High-speed Optical Data Links Research Articles

Superconducting Processor Modulated VCSELs for 4K High-Speed Optical Data Link

Superconducting processor based on single flux quantum (SFQ) technology is a promising solution for cryogenic computing with high-speed operation at extremely low power. However, energy-efficient data link from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim 4\text{K}$ </tex-math></inline-formula> operation to room temperature (RT) users has been remained as a key challenger to be resolved. In this work, we report the 5K performance of 51.56 Gb/s PAM-4 optical data link from a VCSEL, coupled by free-space optics inside cryostat to RT receiver through cryostat optical window. Finally, a superconducting bit pattern generator (BPG) is used to modulate a VCSEL at 4 K: 12.5 Gb/s NRZ error-free optical data transmission and 20 Gb/s NRZ open eye-diagrams are demonstrated via an OM4 fiber coupled directly to the VCSEL at 4 K inside cryostat and linked to the outside receiver at RT.

Polarization independent and temperature tolerant AWG based on a silicon nitride platform.

A polarization tolerant optical receiver is a key building block for the development of wavelength division multiplexing based high-speed optical data links. However, the design of a polarization independent demultiplexer is not trivial. In this Letter, we report on the realization of a polarization tolerant arrayed waveguide grating (AWG) on a 300-mm silicon nitride (SiN) photonic platform. By introducing a series of individual polarization rotators in the middle of the waveguide array, the polarization dependence of the AWG has been substantially reduced. Insertion losses below 2.2 dB and a crosstalk level better than -29dB has been obtained for transverse electric and transverse magnetic polarizations on a four-channel coarse AWG. The AWG temperature sensitivity has also been evaluated. Thanks to the low thermo-optical coefficient of SiN, a thermal shift below 12 pm/°C has been demonstrated.

Design of a multigigabit optical network interface card

High-speed optical data links enable local area networks (LANs) that operate at data rates above 10 Gb/s. Various network, protocol and switch architectures have been proposed that use these links. The optical network interface card (ONIC) is an important component for demonstrating efficient application of these architectures. In this paper, we describe the design of a programmable ONIC that interfaces a 12-channel gigabit parallel optical link module with a 64-bit/66-MHz PCI computer bus. Hardware programmability (using FPGAs) enables the ONIC to efficiently implement different communication protocols. For hardware testing, the ONIC hardware was programmed for bit error rate (BER) analysis. In continuous operation at 8 Gb/s for 30 days through a 1-m fiber, no errors occured. For application testing, a custom ONIC software driver was developed. We used this driver to demonstrate message passing between applications running on two ONIC-equipped servers. The ONIC design provides a low-cost solution that can be readily adapted for application and device specific requirements. The use of ONIC in a free-space optical switch system is described here.

Development of a visible VCSEL-to-plastic optical fibre module for use in high-speed optical data links

This paper presents a portion of the results that have emerged to date from the ESPRIT Long Term Research Project Bright Red Surface Emitting Lasers (BREDSELS-23455). The project's main objective has been to develop arrays of Vertical Cavity Surface Emitting Lasers (VCSELs) emitting in the region of 650 nm. These VCSEL arrays, suitably coupled to plastic fibre ribbon, are potentially ideal sources for high-speed plastic optical fibre networks. Linear 1×8 VCSEL arrays have been fabricated with individual elements generating a peak room temperature power of 2 mW at 666.8 nm. These devices are capable of operating continuous wave to a temperature of 50°C. The use of selective oxidation in the fabrication process is found to be essential. A brief description of the device results and POF module are presented.

HIGH-PERFORMANCE, PRODUCIBLE VERTICAL-CAVITY LASERS FOR OPTICAL INTERCONNECTS

In this paper we review the state-of-the-art performance of producible, 850 nm, current-guided GaAs/AlGaAs , top-emitting vertical cavity surface emitting lasers (VCSELs). We discuss the motivation and desired characteristics for pursuing VCSELs, particularly in the area of high speed optical data links. We demonstrate that this structure is indeed producible and reproducible using MOVPE, where exceptional uniformity across wafers and arrays is obtained from commercial chambers. Record performance is also reported using MOVPE-grown GaAs VCSELs. These records include submilliamp (0.68 mA) CW room temperature threshold currents, &lt;1.6 V threshold voltages, over 28% total wall-plug efficiency, over 59 mW of (unbonded) power, 200° C lasing, operation over a 100 nm wavelength regime, and other records that rival or exceed those obtained even from strained-layer InGaAs VCSELs of any structure. We also present novel extensions of this base VCSEL platform for lateral mode control, illustrating the flexibility and extendibility of this technology. Finally application of these arrays as 32-channel-wide Opto-Electronic Technology Consortium (OETC) parallel links are shown with error free operations up to 700 Mbits/s (Manchester coded) through 100 m of fiber.