Laser and Photodetector Testing for Ultrahigh-Speed Optical Links
Abstract
The exponential increase of the communication system bandwidth is propelled by data-driven applications in high performance computing (HPC) and data centers. Massive data centers housing exabytes of information are becoming the backbones of many emerging industries, and it is predicted the data center bandwidth will see a CAGR of over 30% for the foreseeable future. Optical interconnects based on 850 nm oxide-confined Vertical-Cavity Surface-Emitting Lasers (oxide-VCSELs) and multi-mode fibers (MMFs) have become the industry standard in datacom applications, and the technology has developed towards higher speed, such as 100 Gb/s (4 x 25Gb/s) active optical cables (AOCs). On the receiver side, the development of high-speed photodetectors is equally important. In 2014, Professor Milton Feng at the University of Illinois led the 850 nm oxide-VCSELs research in USA and demonstrated 40 Gb/s error-free (BER < 10-12) data transmission and ultralow laser relative intensity noise (RIN) reaching the Òstandard quantum limitÓ. Since 2015, FengÕs High-Speed IC research group became the world leader in VCSELs by demonstrating a record performance of 57 Gb/s error-free transmission at 25 ?C and a new record of 50 Gb/s error-free transmission at 85 ?C. Currently, we have expanded our research area to low-noise and high-speed 850 nm photodetectors and thus complete the transmitter-receiver full optical link solution. With a rich history established by Professor Nick Holonyak and Professor Gregory Stillman in the area of compound semiconductor lasers, P-i-N photodetectors, and THz heterojunction bipolar transistors, we believe we are the top contender in developing next-generation high-speed P-i-N photodetectors for 50 to 100 Gb/s optical receivers. In an optical communication system, the noise sources include the thermal noise, the shot noise of photodetectors, and most importantly, the relative intensity noise (RIN) of lasers. The RIN is a significant source of signal fidelity degradation especially in multi-level modulation schemes such as pulse-amplitude modulation (PAM) where the signal-to-noise ratio (SNR) error margin is limited. Our High-Speed IC research group has demonstrated Òquantum-limited RINÓ for our 40 Gb/s oxide-VCSEL , and a record ultra-low RIN for Transistor Lasers (TLs), which correlates to the fast electron-hole spontaneous recombination lifetime at the ground and the 1st excited states. To characterize the noise characteristics of > 50 Gb/s data transmission rate optical links, a high-bandwidth and ultra-low noise floor electrical spectrum analyzer is needed. For P-i-N photodetector bandwidth characterization, the industry standard is to analyze the photodetector impulse response to femtosecond laser pulse and perform Fourier transform to obtain the detector bandwidth. Thus to further enhance our noise characterization capability, we are proposing to purchase a Keysight N9030B spectrum analyzer with options for noise floor reduction and noise figure measurement for high-performance noise and signal mixing characterization. For the high-speed photodetector bandwidth characterization, we propose to purchase a Calmar Laser Mendocino FRL-02RFF1 fiber laser along with a variety of components, listed in the budget table, to establish the femtosecond laser pulse measurement setup. The proposed equipment will further expand our high-speed and ultra-low noise characterization capability to include the complete optical link, both transmitters and receivers. With careful operation and maintenance the estimated useful life of the equipment will be > 10 years.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- May 28, 2019
- Source ID
- W911NF1910127
Entities
People
- Milton Feng
Organizations
- Army Contracting Command
- United States Army
- University of Illinois Urbana–Champaign