• ETRI Journal
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• v.27 no.5
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• pp.484-490
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• 2005

We fabricated 40 Gb/s front-end optical receivers using spot-size converter integrated waveguide photodiodes (SSC-WGPDs). The fabricated SSC-WGPD chips showed a high responsivity of approximately 0.8 A/W and a 3 dB bandwidth of approximately 40 GHz. A selective wet-etching method was first adopted to realize the required width and depth of a tapered waveguide. Two types of electrical pre-amplifier chips were used in our study. One has higher gain and the other has a broader bandwidth. The 3 dB bandwidths of the higher gain and broader bandwidth modules were about 32 and 42 GHz, respectively. Clear 40 Gb/s non-return-to-zero (NRZ) eye diagrams showed good system applicability of these modules.

• ETRI Journal
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• v.21 no.3
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• pp.1-5
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• 1999

A clock and data recovery circuit with a phase-locked loop for 10 Gb/s optical transmission system was realized in a hybrid IC form. The quadri-correlation architecture is used for frequency-and phase-locked loop. A NRZ-to-PRZ converter and a 360 degree analogue phase shifter are included in the circuit. The jitter characteristics satisfy the recommendations of ITU-T. The capture range of 150 MHz and input voltage sensitivity of 100 mVp-p were showed. The temperature compensation characteristics were tested for the operating temperature from -10 to $60^{\circ}C$ and showed no increase of error. This circuit was adopted for the 10 Gb/s transmission system through a normal single-mode fiber with the length of 400 km and operated successfully.

• ETRI Journal
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• v.30 no.2
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• pp.255-260
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• 2008

We compare the performance of a wavelength remodulated wavelength-division-multiplexed passive optical network implemented using Manchester-coded or inverse-return-to-zero (IRZ)-coded signal downstream and non-return-to-zero remodulated signal upstream. We investigate the effects of varying differences between downstream and upstream bit rates on the two coding schemes. When the bit rate ratio of upstream to downstream is less than or equal to 50%, the performance of Manchester coding is better than that of IRZ coding. However, when the bit rate ratio of upstream to downstream is higher than 50%, Manchester code requires appropriate time delay between upstream and downstream signals, whereas IRZ code needs reduced extinction ratio in the downstream signal.

• ETRI Journal
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• v.30 no.2
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• pp.249-254
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• 2008

In this paper, we demonstrate an electrically band-limited carrier-suppressed return-to-zero (EB-CSRZ) signal generator operating up to a 10 Gbps data rate comprising a single-stage Mach-Zehnder modulator and a wideband signal mixer. The wideband signal mixer comprises inverter stages, a mixing stage, and a gain amplifier. It is implemented by using a 0.13 ${\mu}m$ CMOS technology. Its transmission response shows a frequency range from DC to 6.4 GHz, and the isolation response between data and clock signals is about 21 dB at 6.4 GHz. Experimental results show optical spectral narrowing due to incorporating an electrical band-limiting filter and some waveform distortion due to bandwidth limitation by the filter. At 10 Gbps transmission, the chromatic dispersion tolerance of the EB-CSRZ signal is better than that of NRZ-modulated signal in single-mode fiber.

• ETRI Journal
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• v.31 no.3
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• pp.348-350
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• 2009

To fit the limited volume and power consumption of the passive radio frequency transmission system of the electronic time fuze, an improved coded mark inversion (CMI) is proposed in this letter. From the performance analysis, the energy transmission efficiency of this encoding method is at least 50% higher than that of CMI and NRZ. Finally, the experiment results show that by adopting this improved CMI, the change of DC voltage through magnetic coupling is lower than 0.2 V when the accuracy of data transmission is above 99.5%.

