Tatsuya Shiragaki

Optical cross-connect system incorporated with newly developed operation and management system

The optical cross-connect (OXC) system described in this paper increases the operation flexibility and reliability of the trunk-line optical networks used for data communication. It features an OXC node comprised of a photonic switching network and a conventional electric switching network that are connected hierarchically. The operation and management scheme proposed for this OXC system uses the concept of an optical path and an optical section. The OXC system allows hitless network reconfiguration by switching the photonic switches gradually and without interference effects. An experimental OXC network showed that a broken optical path is restored, by rerouting, within 50 ms. Experiments using a LiNbO/sub 3/ 8/spl times/8 photonic switch matrix also showed that the OXC system provides photonic hitless switching. These results confirm the feasibility of flexibly reconfigurable and fast-restorable OXC systems.

Network resource advantages of bidirectional wavelength-path switched ring

Wavelength-division-multiplexing (WDM) transport ring-network architectures analogous to conventional time-division multiplexing systems are disadvantageous in that they require either an increase in the necessary number of wavelengths, or long optical-transmission brought about by loop-back, thus raising costs. We have studied a transport WDM ring network in which the switching unit is wavelength and the standby resources are shared. Its advantages are confirmed by evaluation of the necessary number of wavelengths, the maximum circumference for a transparent ring, and the number of 3R-regenerators (3R: reshaping, regeneration, and retiming) for a large-sized opaque ring network.

Optimum protection architecture for reliable dense-WDM lightwave networks

This paper examines reliable and economical wavelength-division-multiplexed trunk-network protection architectures. Protection architectures for lightwave networks are classified as path/link switching type or dedicated/shared standby-resources type. The required number of optical links for each protection-architecture is calculated and compared in terms of the number of wavelengths, demand patterns, and several network topologies. The results show that the path-dedicated protection architecture, which enables fast protection, is pretty cost-effective for a typical regional network when the number of wavelengths is more than ten. Dense-WDM technologies will replace the economical and reliable protection-architecture from the ordinary link-shared protection to the path-dedicated protection.

Wavelength-division add/drop multiplexer using a single wavelength-filter and back-reflector switches

Summary form only given. The increase of the channels in wavelength-division multiplexing (WDM) in optical systems will make possible reconfigurable and transparent WDM networks, such as ring networks with wavelength-division add-drop multiplexer (WD-ADM). The most crucial issue for the WD-ADM system is the limitation of the cascaded-node count caused by passband-frequency misalignment of wavelength multiplexers/demultiplexers. For example, cascadability performance of an arrayed waveguide grating (AWG) spaced at 100-GHz interval is practically limited to several spans. In this paper, we propose a novel WD-ADM configuration using a single AWG and back-reflecting-type Er/sup 3+/-doped fiber amplifier (EDFA) gate switches, which improves the allowable cascaded-node count. The feasibility of the proposed WD-ADM configuration has been confirmed through experiments, and the cascadability of nodes has been estimated.

Reduction of crosstalk in a photonic space-division switching network employing traveling wave amplifiers and automatic power control

Because of optical loss variations through different connection paths in LiNbO/sub 3/ switch matrices, optical crosstalk in a photonic space division switching network will be enhanced. This work theoretically investigates the power penalty due to optical crosstalk in a 128 line photonic space division switching network which employs loss compensating semiconductor amplifiers, and experimentally confirms the suppression of power penalty by employing an automatic power control (APC) scheme. Experiments have shown the successful operation of an APC system in keeping a constant optical power level throughout the system and the negligible power penalty values obtained agree with a calculated model.<<ETX>>

Reduction of crosstalk in a photonic space division switching network employing traveling wave amplifiers and automatic power control

Because of optical loss variations through different connection paths in LiNbO/sub 3/ switch matrices, optical crosstalk in a photonic space division switching network will be enhanced. This work theoretically investigates the power penalty due to optical crosstalk in a 128 line photonic space division switching network which employs loss compensating semiconductor amplifiers, and experimentally confirms the suppression of power penalty by employing an automatic power control (APC) scheme. Experiments have shown the successful operation of an APC system in keeping a constant optical power level throughout the system and the negligible power penalty values obtained agree with a calculated model. >