VCSELs Expand Communications Potential

Mary Hibbs-Brenner

It is fair to say that the introduction of vertical-cavity self-emitting laser (VCSEL) technology in the mid- to late 1990s enabled the widespread deployment of fiber optic links within an enterprise. The devices provided the right combination of high performance (greater than 1-Gb/s data rates), high reliability (lifetimes of millions of hours) and ease of packaging to enable the development of cost-effective transceivers for use in local- and storage-area network applications.

VCSELs increasingly support Internet applications, but they have only begun to exhibit their potential to transmit, sense and display information, and end users can expect many exciting developments within two or three years.

The big news this year will be the release of 10-Gb/s 850-nm VCSELs and companion receivers in the form of optical subassemblies. Intensive research at Honeywell has targeted the development of devices and packaging that robustly meet the required characteristics at 10-Gb/s transmission rates, while maintaining the high reliability standards demanded by the data communications industry. The optical subassembly product level provides value to the customer by ensuring that the product meets the encircled flux requirements that are specified by the IEEE-802.3ae standard (10 Gigabit Ethernet) for coupling into multimode fiber.

In the near future, end users also will see the deployment of long-wavelength VCSELs. The key characteristics required for application in fiber optic links have been demonstrated by a number of companies. These characteristics include light emission at wavelengths as long as 1338 nm, single-mode optical output power exceeding 0.5 mW over the -40 to 85 °C range and modulation rates up to 10 Gb/s. Honeywell engineers also expect to see the release of 1310-nm products in approximately six to 12 months, followed six to 12 months after that by 1550-nm VCSELs. These products will enable cost-effective performance in unique packages for longer-distance local- and storage-network applications, as well as for the access market.

The VCSEL opens up many possibilities for chip or wafer-scale integration, including the on-wafer integration of lenses.

Also on the horizon are shorter-wavelength (780 to 850 nm) single-mode products. Applications such as position translation and rotation, sensing, laser printing, oxygen sensing, atomic clocks and scanning will benefit from use of the coherence of the beam, low power dissipation and the unique and compact packaging enabled by the VCSEL. The key breakthroughs will include greater than 1-mW single-mode power with good reliability.

Finally, over the next two to three years, researchers will continue to make strides in the application of VCSELs to interconnects in applications such as the massive transfer of data from cabinet to cabinet within a room, from board to board within a cabinet, or from multichip module to multichip module on a board. The industry will see a wide array of products emerging from this technology development.

The ability to form integrated laser arrays on a single chip is unique to VCSELs, and it makes possible a solution that couldn’t have existed before: the parallel transfer of many high-speed signals. Early examples of these arrays have already found their way into systems in the form of parallel 1 x 12 VCSEL-based transceivers for connecting cabinet to cabinet. However, the vertically emitting format of the VCSEL opens up many possibilities for chip or wafer-scale integration (see figure). It is this possibility for sophisticated levels of integration that will enable the progressive penetration of optical interconnects into computing and networking systems.

Meet the author

Mary Hibbs-Brenner is director of R&D for Honeywell in Richardson, Texas.