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VCSEL:
Vertical cavity surface emitting laser. A laser technology based on the methods of semiconductor manufacturing and packaging that enable high-volume manufacturing, lower-cost, and greater efficiencies.

Virtual LANs (VLANs):
A local area network with a definition that maps workstations on some other basis than geographic location (for example, by department, type of user, or primary application).

Virtual Private Networking (VPN):
A way to use a public telecommunication infrastructure, such as the Internet, to provide remote offices or individual users with secure access to their organization's network.

Virtual Telecommunications Access Method(VTAM):
An IBM application program interface (API) for communicating with telecommunication devices and their users. VTAM was the first IBM program to allow programmers to deal with devices as “logical units?without having to understand the details of line protocol and device operation. Prior to VTAM, programmers used IBM's Basic Telecommunications Access Method (BTAM) to communicate with devices that used the binary synchronous (BSC) and start-stop line protocols.

WAN PHY:
The optional PHY that includes a simple SONET framer and operates at a data rate compatible with the payload rate of OC-192c/SDH VC-4-64c.

WDM:
Wavelength division multiplexing: A means of data transmission that uses optical multiplexing to enable two or more wavelengths each with its own data source to share a common fiber optic medium.

WWDM:
Wide wavelength division multiplexing. A relatively low-cost WDM technology that uses wide spacing and uncooled optics.

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