In practical multi-granularity WDM optical networks, optical signals will be degraded due to impairments mainly
introduced by a number of multi-granularity optical cross-connects (MG-OXC) and fiber links. Even worse,
transmission impairments will make the bit-error rate to be unacceptable. We investigate the impact of transmission
impairments on optical signal quality in multi-granularity WDM optical networks. A novel dynamic impairment-aware
RWA algorithm is proposed based on the presented transmission impairments model. We also evaluate the proposed
algorithm in the serial cascaded MG-OXCs network and the interconnecting MG-OXCs network by simulations.
Multi-granularity optical cross-connects (MG-OXC) is proposed as a promising technique to reduce the cost of the optical nodes in the wavelength division multiplexing (WDM) optical networks. In this paper, we use the on-line Maximize the Number of Waveband Route (MNWR) algorithm to evaluate the performance and optimize the design of multi-granularity optical WDM networks based on two different MG-OXCs: the serial MG-OXCs and the interconnecting MG-OXCs. The numerical results show that our optimal design can significantly reduce the network complexity and the blocking probability.
In this paper, a tunable single-frequency fiber laser is designed. For narrow linewidth and single frequency
operation, a length of 2.75m unpumped EDF as a saturable absorber is used. The FBG combined with the unpumped
EDF provides narrow frequency selection. Counter propagating beams in the unpumped EDF form a standing wave
that results in periodic spatial hole burning. This creates a narrower bandwidth absorption grating than the FBG. The
output laser wavelength can be changed from 1530nm to 1570nm by the FBG. The 3dB spectrum width of output
laser is 0.08nm and the side mode suppression ratio is 55dB. The maximum output power exceeds 12mW, and the
stability is less than ±0.005dB. A nice single-frequency laser is observed. From the relationship of the pump power
and output power, it is obvious that the optical bistability switchable phenomena is showed in output characteristics.
The bistability switchable phenomena is caused by the saturable absorber in the ring cavity. A 10Gb/s codes rate is
used in the fiber laser transmission experiment. The high speed optical signal is transmitted in long distance without
regeneration. The eye diagrams of optical transmission are measured, the performance of long haul transmission
with high speed modulation is perfect.
In this paper, a short polarization-maintaining Er:Yb co-doped fiber laser is experimented. A pair of FBGs are
written in the Er:Yb co-doped sensitive fiber using UV beams. A 976nm pumping laser diode is used, and output
wavelength is selected by two FBGs. The PM Er:Yb co-doped fiber is used to main the orthogonal polarizations SM
lasing stability. The SM operation in each wavelength has been verified. On the basis of previous short cavity fiber,
a simple DBR dual wavelength fiber laser array has been designed and experimented. Two sections of short Er:Yb
co-doped fiber cavities are pumped by a 976nm LD simultaneously. The pump laser is splitted to pump each Er:Yb
co-doped fiber. It used a WDM coupler at 1550nm to connect the output port of two DBR fiber laser, an isolator is
spliced to the common arm of the WDM and used as the output port. The dual wavelength spacing is 0.31nm. The
output power reaches 6mW with the optical signal to noise ratio of greater than 30dB. A 12.5Gb/s codes rate is used
in the fiber laser transmission experiment. A nice optical eye diagram is recieved after long distance single-mode
communications fiber transmission.
Two novel multi-granularity optical cross-connect (MG-OXC) architectures for dense wavelength division multiplexing (DWDM) networks are proposed to realize transparent waveband switching, and hence to reduce the switching and transmission costs. The performances of the two architectures are studied and compared in detail. The functionality of the proposed interconnecting architecture is investigated for a 10-Gb/s WDM system.
Waveband switching (WBS) is proposed as a promising technique to reduce the number of switching ports, which could translate to the switching fabric size and cost of the nodes in the dense wavelength division multiplexing (DWDM) network. We propose a routing and wavelength/waveband (RWA) heuristic algorithm, called Maximize the Number of Waveband Route (MNWR) for the dynamic arriving traffic demands in the multi-granularity WBS optical network. We study the performance of various MG-OXC architectures including the serial three-stage MG-OXC and the interconnecting three-stage MG-OXC proposed by our group employing the on-line MNWR algorithm. Simulation results indicate that the interconnecting three-stage MG-OXC outperforms the serial three-stage architecture in terms of blocking performance for dynamic requests.
We study the design issues of a node in multi-granularity all-optic network based on a proposed dynamic multigranularity including coarse granularity (i.e., fiber and band) and fine granularity (i.e., wavelength) traffic model. An optimization design plan is proposed by analyzing the associated parameters of MG-OXC architecture in detail and optimizing the configuration of them. The proposed optimization design rules can significantly reduce the node complexity and improve the blocking performance of arriving requests, which lead to smaller device size and lower cost in all-optical networks.
A translucent multicasting scheme based on sparsely placed signal re-generable translucent multicasting capable optical cross connect (tMC-OXC) nodes is proposed to provide signal-quality guaranteed multicasting services. We propose a tMC-OXC architecture capable of transparent unicasting and electronic multicasting. The electronic multicasting devices are also used to regenerate the impaired signals. A regeneration weight based MC-OXC nodes placement
strategy is designed to construct the translucent network. We propose two multicasting tree construction algorithms to evaluate the performance of the proposed translucent network, where the selected MC-OXC nodes serve as core nodes (we call them hub nodes). Our study shows that no more than 30% nodes need to be equipped with electronic multicasting and electronic 3R regeneration capability, having more than 30% nodes with regeneration capability only slightly enhances the network performance.
The emerging broadband real-time streams applications require the supporting networks to provide multicasting communication at optical layer. The multicasting capable optical cross-connect (MC-OXCs) is the necessary device to implement multicasting at optical layer. The functional building blocks for MC-OXC are light splitters, which can be space splitters or multiwavelength converters (frequency splitters). The space splitter has no wavelength conversion ability, while the frequency splitter has limited fanout, decreased optical signal-to-noise ratio and also is expensive. We proposed a tradeoff architecture called joint multicasting capable optical cross-connect (jMC-OXC) integrating both space splitters and frequency splitters in our previous work. This paper further studies the network performance in terms of member blocking ratio for the jMC-OXC architecture. Three simulation schemes are designed and the results show that the network performance of the jMC-OXCs with limited frequency splitters can obtain a close performance to that with full frequency splitters.
We study the optimization issues of ring networks employing novel parallel multi-granularity hierarchical OADMs. In particular, we attempt to minimize the number of control elements for the off-line case. We present an integer linear programming formulation to obtain the lower bound in optimization, and propose an efficient heuristic algorithm called Global Bandwidth Resource Assignment (GBRA) that is suitable for the design of large-scale OADM networks.
From element automatic control view, we propose a configuration algorithm for three-level cross-connects in data plane to handle with bypass, grooming and local add/drop traffic of fiber-level, band-level and wavelength-level by a abstract bipartite graph of MG-OXC and bandwidth utilization spectra graph. The configuration algorithm is evaluated by computer simulation as well as validated by experiment on our flexible Multi-functional Optical Switching Testbed (MOST).
To solve the scalability and flexibility issue in current optical network testbeds, a Multi-functional Optical Switching Testbed (MOST) has been built. Benefiting from design of modular hardware and layered software, network experiments of scalability and complicated node architecture can be made based on it. The hardware and software structure of the MOST system is explicitly analyzed in the article and demonstrations of a 12-node ASON and shared wavelength conversion ASON on MOST are also reported.
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