Jonathan E. Proesel

A 71-Gb/s NRZ Modulated 850-nm VCSEL-Based Optical Link

We report error free (BER <; 10-12) operation of a directly non-return-to-zero modulated 850-nm vertical cavity surface-emitting laser (VCSEL) link operating to 71 Gb/s. This is the highest error free modulation rate for a directly modulated laser of any type. The optical link consists of a 130-nm BiCMOS driver IC with two-tap feed-forward equalization, a wide bandwidth 850-nm VCSEL, a surface illuminated GaAs PIN photodiode, and a 130-nm BiCMOS receiver IC.

A 90nm CMOS integrated Nano-Photonics technology for 25Gbps WDM optical communications applications

The first sub-100nm technology that allows the monolithic integration of optical modulators and germanium photodetectors as features into a current 90nm base high-performance logic technology node is demonstrated. The resulting 90nm CMOS-integrated Nano-Photonics technology node is optimized for analog functionality to yield power-efficient single-die multichannel wavelength-mulitplexed 25Gbps transceivers.

35-Gb/s VCSEL-Based optical link using 32-nm SOI CMOS circuits

A VCSEL-based multimode fiber optical link using 32nm SOI CMOS circuits is demonstrated. Record optical link power efficiencies of 1pJ/bit at 25Gb/s and 2.7pJ/bit at 35Gb/s are achieved.

A 50 Gb/s NRZ Modulated 850 nm VCSEL Transmitter Operating Error Free to 90 °C

We report on the properties of an 850 nm vertical cavity surface-emitting laser (VCSEL) transmitter running at 50 Gb/s with NRZ modulation from 30 °C to 90 °C. This is the highest transmitter operating temperature at 50 Gb/s for a VCSEL link of any wavelength. This achievement is made possible by a combination of a high speed VCSEL design and driver and receiver circuits that incorporate equalization. Without equalization, the highest temperature attained with bit error ratio <;1E-12 is 57 °C.

25Gb/s 3.6pJ/b and 15Gb/s 1.37pJ/b VCSEL-based optical links in 90nm CMOS

Future high-performance computing systems require sub-2pJ/bit power efficiencies at >;10Gb/s [1-2]. The best reported optical link efficiencies at these data rates are ≥2.5pJ/bit [1-4]. This paper describes two VCSEL-based multimode (MM) fiber optical links achieving sub-2pJ/bit power efficiency from 15Gb/s to 22Gb/s. The links realized in 90nm CMOS share the same TX but use two different RXs that explore different aspects of the power/BW/area tradeoff.

Mismatch analysis and statistical design at 65 nm and below

Transistor sizing to control random mismatch is investigated. Input offset voltage of 65 nm bulk CMOS SRAM sense amplifiers are measured to analyze NMOS and PMOS threshold voltage (Vtn, Vtp) variation effects and compare them with statistical models and Pelgrom model predictions. A linear statistical response surface model (RSM) relating input offset to Vtn and Vtp is shown to agree well with measured results. Designs optimized using the RSMs produce circuits with 25% lower input offset voltage spread at a cost of 10% more active device area. Statistical models for post-manufacturing configuration are postulated and shown for sub-65 nm technologies.

Demonstration of a High Extinction Ratio Monolithic CMOS Integrated Nanophotonic Transmitter and 16 Gb/s Optical Link

We present a 16-Gb/s transmitter composed of a stacked voltage-mode CMOS driver and periodic-loaded reverse biased pn junction Mach-Zehnder modulator. The transmitter shows 9-dB extinction ratio and 10.3-pJ/bit power consumption and operates with 1.3 μm light. Penalties as low as 0.5 dB were seen as compared to a 25-Gb/s LiNbO3 transmitter with both a monolithic metal-semiconductor-metal receiver and a reference receiver at 16-Gb/s operation. We also present an analytic expression for relative transmitter penalty (RTP), which allows one to quickly assess the system impact of design parameters such as peak-to-peak modulator drive voltage, modulator figure of merit, and transmitter extinction ratio to determine the circumstances under which a stacked CMOS cascode driver is desirable.

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.

A monolithic 56 Gb/s CMOS integrated nanophotonic PAM-4 transmitter

We report a demonstration of four-level pulse amplitude modulation (PAM-4) using a segmented traveling-wave silicon photonic Mach-Zehnder modulator with monolithically integrated CMOS drivers. The PAM-4 transmitter shows clear eye openings up to 28 Gbaud.

Optical receivers using DFE-IIR equalization

Future computing systems will require increasingly high bandwidth to supply data to microprocessors, FPGAs, and other computational blocks [1,2]. Increasing data rate is a common solution, as I/O pad density is not scaling with bandwidth requirements. Copper interconnect has increasingly high loss with frequency, requiring complex, power-hungry equalization to overcome the channel response at high data rates. In contrast, optical interconnect can transport signals over long distances without complex equalization. Chip-to-chip optical interconnect will require sensitive, low-power, clocked receiver (RX) circuits that operate at high data rates. Conventional TIA-based RXs [1,2] require high power to maximize gain and minimize noise while maintaining high BW. A low-noise, low-BW, low-power TIA is combined with a 2-tap DFE to achieve high sensitivity in [3], but the data rate is 4Gb/s and limited dynamic range is demonstrated. Double-sampling architectures eliminate the TIA, replacing it with a large resistor [4] or a capacitive integrator [5], which decreases the front-end BW. The BW is equalized by double sampling, which is equivalent to a 2-tap FFE. However, the use of small sampling capacitors in [4,5] adds kT/C noise, limiting sensitivity. In this work, we demonstrate an optical RX with a large input resistance to maximize gain and sensitivity, while DFE with IIR feedback (DFE-IIR) [6] eliminates the resulting ISI with minimal added noise.