• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2014.05a
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• pp.705-706
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• 2014

This paper proposes a new dynamic bandwidth allocation algorithm for an XG-PON (10-Gbps-capable passive optical network) system. In the XG-PON system, an ONU (optical network unit) does not explicitly send it request to an OLT (optical line termination). The OLT monitors the upstream bandwidth usage of the ONU to estimate the request of the ONU. Then the OLT performs a dynamic bandwidth allocation process based on the estimated requests.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2014.10a
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• pp.152-153
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• 2014

This paper proposes a new dynamic bandwidth allocation algorithm for an XG-PON (10-Gbps-capable passive optical network) system in which an ONU (optical network unit) does not explicitly send its request to an OLT (optical line termination). To estimate the request of the ONU, the OLT monitors the upstream bandwidth usage of the ONU and periodically allocates a probe slot to the ONU.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.05a
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• pp.449-450
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• 2015

This paper describes performance evaluation results of a new dynamic bandwidth allocation algorithm for an XG-PON (10-Gbps-capable passive optical network) system without using an explicit request. An ONU (optical network unit) does not send its request to an OLT (optical line termination). The OLT monitors the upstream bandwidth usage of the ONU to estimate the request of the ONU.

• 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.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.05a
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• pp.447-448
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• 2015

This paper proposes a new dynamic wavelength allocation algorithm for TWDM PON (time and wavelength division multiplexed passive optical network) which comprises of multiple ONUs (optical network units) which have low-speed wavelength tuner. The wavelength tuner requires large amount of frame times to tune its wavelength. An OLT (optical line termination) performs a dynamic bandwidth allocation after the wavelengths of ONUs are determined.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2014.10a
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• pp.150-151
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• 2014

This paper evaluates performance of a dynamic wavelength and bandwidth allocation algorithm of TWDM PON (time and wavelength division multiplexed passive optical network) which consists of an OLT (optical line termination) and multiple ONU (optical network unit). The allocation algorithm reduces the number of upstream wavelengths to save power. Using self-similar traffic, we simulate TWDM PON systems and measure the average packet delay and the average number of upstream wavelengths.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2014.05a
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• pp.699-700
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• 2014

This paper proposes a new dynamic wavelength and bandwidth allocation algorithm for TWDM PON (time and wavelength division multiplexed passive optical network) which consists of an OLT (optical line termination) and multiple ONU (optical network unit). The proposed algorithm dynamically limits the number of the upstream wavelengths based on the request amount of ONUs to save power.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.2C
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• pp.160-169
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• 2002

An ATM-PON (Passive Optical Network) system consists of an OLT (Optical Line Termination), multiple ONUs (Optical Network Units) and the optical fiber which has a PON (Passive Optical Network)configuration with a passive optical splitter. To avoid cell collisions on the upstream transmission, an elaborate procedure called as ranging is needed when a new ONU is installed. The ONU can send upstream cells according to the grant provided by the OLT after the procedure. To prevent collisions being generated by the variation of several factors, OLT must performs continuously the cell phase monitoring. It means that the OLT predicts the expected arrival time, monitors the actual arrival time for all upstream cells and calculates the error between the times. Accordingly, TC (Transmission Convergence) chip in the OLT needs a predictor which predicts the time that the cell will arrive for the current grant. In this paper, we implement the predictor by using shift registers of which the length is equivalent to the equalized round trip delay. As each register consists of 8 bit, OLT can identify which ONU sends what type of cell (ranging cell, user cell, idle cell, and mini-slot). Also, TC chip is designed to calculate the effective bandwidth for all ONUs by using the function of predictor. With the time simulation and the measurement of an implemented optical board, we verify the operation of the predictor.

• 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).

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.5C
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• pp.454-464
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• 2002

In the ATM-PON (Asynchronous Transfer Mode-Passive Optical Network), the downstream cell transmitted by an OLT is broadcast to all ONUs. The ONU receives selectively its own cells by VP filtering. On the other hand, the upstream cell can be transmitted by ONU in the case of receiving a grant from the OLT. After providing the grant to an ONU, the OLT expects the arrival of a cell after an elapse of the equalized round trip delay. ITU-T G.983.1 recommends that one bit error is allowed between the expected arrival time and the actual arrival time at the OLT. Because the ONU processes the different delay to each type of grant (ranging, user cell, and mimi-slot grant), it is not simple to design the transmission part of ONU. In this paper, we implement a grant processor which provides the delay accurately in the ONU TC chip with the FPGA. For the given equalized delay, it deals with the delay for the cell, the byte, and the bit unit by using the shift register, the byte counter, and the D flip-flop, respectively. We verify the operation of the grant processor by the time simulation and the measurement of the optical board output.