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In this paper, we consider performance improvements for a sparse groomed wavelength routed optical wavelength division multiplexed (WDM) network. In such networks, the wavelength capacity per channel can be as high as 40 Gbps whereas the individual session requests can be much lower. Traffic grooming, that multiplexes several sessions on a wavelength, is a widely studied technique to reduce the effects of this capacity mismatch. In this paper, we consider an electronic traffic groomed network that consists of SONET/SDH groomers at the core optical cross connect (OXC) nodes. Since these groomers are expensive, reducing the number of groomers needed is an important design goal. A sparse groomed network is defined as one where only a subset of the core network nodes possess grooming capability in addition to optical switching; other nodes only possess optical switching and optical add/drop capabilities. In order to improve the overall blocking probability, we present a mechanism for reserving wavelengths between the grooming nodes in a network. The performance of the mechanism is studied using discrete event simulation techniques for various topologies and system parameters. The results show that when we reserve enough wavelengths for groomed traffic, the performance of the network is improved by up to 100% and up to 76% for ARPANET and NSFNET topologies respectively.