VCSELs Expand Communications Potential
It is likely that most data that is transferred over the Internet encounters at least one VCSEL along the way.
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
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.
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