• Information and Communications Magazine
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• v.26 no.5
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• pp.10-14
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• 2009

본고에서는 RGB LED전광판을 이용한 가시광 정보 방송시스템에 대하여 기술한다. 현재 상용 RGB LED로 구성된 전광판에 기존의 디스플레이 기능 외에 디지털 데이터 변조기능을 부가하였다. 전광판의 규격은 1단 2열 구조로 설정하였고, 전광판의 모든 RGB LED는 NRZ 10/20 Mbps신호로 동시에 변조가 가능하도록 설계하였다. LED가 공기 중으로 방사한 가시광 신호의 성능은 수신기를 통해 데이터를 검출한 뒤에 비트오율을 측정하여 검증하였다. 전광판 RGB LED를 최대한 활용하여 LED를 10 Mbps 데이터 신호로 변조하여 방송했을 때 에러 없이 5.6m이상 전송이 가능하였고, 전송 속도가 20 Mbps인 경우는 $10^{-6}$비트오율 기준으로 5.6m까지 방송이 가능하였다. 향후 전광판 LED가 통신용으로 설계된 제품으로 대체되어 변조 특성이 좋아지고, 전광판 구조가 커져 전광판이 방출하는 전체 광출력이 증가하면 전송 특성이 보다 향상될 것으로 예상된다.

• ETRI Journal
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• v.28 no.6
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• pp.826-829
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• 2006

A novel method for optical phase shaped binary transmission (PSBT) generation has been recently reported and experimentally evaluated. An amelioration of the optical signal-to-noise ratio (OSNR) sensitivity of the optical PSBT modulation format is proposed with the application of the concepts of enhanced electrical PSBT signal generation. Enhanced optical PSBT is proposed here as a modulation format producing a 0.7 dB gain in OSNR sensitivity compared to OPSBT, while maintaining a good robustness to group velocity dispersion: 100 ps/nm for enhanced optical PSBT and 120 ps/nm for optical PSBT, compared to 50 ps/nm for standard NRZ signals.

• JSTS:Journal of Semiconductor Technology and Science
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• v.3 no.4
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• pp.188-193
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• 2003

This paper describes a novel burst-mode clock and data recovery (CDR) circuit which can be used for 622Mbps burst mode applications. The CDR circuit is basically a phase locked loop (PLL) having two phase detectors (PDs), one for the reference clock and the other for the NRZ data, whose operations are controlled by an external control signal. This CDR was fabricated in a 1-poly 5-metal $0.25{\;}\mu\textrm{m}$ CMOS technology. Jitter generation, burst/continuous mode data receptions were tested. Operational frequency range is 320Mhz~720Mhz and BER is less than 1e-12 for PRBS31 at 622Mhz. For the same data sequence, the extracted clock jitter is less than 8ps rms. Power consumption of 100mW was measured without I/O circuits.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.8
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• pp.119-125
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• 1995

Strained multiple quantum well(SMQW) PBH-DFB-LDs emitting at 1.55$\mu$m wavelength has been fabricated using OMVPE and LPE crystal growth tecnique. Using the SMQW active layer, a linewidty enhancement factor of 2.65 was obtained at lasing wavelength and consequnently, packaged 42 modules showed a very low average chirp of 0.44nm at 2.5Gbps NRZ direct modulation. The 77 devices showed average threshold current of 8.72mA and average slope efficiency of 0.181 mW/mA, and single longitudinal mode operation with SMSR larger than 30dB up to 5mW. Among the 77 devices, standard deviation of lasing wavelength of 3.57nm was obtained owing to a good crystal growth uniformity.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.32 no.2
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• pp.50-58
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• 1983

In this paper, a field trial of the Korean-made optical fiber communication system is described. This system was installed between Gu-Ro and Ann-Yang telephone offices on November 1981, and carries a 44.7Mb/s NRZ signal(672 voice channel equivalent). For this trial, optical fiber cable, optical terminal equipment, optical repeater, fusion splicer and measurement equipment have been developed. Employing graded index optical fiber at a wave length of $0.85\;\mu\textrm{m}$, average optical attenuation and splicing losses of 3.6 dB/km and 0.4 dB, resectively, were realized. With link margins of 8~20dB and bit error rate of less than $10^{-10}$, this system has been carrying live traffic between Seoul and Ann Yang telephone offices.