• Current Optics and Photonics
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• 제7권1호
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• pp.47-53
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• 2023

We propose a centralized passive-optical-network monitoring scheme using the resonance-spectrum properties of a Fabry-Perot cavity based on fiber Bragg gratings. Each cavity consists of two identical uniform fiber Bragg gratings and a varying cavity length or grating length, which can produce a unique single-mode resonance spectrum for the drop-fiber link. The output spectral properties of each cavity can be easily adjusted by the cavity length or the grating length. The resonance spectrum for each cavity is calculated by the transfer-matrix method. To obtain the peak wavelength of the resonance spectrum more accurately, the effective cavity length is introduced. Each drop fiber with a specific resonance spectrum distinguishes between the peak wavelength or linewidth. We also investigate parameters such as reflectivity and bandwidth, which determine the basic performance of the fiber Bragg grating used, and thus the output-spectrum properties of the Fabry-Perot cavity. The feasibility of the proposed scheme is verified using the Optisystem software for a simplified 1 × 8 passive optical network. The proposed scheme provides a simple, effective solution for passive-optical-network monitoring, especially for a high-density network with small end-user distance difference.

• ETRI Journal
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• 제30권2호
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• pp.301-307
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• 2008

As broadband access is evolving from digital subscriber lines to optical access networks, Ethernet passive optical networks (EPONs) are considered a promising solution for next generation broadband access. The point-to-multipoint topology of EPONs requires a time-division multiple access MAC protocol for upstream transmission. In this paper, we propose a new enhanced dynamic bandwidth allocation algorithm with fairness called EFDBA for multiple services over EPONs. The proposed algorithm is composed of a fairness counter controller and a fairness system buffer in the optical line terminal. The EFDBA algorithm with fairness can provide increased capability and efficient resource allocation in an EPON system. In the proposed EFDBA algorithm, the optical line termination allocates bandwidth to the optical network units in proportion to the fairness weighting counter number associated with their class and queue length. The proposed algorithm provides efficient resource utilization by reducing the unused remaining bandwidth made by idle state optical network units.

• 한국광학회:학술대회논문집
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• 한국광학회 2001년도 제12회 정기총회 및 01년도 동계학술발표회
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• pp.174-175
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• 2001

This paper theoretically demonstrates that our proposed method improves the Signal-to-Noise Ratio (SNR) of significantly increase the number of acceptable optical signals in FDMA(SCMA) systems. This method reduced Optical Beat Interference(OBI) by using CDMA.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 학술대회 논문집 정보 및 제어부문
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• pp.663-665
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• 2004

Ethernet-based passive optical network(EPON) technology is being considered as a promising solution for next-generation broadband access network. It must have the property of high efficiency, low cost, and support quality of service(QoS). A major feature for this new architecture is the use of a shared transmission media between all connected optical network unit(ONU). Hence, medium access control(MAC) arbitration mechanisms are essential for the successful implementation of EPON. In this paper we propose a simple dynamic bandwidth allocation(DBA) algorithm that improves the performance of network and supports IP-based multimedia applications with the bursty data traffic. In addition, we introduce analytic models of proposed algorithms and prove the system based on our algorithm to be asymptotically stable. Simulation results show the new DBA algorithm provides high bandwidth efficiency and low queueing delay of ONU in EPON.

• Current Optics and Photonics
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• 제4권3호
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• pp.186-192
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• 2020

This paper describes a real-time monitoring system in Ethernet passive optical networks (EPON) that uses burst-mode fiber Bragg grating (FBG) optical sensors. The FBG interrogation unit in the optical line terminal (OLT) transmits the monitoring wavelength to optical network units (ONUs). The FBG sensor unit in each ONU returns a burst-mode monitoring signal to the OLT. As the system applies time division multiple access (TDMA), a uniform Bragg wavelength can be used to monitor the EPON system. The FBG interrogation unit analyzes the received burst-mode monitoring signals and outputs fault information on the ONU branches in EPON. The simulation results show the effectiveness of the proposed monitoring system based on TDMA. In addition, we compared the proposed TDMA-based monitoring system with a WDMA-based monitoring system.

• Journal of the Optical Society of Korea
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• 제15권1호
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• pp.4-8
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• 2011

We have evaluated the performances of bidirectional optical amplifiers which were suited for the cost-effective implementation of amplified bidirectional passive optical networks (PONs). First, we measured the maximum gains of two simple bidirectional optical amplifiers implemented without using any optical components for the suppression of reflected signals. From the results, the maximum gains of two simple bidirectional amplifiers with a broadband light source (BLS) seeded optical source were limited to be 27 dB due to the reflection-induced in-band crosstalk, when the reflectance coefficients were measured to be -33 dB in both directions. Then, we have also implemented a bidirectional optical amplifier with two band splitters for the amplified bidirectional PON where the two different wavelength bands were allocated to the downstream and upstream signals transmission. In our measurement, we confirmed that the maximum gain of bidirectional optical amplifier with two band splitters could be increased to more than 30 dB owing to the efficient suppression of in-band crosstalk.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2014년도 춘계학술대회
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• pp.693-694
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• 2014

이 논문에서는 단위시간 이내에 동적대역할당 완료가 어려운 XG-PON (10-Gbps-capable passive optical network) passive optical networks) 시스템에 사용할 수 있는 새로운 pipeline 방식의 동적대역할당 방식을 제안한다. 제안한 방식에서는 request가 각각의 pipeline 블록에 즉시 입력되어 성능이 개선된다.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2015년도 춘계학술대회
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• pp.447-448
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• 2015

본 논문에서는 저속의 파장변환기를 갖는 ONU (optical network unit)로 구성된 TWDM PON(time and wavelength division multiplexed passive optical network)에 파장 할당 알고리즘을 제안한다. ONU는 파장을 변경할 때 많은 프레임시간을 소비하며 ONU별로 파장이 결정되면 그 결과를 바탕으로 OLT (optical line termination)는 동적대역할당을 실시한다.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2015년도 춘계학술대회
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• pp.449-450
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• 2015

이 논문에서는 XG-PON (10-Gbps-capable passive optical network) 시스템에서 전송요청을 사용하지 않는 동적대역할당 알고리즘의 성능을 평가한다. OLT (optical line termination)는 ONU(optical network unit)의 상향 대역폭 사용량을 monitoring 해서 ONU의 전송허가량을 추측한다.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2014년도 춘계학술대회
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• pp.705-706
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• 2014

이 논문에서는 XG-PON (10-Gbps-capable passive optical network) 시스템에 대한 새로운 동적대역할당 알고리즘을 제안한다. 이 논문에서 고려하는 XG-PON 시스템에서는 ONU (optical network unit)가 명시적으로 전송요청을 OLT (optical line termination)로 보내지 않는다. OLT는 ONU의 상향 대역폭 사용량을 monitoring하여 ONU의 전송허가량을 추측하고 이를 바탕으로 동적대역할당을 실시한다.