• Current Optics and Photonics
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• v.5 no.6
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• pp.711-720
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• 2021

A novel optical hybrid device that doubles the multilevel demodulation resolution by adding the optical interferometer with a waveguide crossover is proposed, theoretically analyzed and experimentally verified. We report two types of all-passive phase control schemes that will be referred to as a phase compensation scheme and a phase optimization scheme. We also apply the proposed phase control schemes to a 45° optical hybrid consisting of two parallel 90° optical hybrids together with the proposed phase control scheme for demodulating 8-level differential phase shift keying optical signals. Octagonal phase response with low wavelength sensitive excess loss of <0.8 dB over 31-nm-wide spectral range will be demonstrated in the InP-based material platform.

• Proceedings of the IEEK Conference
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• 1999.06a
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• pp.289-292
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• 1999

Random reference wave can be used to enhance selectivity and storage density of holograms. Hologram recording schemes with random reference waves generated by using a ground glass or various types of optical fibers are discussed. The random reference waves are also suitable for hybrid multiplexing methods.

• Current Optics and Photonics
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• v.3 no.5
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• pp.365-373
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• 2019

This paper investigates the performance of a hybrid single input multiple output radio frequency/free-space optics (SIMO-RF/FSO) communication system. Each SIMO-RF link is modeled as an independent and identically distributed (i.i.d.) Rayleigh distribution, while the FSO link follows a generalized $M{\acute{a}}laga$ (M) distribution. Considering the fixed gain amplify-and-forward (AF) relay and misalignment errors, novel expressions for the outage probability (OP), average bit error rate (ABER) and average capacity are derived. Numerical results show that atmospheric turbulence and misalignment errors can seriously impair the system performance, and the hybrid RF/FSO communication system using SIMO-RF links can greatly improve system performance. We also analyze system performance under different types of modulation schemes. Numerical results are verified by Monte Carlo simulations.

• ETRI Journal
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• v.35 no.5
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• pp.786-796
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• 2013

In this paper, we propose a hybrid time-division multiplexing and dense wavelength-division multiplexing scheme to implement a cost-effective and scalable long-reach optical access network (LR-OAN). Our main objectives are to increase fiber plant utilization, handle upstream and downstream flow through the same input/output port, extend the reach, and increase the splitting ratio. To this end, we propose the use of an arrayed waveguide grating (AWG) and an erbium-doped fiber amplifier (EDFA) in one configuration. AWG is employed to achieve the first and second objectives, while EDFA is used to achieve the third and fourth objectives. The performance of the proposed LR-OAN is verified using the Optisystem and Matlab software packages under bit error rate constraints and two different approaches (multifiber and single-fiber). Although the single-fiber approach offers a more cost-effective solution because service is provided to each zone via a common fiber, it imposes additional losses, which leads to a reduction in the length of the feeder fiber from 20 km to 10 km.

• Journal of Communications and Networks
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• v.6 no.3
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• pp.269-279
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• 2004

A new online multi-layer integrated routing (MLIR) scheme that combines IP (electrical) layer routing with WDM (optical) layer routing is investigated. It is a highly efficient and cost-effective routing scheme viable for the next generation integrated optical Internet. A new simplified weighted graph model for the integrated optical Internet consisted of optical routers with multi-granularity optical-electrical hybrid switching capability is firstly proposed. Then, based on the proposed graph model, we develop an online integrated routing scheme called differentiated weighted fair algorithm (DWFA) employing adaptive admission control (routing) strategies with the motivation of service/bandwidth differentiation, which can jointly solve multi-layer routing problem by simply applying the minimal weighted path computation algorithm. The major objective of DWFA is fourfold: 1) Quality of service (QoS) routing for traffic requests with various priorities; 2) blocking fairness for traffic requests with various bandwidth granularities; 3) adaptive routing according to the policy parameters from service provider; 4) lower computational complexity. Simulation results show that DWFA performs better than traditional overlay routing schemes such as optical-first-routing (OFR) and electrical-first-routing (EFR), in terms of traffic blocking ratio, traffic blocking fairness, average traffic logical hop counts, and global network resource utilization. It has been proved that the DWFA is a simple, comprehensive, and practical scheme of integrated routing in optical Internet for service providers.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.12
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• pp.37-44
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• 2005

This paper proposes a hybrid scheme for dynamic bandwidth allocation(DBA) in Ethernet passive optical network(EPON), which combines advantages of adaptive cycle and constant cycle-based schemes. The proposed scheme is based on IPACT scheme, but it operates as adaptive cycle or constant cycle mode according to the queue status of optical line terminal(OLT) for downstream transmission. Simulation results showed that the proposed scheme could achieve a similar throughput in downstream transmission to a constant cycle-based DBA scheme, while producing a similar delay performance to the IPACT scheme in upstream transmission.