KEYWORDS: Optical amplifiers, Multimode fibers, Optical filters, Receivers, Fiber amplifiers, Signal processing, Transponders, Digital signal processing, Cladding, Space division multiplexing
Space-division multiplexing enables fiber capacity increase beyond the limits imposed on single mode fibers by the
nonlinear Shannon limit. The capacity increase has to be implemented in a cost and energy efficient way in order to
enable a commercially viable solution. Optical amplifiers using multi mode fiber as an active medium achieve better
pump power efficiency than multi core fiber based amplifiers due to the higher density of modes. In addition, module
optimization approaches can be implemented to further reduce the cost and energy per transported bit. Mutli mode fibers
also posess a better capacity upgrade potential than multi core fibers due to the higher density of modes. Multiple input /
multiple output processing can be deployed for signal equalization at the receiver, if mode coupling occurs during
propagation along the link. An approach using adaptive optical filters for realization of the equalization function in the
optical domain enables low installation costs and capacity upgrade on demand by adding transponders for the individual
channels.
Spatial division multiplexing has been proposed for fiber capacity increase as an alternative to enhanced bandwidth
efficiency by higher order modulation or wider wavelength bands. The commercial viability of this approach will depend
strongly on the feasibility of cost and energy efficient optical amplification. Lumped erbium doped fiber and distributed
Raman amplifiers are the most promising candidates. Different approaches have been analyzed for the realization of
preamplifier and booster stages with different active fiber types. The multi mode fiber type was found to possess more
potential for cost and energy efficiency than the multi core fiber type.
In this paper we present a novel physical layer impairment (PLI) aware routing and wavelength assignment (RWA)
approach combined with PLI-aware regenerator placement. We consider the dominant linear and nonlinear signal quality
degrading effects in 10 Gb/s non-return to zero (NRZ) on-off keying (OOK) systems by analytical models for amplified
spontaneous emission noise (ASE), filter crosstalk, group-velocity dispersion (GVD) and polarization mode dispersion
(PMD) as well as cross-phase modulation (XPM) and four wave mixing (FWM). As a topology for our study we have
chosen the COST266 reference network, which is a pan-European meshed network with a total of 28 nodes and 41
(bidirectional) edges. For this network demands have been defined based on a population-based model. To facilitate
transmission over very long path lengths regenerator pools have been placed sparsely at certain nodes due to cost
considerations. The regenerator sites are selected based on a heuristic algorithm taking into account the physical effects
resulting in signal quality degradation. Due to the high cost of optical-electrical-optical (OEO) conversion as few
regenerators as possible are deployed. In our investigations we assumed a 1+1 path protection scheme in the optical
layer. The exact assessment of the signal quality based on the current traffic situation using our methods permits a
network performance (wavelength blocking probability) comparable to an opaque network with only a small number of
regenerators.
In this paper, WDM transmission experiments are discussed showing simultaneous compensation of
nonlinear effects and chromatic dispersion through optical phase conjugation (OPC). The performance of
OPC and DCF for chromatic dispersion compensation are compared in a wavelength division multiplexed
(WDM) transmission link with 50-GHz spaced 42.8-Gb/s RZ-DQPSK modulated channels. The feasible
transmission distance for a Q-factor ~10 dB is limited to approximately 5,000 km and 3,000 km for the OPC
and the DCF based configuration, respectively. When the Q-factor as a function of the transmission distance
is observed, at shorter distances, the Q-factor of the OPC based configuration is about 1.5 dB higher than
that of the DCF based transmission system. Up to 2,500-km transmission a linear decrease in Q is observed
for both configurations. After 2,500-km transmission, the Q-factor of the DCF based configuration deviates
from the linear decrease whereas the OPC based performance is virtually unaffected.
Due to the tenfold capacity increase of Ethernet from one generation to the next, 100 Gbps will be the straight forward next step after 10 Gbps. Demand can be predicted for the following years based on increasing internet data traffic and the lack of efficient packet based link aggregation mechanisms in the Ethernet protocol. Solutions have to be found for short haul intra-office and long haul inter-office interconnections of large routers. This contribution focuses on options for physical layer interfaces. Optical component aspects are discussed as well as transmission aspects. The selection of a suitable modulation format in combination with equalizer technologies opens a path towards robust transmission systems for this ultra-high datarate.
Artificial dielectric materials are dielectrics in which other dielectrics or conductors are embedded to achieve different, effective dielectric properties. In the experiment, transmission lines embedded with suspended GaAs crystallites were used. The effective dielectric constant was changing upon illuminating the strip-line with light.
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