Most major Japanese companies involved in lightwave devices have had strong optical data-link (ODL) product lines for many years. Beginning with AlGaAs emitters, they moved quickly into InGaAsP technology because of improved reliability and lower fiber attenuation. Applications include point-to-point interconnections within ATM switches and high-speed transmission equipment, between computer frames and video file servers, for board-to-board and intraboard applications, for LANs, automotive applications, consumer electronics, etc. (Optical fiber cables - mostly low-bandwidth POF - are widely available in Japanese electronics stores for interconnecting digital consumer products.)

Data links that operate at 155 Mbit/s, 622 Mbit/s, and 2.5 Gbit/s have obvious telecommunications applications, particularly for broadband access. Oki is developing a low-cost 12-channel 155 Mbit/s link for board-to-board interconnection for a subscriber-network application, with a target price of $20/channel. NEC is developing LED array modules to use with 63/125 Ám fiber for interconnecting ATM equipment at 155 Mbit/s. Toshiba has 1 Gbit/s data links in production and 2.5 Gbit/s links under development. Panel hosts at Toshiba commented that one of their 1300 nm high-speed data links is suitable for FTTH applications. Sumitomo also is developing data links that operate up to 2.5 Gbit/s.

Fiber-distributed data interface (FDDI) is an important emerging market. Used for local-area networking, FDDI provides 100 Mbit/s connectivity to desktop equipment over multimode fiber, but it has not met its early market forecasts because of high prices. This has led to a competing product, copper-distributed data interface (CDDI), which uses copper pair and transmits 52 Mbit/s, for example, using spectrally efficient modulation formats such as discrete multitone (DMT) or 16-CAP (carrierless amplitude and phase). Nevertheless, FDDI offers noise immunity and other advantages of fiber, and it continues to increase in popularity. Sumitomo manufactures 1.3 Ám data links that sell for $100 per transceiver, and it claims to have 30% of the U.S. market.

NEC has a program aimed at using the new GI-POF with both 650 nm lasers and 570 nm LEDs. The company is also interested in combining 980 nm lasers with plastic-clad silica (PCS) fibers for data-link applications, and it is developing a 980 nm VCSEL for this application. Also for this application, NEC is investigating array devices, including VCSEL arrays, for byte-parallel (or ribbon-wide) transmission.

With regard to data links, both U.S. and Japanese manufacturers have similar products up to as high a bit rate as 1 Gbit/s.

Published: February 1996; WTEC Hyper-Librarian