FTTx stimulates tri-speed Ethernet standard

A major reason for Ethernet's unparalleled success in customer-owned networks has been support of higher speeds as network traffic increases. Extending the performance of the original 10-Mbit/sec Ethernet are 100-Mbit/sec Fast Ethernet (FE), Gigabit Ethernet (GbE), and 10-GbE. 100-Mbit/sec FE as originally introduced for unshielded twisted-pair copper was not backward-compatible with 10-Mbit/sec Ethernet. Today, copper Ethernet products support 10, 100, and 1,000 Mbits/sec, enabling smooth migration paths.

As networks move to higher speeds, the need to support migration over fiber with a flexible standard has likewise increased. Until ratification of TIA/EIA-785, fiber Ethernet LAN equipment supported only single speeds. TIA/EIA-785 was the first fiber Ethernet standard to support multiple 10- and 100-Mbit/sec speeds, with auto-negotiation, at the economical 850-nm short wavelength. Parallel detection ensures compatibility with legacy 10-Mbit/sec products.

Interest in higher-multispeed fiber Ethernet for customer-owned networks was first voiced by users in a BICSI survey conducted in late 2001. In response, TIA FO-4.2.2 is developing a new tri-speed fiber Ethernet standard to support 10/100/1,000-Mbit/sec operation for both customer-owned and public networks. It is expected that both short- and long-wavelength physical medium-dependent layer (PMD) specifications will be developed. As with the 10/100-Mbit/sec TIA/EIA-785 standard, the economical 850-nm PMD will specify operation over multimode fiber.

In the public network, service providers desire to offer economical, rate-controlled Ethernet directly to customers. Carrier class Ethernet is estimated to cost less than 25% of traditional SONET implementations. To support greater distances, the standard is expected to include PMDs for singlemode operation at 1310 and 1550 nm.

In extending the fiber auto-negotiating Ethernet migration path beyond the 10/100-Mbit/sec capabilities introduced with TIA/EIA-785, the new tri-speed standard should meet the requirements of many fiber to the x (FTTx) applications, including fiber to the business, home, desk, and factory floor.

John Struhar is chairman of the TIA Fiber Optics LAN Section and distinguished member of technical staff at OFS (Norcross, GA). He can be reached at 770-798-3281 or jstruhar@ofsoptics.com.

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