가 -4 dBm인 입력 신호에서 피드포워드 보상기법을 적용하기 전보다 3차 상호 변조 왜곡 신호가 22.9 dB 개선되었다. 제작된 피드포워드 광송신기의 전자소자의 사양을 바탕으로 송신기 집적을 위한 RFIC회로(감쇄기, 증폭기)를 0.18 ${\mu}m$ 공정을 이용하여 설계하였다.