• Journal of Communications and Networks
• /
• v.9 no.4
• /
• pp.368-376
• /
• 2007

The large potential bandwidth available in wavelength-division multiplexed optical networks makes this technology of crucial importance for satisfying the ever increasing capacity requirements of the next-generation Internet. In this scenario, the routing and wavelength assignment(RWA) problem that concerns determining the optical paths and wavelengths to be used for connection establishment in a wavelength-routed network, is still one of the most important open issues. In this paper we propose a new online dynamic grooming-capable RWA heuristic scheme working on wavelength division multiplexing(WDM) networks as a multistage selection process. The proposed algorithm is transparent with respect to the presence of wavelength converters, achieves very low connection rejection ratios with minimal computational complexity and is appropriate for the modern multilayer optical circuit and wavelength switched networks with sparse wavelength conversion capability.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.43 no.5 s.347
• /
• pp.68-76
• /
• 2006

We propose a low noise broadband light source (BLS) and investigate a cost-effective wavelength division multiplexing-passive optical network (WDM-PON) for the convergence of broadcasting and data service. The proposed BLS is used for an injection light of wavelength-locked Fabry-Perot laser diodes (F-P LD) and helps the color-free operation of dense WDM-PON (DWDM-PON). In addition, we apply this BLS to a optical source for overlay of digital broadcasting channel on the WDM-PON.

• Korean Journal of Optics and Photonics
• /
• v.14 no.4
• /
• pp.351-354
• /
• 2003

We present a 12.5-GHz interleaved bidirectional ultra-dense wavelength-division-multiplexing transmission over a conventional single mode fiber of 80 km achieving spectral efficiency as high as 0.8-bit/s/Hz. The beat-frequency-locking method is used to stabilize the channel frequency within $\pm$200 MHz error. To facilitate the identification of multiple beat frequency signals, we use a radio-frequency spectrum analyzer. The bidirectional transmission penalty is about 0.3 dB compared with the unidirectional transmission over the same fiber.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.17 no.6
• /
• pp.1419-1424
• /
• 2013

Passive optical networks (PONs) are the emerging solution for access networks since PONs provide high bandwidth and the low operation cost. In recent, the new solution in access networks is TWDM PON which is a mixture of WDM (wavelength-division multiplexing) and TDM (time-division multiplexing). This paper proposes a new MAC (media access control) protocol for TWDM PON. In addition, this paper proposes and evaluates a new dynamic bandwidth allocation method for TWDM PON.

• Journal of the Optical Society of Korea
• /
• v.20 no.5
• /
• pp.557-562
• /
• 2016

In this paper, for the first time, the transmission performances of long-haul 100-Gb/s direct detection optical OFDM (DDO-OFDM) and coherent optical OFDM (CO-OFDM) wavelength division multiplexing (WDM) systems are compared by simulation. It provides specific guides for system parameter selection to get a high-performance and cost-effective OFDM WDM system. Specifically, the comparison involves three aspects: launched power is investigated to achieve better system performance; laser linewidth is numerically investigated to choose cost-effective laser; system dispersion tolerances with different laser linewidths are analyzed to further reveal the advantages and disadvantages of these two detecting methods, direct detection and coherent detection, in long-haul OFDM WDM system.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.23 no.7
• /
• pp.1785-1796
• /
• 1998

This paper is concerned with the relationships between optimal number of wavelengths and tuning time in time division multiplexing(TDM) scheduling on wavelength division multiplexing(WDM) optical passive star networks. We assume that the traffic is nonuniform and each node has a tunable transmitter and a fixed receiver. Each node transmits spckets to all other nodes. Most of the earlier protocols on TDM based scheduling for WDM star networks [7, 8, etc.] use whold given wavelength chnnels. But in this paper, we investigate the optimal number of wavelengths that yidels minimum frame length when tuning time exists. It appears within the availble number of wavelengths that yields minimum frame length when tuning time exists. It appears within the available number of wavelengths. We analyze the relationships between optimal number of wavelengths and tuning time by experiments. We analyze the reationships between optimal number of wavelengths and tuning time by experiments. We also discuss on the possibility of reduction of frame length by increasing the number of nodes trans-mitters and receivers.

• Journal of the Institute of Convergence Signal Processing
• /
• v.21 no.4
• /
• pp.162-169
• /
• 2020

In this paper, we attempted a qualitative understanding of mutual injection locking without rigorous mathematics, and analyzed the proposed mutual injection locked light source. Also, a low-cost WDM-PON light source based on mutual injection locking using two unpolarized Fabry-Perot Laser Diodes (F-P LDs), was implemented. The RIN (Relative Intensity Noise) characteristic for the wavelength change of the F-P LD was measured, and when the variable wavelength range was 2.07 nm, it showed a RIN of at least -110 dB/Hz.

• Journal of Korean Institute of Industrial Engineers
• /
• v.26 no.4
• /
• pp.296-305
• /
• 2000

Virtual wavelength path (VWP) is the optical path when a wavelength conversion is possible in a wavelength division multiplexing (WDM) network that is transmission infrastructure for the next generation high speed backbone networks. To achieve efficient design for VWP networks, we must consider VWP routing, wavelength assignment, and wavelength conversion while satisfying many technical constraints of the WDM networks. In this study we propose an integrated model for efficient VWP design in WDM networks. We also develope a 3-phase algorithm, each of which deals with routing, wavelength assignment and route and wavelength reassignment, respectively. In our computational experiments, phase 1 algorithm can solve the problem to the optimality for medium size test networks. Phase 2 algorithm is an efficient heuristic based on a reduced layered network and can give us an effective wavelength assignment. Finally, phase 3 algorithm reconfigure VWP routing and its wavelength assignment to concentrate wavelength conversion nodes in the suggested VWP network.

• Journal of Advanced Navigation Technology
• /
• v.14 no.6
• /
• pp.831-837
• /
• 2010

Optimal conditions of 40 Gbps RZ format for implementation of optical time division multiplexing/wavelength division multiplexing (OTDM/WDM) transmission system are induced by analyzing and comparing performance depending on duty cycle and extinction ratio (ER). Optical phase conjugator (OPC) and inline dispersion management (DM) are applied into optical transmission links for compensating signal distortion due to chromatic dispersion and nonlinearity of fiber. It is confirmed that RZ format of 0.25 duty cycle is less effected by system performance change depending on ER and it is suitable for multiplexing to 160 Gbps signal through OTDM. Also, it is shown that performance improvement of RZ format determined by same net residual dispersion (NRD) is more increased as residual dispersion per span (RDPS) becomes large.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.25 no.9A
• /
• pp.1405-1412
• /
• 2000

In this paper, we propose an efficient dynamic wavelength assignment algorithm in distributed WDM (Wavelength-Division Multiplexing) networks without wavelength conversion. The algorithm tries to assign a locally-most-used wavelength distributedly on a fixed routing path. We first formulate our algorithm by using the concept of a sample space which consists of optical fibers connected to nodes on a routing path of a lightpath to be assigned a wavelength. In particular, we analyze the blocking performance mathematically as compared with that of the most-used (MU) wavelength assignment algorithm previously proposed for WDM networks under centralized control. We also obtain numerical results by simulation on the blocking performance of other centralized/distributed wavelength assignment algorithms as well as our algorithm using the M/M/c/c dynamic traffic model. Consequently, we show that analytical results match simulation results and that our algorithm is efficient in distributed WDM networks in terms of blocking performance, control traffic overhead and computation complexity.