Developing leading-edge fiber-optic network link standards

Hewlett-Packard Journal, Dec, 1997 by David G. Cunningham, Delon C. Hanson, Mark C. Nowell, C. Steven Joiner

Advances in fiber-optic network technology within Hewlett-Packard are achieved by close cooperation between Hewlett-Packard Laboratories (HPL) and Hewlett-Packard's Communications Semiconductor Solutions Division (CSSD). This paper explores the interaction between HPL and CSSD for the advancement of high-speed LAN standards, particularly in the ATM Forum and IEEE 802.3z (Gbit/s Ethernet). Details of major technical contributions to 622-Mbit/s ATM and Gbit/s Ethernet specifications are presented.

Standardization has created a global fiber-optic LAN market in which Hewlett-Packard competes. However, successful open LAN standards are developed by consensus. Consensus is fundamental to the standardization process, since it ensures that the technological advances embodied in a final standard will be implemented by a number of vendors. In addition, standardization gives customers confidence that LAN products will not originate from a single source with corresponding higher prices. Given the need for consensus, it is important that Hewlett-Packard continuously participate in LAN standards development so that the company remains aware of current industry and future standards requirements. This understanding is a very important input into the strategic planning process for the HP Communications Semiconductor Solutions Division (CSSD) and Hewlett-Packard Laboratories (HPL).

Consensus-based standards make it impossible for any company to dominate the global optical-fiber LAN market. However, a long-term collaboration between HPL and CSSD has enabled Hewlett-Packard to be a market leader in high-speed optical-fiber LANs. Responsibility for developing future business and standards strategy is jointly owned by CSSD's strategic Pathfinders and HPL. CSSD and HPL engage the standardization process as early as possible. Involvement in embryonic standards provides valuable insight into the capabilities and needs of Hewlett-Packard's competitors, partners, and customers. Based on this insight we adapt our standards and research strategy so that there is maximum likelihood of it being accepted by consensus-driven standards bodies. Actively influencing emergent standards ensures that a good return is achieved from Hewlett-Packard's investment in research and development. Obviously, this is a long-term commitment involving the continuous seeding of the Hewlett-Packard Laboratories research agenda many years in advance of emerging standards or customer needs.

Recently, two major high-data-rate fiber-optic LAN standards have emerged: 622-Mbit/s (OC-12) Asynchronous Transfer Mode (ATM) and Gbit/s Ethernet. Building wiring standards require optical fiber transmission over 500 m of 62.5/125-[Mu]m (core/cladding diameter) multimode fiber (62MMF) for backbone links. This building wiring standards requirement determines the choice of transceiver technology, as illustrated in Figure 1. The ATM Forum, which requires a 622-Mbit/s line rate, considered long-wavelength LEDs and short-wavelength laser diodes. VCSELs (vertical-cavity surface emitting lasers) operating near wavelengths of 980 nm were also discussed in the context of Gbit/s ATM links. The Gbit/s Ethernet standards committee considered short-wavelength laser diodes and long-wavelength laser diodes. CSSD and HPL made major technical contributions to both standards, which led to the inclusion of 1300-nm LEDs in the OC-12 ATM Forum specification and 1300-nm laser diodes in the Gbit/s Ethernet specification.

This paper will provide insight into the long-term collaboration between CSSD and Hewlett-Packard Laboratories in the area of fiber-optic LAN standards. The collaboration will be explored through the chronology of Hewlett-Packard's involvement in the development of recent LAN standards, particularly in the ATM Forum and IEEE 802.3z (Gigabit/s Ethernet).

Wiring Link Length and Transceiver Technology

Budding wiring is a large capital investment usually amortized over approximately 15 years. To protect this investment, International Standards Organization (ISO) building wiring system standard ISO/IEC 11801 specifies cabling architectures, link lengths, and type. Historically, fiber-optic backbones for LANs are developed to support the link length requirements defined in ISO/IEC 11801. These requirements evolved out of the recognized need in the mid-1980s to achieve a more unified approach to developing and installing LANs. As illustrated in Figure 2, a key aspect of this building wiring standard is the definition of link lengths: 100 m horizontal from hubs to the desktop (90 m of cable plus up to 10 m for patch cords), 500 m for building backbone, and 2 km for campus backbone. These link length requirements dictate the choices of fiber-optic cable and transceiver technology as a function of data rate. In particular, because of its suitability for use with low-cost light-emitting diode (LED) transceivers, the installed base of optical fiber is predominantly 62MMF in both the U.S.A. and Europe. Transceiver vendors and fiber-optic LAN standards must develop transceiver technology that operates in harmony with the building wiring standards to protect the capital investment of both LAN users and LAN equipment suppliers.