• Journal of the Optical Society of Korea
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• v.20 no.4
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• pp.464-469
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• 2016

All-optical non-return-to-zero (NRZ) -to- return-to-zero (RZ) data-format conversion has been successfully demonstrated using a semiconductor optical amplifier in a fiber-loop mirror (so-called SOA-loop mirror) with a continuous-wave (CW) holding beam. The converted RZ signal after pulse compression has been used to create a 40 Gb/s OTDM (Optical Time Division Multiplexing) signal. Here is proposed an NRZ-to-RZ conversion method without any additional optical clocks, unlike conventional methods based on optical AND logic. In addition, it has the merit of operating at various bit-rate speeds without any controlling device. Moreover, it has a simple structure, and it can be used for all-optical bit-rate-flexible clock recovery.

• Korean Journal of Optics and Photonics
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• v.17 no.1
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• pp.68-74
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• 2006

We have extracted an optical clock signal from a return-to-zero(RZ) pseudorandom bit sequence(PRBS) and non-return-to-zero(NRZ) PRBS data in a pulsation multi-section laser diode with DFB reflector. The ms timing jitter achieved less than 1 ps for the input 11.727 Gbit/s RZ PRBS and NRZ PRBS data. The PRE data wasconverted from the NRZ data using an NRZ to pseudo-return to zero(PRZ) converter module. The optical clock was extracted from the PRZ data which contains the clock components. Although the input PRZ data gives a timing jitter of 2 ps, the extracted clock has timing jitter of ${\~}$1 ps.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.203-204
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• 2006

We present and demonstrate a novel method of alternate-phase return-to-zero (RZ) signal generation and pulse-amplitude equalization simultaneously in a rational harmonic mode-locked fiber ring laser, using a dual-drive Mach-Zehnder (MZ) modulator. By adjusting the voltages applied to both arms of the modulator, the rational harmonic mode-locked pulse trains are equalized in their amplitudes. In addition to that, the amplitude-equalized pulse trains multiplying the repetition rate at ${\sim}10\;GHz$ have alternate $\pi$ phase difference between adjacent pulses. The alternate-phase RZ signal generated by the proposed method enhances transmission performance through the single-mode fiber (SMF) links without dispersion compensation.

• Korean Journal of Optics and Photonics
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• v.16 no.1
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• pp.27-33
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• 2005

In this paper, a new wavelength converter using an SOA(Semiconductor Optical Amplifier)-loop-mirror for NRZ(NonReturn to Zero) optical data has been proposed and experimentally demonstrated. Conventional nonlinear fiber-loop-mirror methods can perform RZ-to-RZ, NRZ-to-RZ, and RZ-to-NRZ data format conversion, but NRZ-to-NRZ conversion has not been demonstrated until now. The experiment for the conversion from a 1300 nm NRZ data signal at 1.5 Gbps to a 1550 nm NRZ data one is successfully performed using a fiber-loop-mirror with 1300 nm-SOA.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.9
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• pp.57-64
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• 2004

In this paper, we propose a RZ/HRZ mixture data transmission method for the asynchronous circuit design to reduce Power consumption. The dual-rail data with Rf decoding scheme is used to design asynchronous circuit, and it is easy to get a completion signal of the data validity from the native data as contrasted with sin91e-rail. However, the dual-rail scheme suffers from large chip area and increasing of Power consumption from all signals by the switching of the return-to-zero. We need to diminish number of circuit switching. The proposed RZ/HRZ data transmission reduces a switching activity to about 50% and it shows 23% lower power consumption than the conventional dual-rail coding with RZ's.

• Journal of the Optical Society of Korea
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• v.13 no.2
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• pp.227-233
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• 2009

We investigated the polarization-mode dispersion (PMD) tolerance for 40Gb/s non-return to zero (NRZ), duobinary NRZ, return to zero (RZ), carrier-suppressed RZ (CS-RZ), and duobinary-carrier-suppressed RZ (DCS-RZ) modulation formats with a forward error correction (FEC) coding. The power penalty has been calculated as a measure of the system performance due to PMD. After comparison of the PMD tolerance of various modulation formats, our results suggest that RZ signals have the best tolerance against the effect of first-order PMD only. The duobinary NRZ modulation format is most resilient to PMD when both first- and second-order PMD are considered. However, the duobinary NRZ modulation format is the most sensitive to the incident angle of the input signal to a fiber axis in the presence of first- and second-order PMD, leading to incident angle-dependent power penalty. The coding gain by FEC can cope with the power penalties induced by first- and second-order PMD up to a DGD value of 16ps.

