Ciena Expands Strategic Relationship with TELMEX.

LINTHICUM, Md. -- Ciena's CoreDirector Selected For Telefonos de Mexico's Nationwide Long-Distance Network; New Ethernet Modules Added to Existing CoreDirectors in Mexico City Metro Area Network

Ciena(R) Corporation (Nasdaq:CIEN), the network specialist, today announced an expansion of its role in the networking strategy of Telefonos de Mexico S.A. de C.V. (TELMEX) (NYSE:TMX), Mexico's largest telecommunications service provider. Ciena's CoreDirector(R) multiservice switching system has been selected for deployment across the TELMEX nationwide long-distance network.

Since 2002, Ciena's CoreDirector systems have been deployed in TELMEX's Mexico City network, one of the largest metropolitan area networks in the world. With this expansion, CoreDirector is now helping TELMEX's metro and long-distance networks by enabling a single, automated nationwide infrastructure.

"In our Mexico City network, Ciena's application-focused solution surpassed our expectations in its ability to prevent potential network failures, expedite service delivery and streamline overall operations," said Jaime Chico Pardo, chief executive officer at TELMEX.

CoreDirector's role in TELMEX's Mexico City metro network has also been expanded with the deployment of the platform's new Gigabit Ethernet Line Module to support native Ethernet connectivity. For Ciena, the new module is part of a growing set of data solutions on its CoreDirector platform that enables service providers to improve the quality and availability of data services aggregation and transport.

"During the last two years, Ciena and TELMEX have formed a strategic relationship around a shared network vision and the highest standards of excellence designed to enhance the service offerings throughout Mexico City," said Gary B. Smith, Ciena's president and CEO. "We are pleased to further expand our relationship with TELMEX as it demonstrates the versatility of our CoreDirector platform, and we look forward to continuing the success we've begun together."

CoreDirector, an integral part of Ciena's specialization in evolving network infrastructure for new applications and convergence, is the market-leading optical switch based on deployments worldwide with leading service providers. The platform is an intelligent, high-capacity switching system that incorporates the functionality of add-drop multiplexers (ADMs), multiservice provisioning platforms (MSPPs), digital and optical cross-connects plus Layer 2 functionality in a single system that automates network operations and improves network reliability.

ABOUT CIENA

Ciena Corporation is the network specialist, focused on expanding the possibilities for its customers' networks while reducing their cost of ownership. The company's systems, software and services target and cure specific network pain points so that telcos, cable operators, governments and enterprises can best exploit the new applications that are driving their businesses forward. For more information, visit www.ciena.com.

NOTE TO INVESTORS

This press release contains certain forward-looking statements based on current expectations, forecasts and assumptions that involve risks and uncertainties. These statements are based on information available to the Company as of the date hereof; and Ciena's actual results could differ materially from those stated or implied, due to risks and uncertainties associated with its business, which include the risk factors disclosed in its Report on Form 10-K, which Ciena filed with the Securities and Exchange Commission on December 9, 2004. Forward-looking statements include statements regarding Ciena's expectations, beliefs, intentions or strategies regarding the future and can be identified by forward-looking words such as "anticipate," "believe," "could," "estimate," "expect," "intend," "may," "should," "will," and "would" or similar words. Ciena assumes no obligation to update the information included in this press release, whether as a result of new information, future events or otherwise.