A fault management technique for the optical path network employing WDM is proposed. Fault management is divided into optical path fault management and equipment fault management. The former always monitors the optical path and guarantees optical path !zansp~rt performance through the network. The latter starts isolating the failed optical module after detecting the optical path failure. For robust optical path fault management, the bit mor rate @ER) of the optical signal should be monitored. Realized by the bit interleaved parity technique, this can create effective fault management.

Photonic networks that exploit the abundant optical bandwidth capability are needed to realize a truly effective B-ISDN. We have proposed two optical path schemes, the wavelength path (WP) scheme and the virtual wavelength path (W) scheme, wherein wavelength division multiplexing/frequency division multiplexing (WDM/FDM) technologies are employed in the path layer of the transport networks. Although wavelengths are precious resources in photonic networks, the number of wavelengths required for any network has never been evaluated because of the NPcompleteness of the wavelength assignment problem. In this paper, we propose heuristic optical path accommodation design algorithms that can minimize the wavelength requirements in the network. We also evaluate the wavelength requirements for large-scale and irregularly structured physical network topologies utilizing the proposed algorithms. Accordingly, we elucidate, for the first time, that the wavelength requirements for the WP and VWP schemes are almost the same regardless of physical network topologies and path demand distribution patterns.

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Key words: Optical network; optical path; wavelength division multiplexing; failure restoration. 30ISSN8756-662 1 /95/0007-0030

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