Abstract—Translucent WDM networks use a set of sparsely but strategically placed 2R or/and 3R regenerators to overcome physical impairments and wavelength collision introduced by fully transparent networks. In this paper, we concentrate on the study of control architectures and management approaches for connection establishment in translucent networks. A hybrid OCP (optical control plane) has been proposed, which needs the extensions of both routing and signaling protocol. In hybrid OCP, we combine the best features of routing based information updating and signaling based data collection and path evaluation, in order to achieve better performance. Simulations are conducted to compare hybrid OCP with two existing control architectures: signaling based OCP and routing based OCP. Numerical results show that hybrid OCP keeps a lower blocking probability than the other approaches, and also minimize the stability and scalability problems under various traffic conditions. Index Terms—DWDM, GMPLS, optical control plane, physical impairments, translucent optical network I. INTRODUCTION Optical transport is evolving from traditional opaque networks toward all-optical transparent networks. The absence of electronic regenerators in transparent WDM networks contributes significantly to reduce the overall network cost. However, physical impairments (such as ASE noise, PMD, crosstalk, nonlinear effects, etc.) will accumulate along the transparent lightpath, which may degrade optical signal quality in long-haul transmission systems and make the data unrecognizable at the receiver. Thus, the transmission reach of signals in transparent networks is limited [1]. Translucent WDM networks use a set of sparsely but strategically placed 2R or/and 3R regenerators to overcome physical impairments and wavelength collision introduced by fully transparent networks [2]. Rather than purely electronic or purely optical, a translucent WDM network is a compromise between all-electronic switching and all-optical switching [1]. Extensive studies indicate that even if only a few regenerators This work is supported by 863 program (2006AA01Z244), BUPT Innovation fund, NSFC project (60772022), NCET program (NCET-05-0112), PCSIRT program (IRT0609) and 111 Project (B07005) of China. All authors are with Key Laboratory of Optical Communication and Lightwave Technologies, Ministry of Education, Beijing University of Posts and Telecommunications, Beijing, P.R.China (e-mail: hechen0001@gmail.com ; lgr24@bupt.edu.cn ; wyg@bupt.edu.cn ). are employed, translucent networks can achieve elegant service provisioning performance close to all opaque networks, but much better than that of fully transparent networks [3-5]. In [1], S. Gangxiang presents the survey of recent research advances in planning and operation of translucent networks. But few studies concentrate on translucent connection establishment and management approaches in real WDM networks. In ASON networks, Generalized Multi-Protocol Label Switching (GMPLS) is an implementation of the control plane (CP) to facilitate the establishment of Label Switched Paths (LSPs), involving signaling, routing, and resource management functions and protocols. But standard GMPLS does not take into account the physical impairments and regenerator employment of real optical networks, and also need some extensions to support the automatic setup/teardown of translucent connections. The extensions involve: 1) Data (resources related data and physical data) collection or updating. Resource related data includes the wavelengths state of the links and the resource (such as 3R regenerators, transmitters and receivers) state of the nodes, where physical data include the physical impairments (PI) introduced by the links/nodes. 2) Lightpath quality estimation (LQE). To guarantee the quality of signal, the accumulated physical impairments of each transparent segment on translucent path must be estimated and compliant with an acceptable range of required QOS. 3) Dynamic translucent path routing and resource assignment. In previous study [6-8], Routing based OCP and signaling based OCP have been proposed and compared for impairment-aware transparent networks. In this article, we extend them for translucent WDM networks. The first approach (routing based) introduces resource related (RR) data and physical impairments into the routing protocol i.e. OSPF-TE. By flooding Link & Node State Advertisements (LNSAs), all the nodes update their Global RR and PI Database (G-RRD & G-PID) in addition to the basic TE database (B-TED) which gives them a complete view of the whole network. Considering LQE and regeneration allocation strategy, the source node can find the proper translucent route for a connection request while standard RSVP-TE signaling is used for translucent path establishment. The second approach (signaling based) extends RSVP-TE protocol instead. Each node can select a route based on standard OSPF-TE without knowledge of G-RRD and G-PID. Then the availability of the calculated optical path is estimated and 3R regenerators are deployed on a hop-by-hop A Hybrid Control Architecture for Connection Management in Translucent WDM Networks Lei Wang, Jie Zhang, Guanjun Gao, Yongjun Liu, Xiuzhong Chen and Wanyi Gu, Member, IEEE This full text paper was peer reviewed at the direction of IEEE Communications Society subject matter experts for publication in the IEEE "GLOBECOM" 2008 proceedings. 978-1-4244-2324-8/08/$25.00 © 2008 IEEE.