Luke A. Graham

120-Gb/s VCSEL-based parallel-optical interconnect and custom 120-Gb/s testing station

A 120-Gb/s optical link (12 channels at 10 Gb/s/ch for both a transmitter and a receiver) has been demonstrated. The link operated at a bit-error rate of less than 10/sup -12/ with all channels operating and with a total fiber length of 316 m, which comprises 300 m of next-generation (OM-3) multimode fiber (MMF) plus 16 m of standard-grade MMF. This is the first time that a parallel link with this bandwidth at this per-channel rate has ever been demonstrated. For the transmitter, an SiGe laser driver was combined with a GaAs vertical-cavity surface-emitting laser (VCSEL) array. For the receiver, the signal from a GaAs photodiode array was amplified by a 12-channel SiGe receiver integrated circuit. Key to the demonstration were several custom testing tools, most notably a 12-channel pattern generator. The package is very similar to the commercial parallel modules that are available today, but the per-channel bit rate is three times higher than that for the commercial modules. The new modules demonstrate the possibility of extending the parallel-optical module technology that is available today into a distance-bandwidth product regime that is unattainable for copper cables.

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.

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.

1310nm VCSELs in 1-10Gb/s commercial applications

Beginning with 4 Gigabit/sec Fibre-Channel, 1310nm vertical-cavity surface-emitting lasers (VCSELs) are now entering the marketplace. Such VCSELs perform like distributed feedback lasers but have drive currents and heat dissipation like 850nm VCSELs, making them ideal for todays high-performance interconnects and the only choice for the next step in increased interconnection density. Transceiver performances at 4 and 10 Gigabits/sec over fiber lengths 10-40km are presented. The active material is extremely robust, resulting in excellent reliability.

120 Gb/s VCSEL-based parallel optical link and custom 120 Gb/s testing station

A 120 Gb/s optical link (12 channels at 10 Gb/s/ch) has been demonstrated. The link operated at a BER of less than 10/sup -12/ with all channels operating and with a total fiber length of 316 m, which comprises 300 m of next generation (OM-3) multimode fiber (MMF) plus 16 m of standard grade MMF. This is the first time that a parallel link with this bandwidth at this per-channel rate has ever been demonstrated. For the transmitter, a SiGe laser driver was combined with a GaAs VCSEL array. For the receiver, the signal from a GaAs photodiode array was amplified by a 12 channel SiGe receiver IC. Key to the demonstration is the use of several custom testing tools, most notably a 12-channel pattern generator. The package is very similar to the commercial parallel modules that are available today, but the per-channel bit rate is three times higher than for the commercial modules. The new modules demonstrate the possibility of extending the parallel optical module technology that is available today into a distance/spl times/ bandwidth regime that is unattainable for copper cables.

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.

High-power VCSEL arrays for consumer electronics

Finisar has developed a line of high power, high efficiency VCSEL arrays. They are fabricated at 860nm as traditional P side up top emitting devices, leveraging Finisar’s existing VCSEL fab and test processes for low cost, high volume capability. A thermal camera is used to accurately measure temperature profiles across the arrays at a variety of operating conditions and further allowing development of a full reliability model. The arrays are shown to demonstrate wear out reliability suitable for a wide range of applications. Typical 1/e^2 beam divergence is near 16 degrees under CW operating conditions at peak wall plug efficiency, narrowing further under pulsed drive conditions.