This paper discusses the innovation in network architectures, and optical transport, that enables metropolitan networks to cost-effectively scale to hundreds Gb/s of capacity, and to hundreds km of reach, and to also meet the diverse service needs of enterprise and residential applications. A converged metro network, where Ethernet/IP services, and traditional TDM traffic operate over an intelligent WDM transport layer is increasingly becoming the most attractive architecture addressing the primary need of network operators for significantly improved capital and operational network cost. At the same time, this converged network has to leverage advanced technology, and introduce intelligence in order to significantly improve the deployment and manageability of WDM transport. The most important system advancements and the associated technology innovations that enhance the cost-effectiveness of metropolitan optical networks are being reviewed.
This paper evaluates the network architectures, the innovation in optical (WDM) system design, and the related transport technologies that have enabled metropolitan networks to scale to hundreds Gb/s of capacity, and to hundreds km of reach, meeting the diverse service needs of enterprise and residential applications, while maintaining cost lower than traditional long-haul optical transport. The analysis have lead to the development of a multi-service WDM system scalable to more than 300 Gb/s, and 500 km, exceeding the previous related demonstrations in reach and network (OADM) complexity. The most important performance achievements are summarized. The paper finally discusses future important technologies that hold promise to further enhance the cost-effectiveness of metropolitan optical systems.
The physical properties of photopolymer grating formation are, for the first time, investigated elaborately with respect to I, and (Lambda) . The dynamics of holographic recording with constant exposure energy (15mJ/cm2), are evaluated for a wide range of different I (mW/cm2 - W/cm2), and for a few typical (Lambda) (0.5 - 3.5 micrometer), in a material utilizing cationing-ring-opening polymerization (Polaroid CROP ULSH-500B). Diffusion was evaluated to limit the photo- initiated recording sensitivity at high I(greater than W/cm2 approximately (Lambda) -2). At the same time, however, the significant post-exposure grating development observed for diffusion limited recordings, was identified to allow eventually for equally high sensitive final gratings (approximately 3 - 5 cm/mJ) without reciprocity, or diffusion limitations. Based on these observations, a new physical model was developed that describes more accurately holographic recording utilizing photo-initiated polymerization, and accounts successfully for the observed physical properties of grating formation.
We evaluate the physical properties of volume holographic recording in photopolymer that allow for high performance nonvolatile digital data storage. We identified efficient volume grating formation for photoinitiated cationic-ring- opening polymerization that utilizes unrestricted monomer diffusive transport contributions in the grating development process during and after exposure.
Volume holographic recording of information is an attractive solution for the next generation of digital storage systems, for the ability to optically record and retrieve, independently, multiple superimposed holograms, transferring in parallel the corresponding page-formated digital data representations.
KEYWORDS: Diffraction gratings, Holography, Polymerization, Diffusion, Polymers, Diffraction, Digital holography, Data storage, Holographic data storage systems, Digital recording
We investigated compositional volume grating formation in the Polaroid medium that utilizes the cationic-ring-opening photoinitiated polymerization process, and compared our conclusions with the current physical model describing polymer holographic recording. We identified the effects of diffusion and polymerization during illumination, as well as significant postexposure grating development. Holographic recording in this medium allows for final strong gratings with high recording sensitivity (S approximately 2 cm/mJ), that were not limited at the higher recording intensities (I less than or equal to 250 mW/cm2) corresponding to photon (exposure) limited recording. The results of the present analysis allow for more comprehensive physical description of grating formation in the photoinitiated CROP process, and evaluation of the polymer recording process in a nonvolatile holographic storage system.
KEYWORDS: Diffraction gratings, Scattering, Signal to noise ratio, Digital holography, Holography, Polymers, Interference (communication), Diffraction, Statistical analysis, Data storage
The performance of holographic storage in photopolymer recording media gets limited by compositional volume grating distortions, arising primarily due to postrecording anisotropic medium dimension changes. We evaluate the polymer grating distortions, and the corresponding diffraction efficiency fluctuations, as noise in the holographic digital system. The analysis suggests the importance of the distortion induced grating strength fluctuations relative to optical scattering from the system performance, and encoding, characteristics at different grating distortion regimes.
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