• Journal of the Korea Society of Computer and Information
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• v.17 no.8
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• pp.51-60
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• 2012

I propose the 5Gbps/1.25Gbps WDM/TDM hybrid Passive Optical Network(PON) with inverse RZ(Return to Zero) code coded downstream and NRZ(Non Return to Zero) upstream re-modulation and analyze its performance by performing simulation with MATLAB. The results have shown that an optical line termination (OLT) can be connected to 8, 16 optical network unit (ONU)s with the Bit Error Rate(BER) of $10^{-9}$ when the distance between OLT and ONU is 10Km and transmitted optical powers are more than -3.8, -0.9dBm, respectively. The proposed WDM/TDM hybrid PON system can solve the problem of data rate limit in upstream which happened in the conventional TDM PON because the upstream data rate is proportional to ONU and does not require a light source in ONU and its control circuits in OLT, thus can be a useful technology for asymmetric optical subscriber networks.

• JSTS:Journal of Semiconductor Technology and Science
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• v.17 no.3
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• pp.378-386
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• 2017

A return-to-zero (RZ) digital-to-analog converter (DAC) with a tri-state switching scheme is proposed in this paper. The proposed scheme provides a triple weight output for RZ operation by using a conventional differential current switch and simple pseudo-differential F/Fs. The RZ function is realized with only two additional transistors in each F/F cell, which results in a power dissipation increase of less than 5%. To verify the performance of the proposed method, a 10-bit RZ DAC is fabricated using standard 180-nm CMOS technology. Measured results show that the worst SFDR performances are 60 dBc and 55 dBc in the 1st and 2nd Nyquist bands, respectively, when operating at 650 MHz clock frequency. The total power consumption is 64 mW, and the active area occupies $0.25mm^2$.

• Journal of the Optical Society of Korea
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• v.13 no.3
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• pp.361-366
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• 2009

We propose the performance enhancing method optimization of an asynchronous 2.5 Gbps/1.25 Gbps optical subscriber network with inverse RZ (Return to Zero) coded downstream and NRZ (Non Return to Zero) upstream re-modulation by adjusting threshold level control of a receiver. We theoretically analyze the BER (Bit Error Rate) performance by modeling the occurrence of BER by simulation with MATLAB according to the types of downstream data. The results have shown that the normalized threshold level in an optical receiver could be saturated at 1/3 as the SNR (Signal to Noise Ratio) increases. The needed SNR for obtaining the BER $10^{-9}$ can be reduced by $\sim$5 dB by optimizing the normalized threshold level at 1/3 instead of by using the conventional receiver with threshold level of 0.5. The proposed system can be a useful technology for asynchronous optical access networks with asymmetric upstream and downstream data rates, because the improved minimum receiving power could replace a light source with a source with lower power and lower cost in an OLT (Optical Line Termination).

• Journal of the Korea Society of Computer and Information
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• v.15 no.3
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• pp.65-72
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• 2010

We propose the asymmetric 2.5Gbps/622Mbps PON(Passive Optical Network) in order to reduce the bandwith of filter at receiver with inverse RZ(Return to Zero) code coded downstream and NRZ(Non Return to Zero) upstream re-modulation. I theoretically analyze BER(Bit Error Rate) performance and the power sensitivity with the optimal threshold level by performing simulation with MATLAB according to the types of downstream data. The results have shown that the optimal threshold level at the optical receiver could be saturated at 0.33 as the optical received power increase more than -26dBm to keep $10^{-12}$ of BER to a minimum. Also the power sensitivity is more improved by about 3dB by fixing the threshold level at 0.33 than the conventional receiver. The proposed system can be a useful technology for optical access networks with asymmetric upstream and downstream data rates because the optical receiver can be used without controlling threshold levels and that does not require a light source in optical network unit (ONU) and its control circuits in the optical line termination (OLT).