Gary Landry

VCSEL-Based Interconnects for Current and Future Data Centers

The vast majority of optical links within the data center are based on vertical cavity surface emitting lasers (VCSELs) operating at 850 nm over multimode optical fiber. Deployable links have evolved in speed from 1 Gb/s in 1996 to 28 Gb/s in 2014. Serial data links at 40 and 56 Gb/s are now under development and place even more demand on the VCSEL and photodiodes. In this paper, we present the characteristics of VCSELs and photodiodes used in current generation 28 Gb/s links and present several methods to extend link distances using more advanced data encoding schemes. Finally, we will present results on wavelength division multiplexing on multimode optical fiber that demonstrate 40 Gb/s Ethernet connections up to 300 m on duplex OM3 optical fiber, and present results on fiber optimized for modal bandwidth in the 850 to 980 nm range.

A 56.1Gb/s NRZ modulated 850nm VCSEL-based optical link

We report a directly modulated 850nm VCSEL-based optical link operating at 56.1Gb/s (BER <; 1E-12). This is the highest modulation rate for a VCSEL-based link of any wavelength. An open eye is obtained at 60Gb/s.

The next generation of high speed VCSELs at Finisar

Commercial demand for optical transceivers operating at 14Gbps is now a reality. It is further expected that communications standards utilizing 850nm VCSELs at speeds up to 28Gbps will be ratified in the near future. We report on the development and productization of 850nm VCSELs for several applications, including high speed (both 14Gbps and 28Gbps) operation to support the continued fulfillment of data communication demand.

Reliability of VCSELs for >25Gb/s

The next individual-channel VCSEL (Vertical Cavity Surface Emitting Laser) node for data communications is 25 Gbps or higher. Providing the required reliability becomes ever more challenging as the speeds increase, but possible with proper design.

The range of VCSEL wearout reliability acceleration behavior and its effects on applications

For nearly twenty years most models of VCSEL wearout reliability have incorporated Arrhenius activation energy near 0.7 eV, usually with a modest current exponent in addition. As VCSEL production extends into more wavelength, power, and speed regimes new active regions, mirror designs, and growth conditions have become necessary. Even at more traditional VCSEL 850-nm wavelengths instances of very different reliability acceleration factors have arisen. In some cases these have profound effects on the expected reliability under normal use conditions, resulting in wearout lifetimes that can vary more than an order of magnitude. These differences enable the extension of VCSELs in communications applications to even greater speeds with reliability equal to or even greater than the previous lowerspeed devices. This paper discusses some of the new applications, different wearout behaviors, and their implications in real-life operation. The effect of different acceleration behaviors on reliability testing is also addressed.

Emerging VCSEL technologies at Finisar

In this paper we will discuss recent results on high speed VCSELs targeted for the emerging 16GFC (Fibre Channel) standard as well as the now forming 25Gbps PCI express standard. Significant challenges in designing for reliability and speed have been overcome to demonstrate VCSELs with bandwidth in excess of 20Gbps.