Douglas Llewellyn Butler

Multicore fiber for optical interconnect applications

We propose multicore fibers with linear array configurations for optical interconnect applications. We discuss fiber design considerations and present actual 1×4 and 2×4 fiber results.

Multicore optical fiber and connectors for high bandwidth density, short reach optical links

Multicore fiber technology can play a key role in very high bandwidth density optical interconnects that will be needed for short range communications in next-generation data centers and high performance computers.

Measurements of cross-phase modulation induced crosstalk in an L-band EDFA

We measure the cross talk due to cross phase modulation in an L-band erbium-doped fiber amplifier (EDFA). The effect is larger than the one seen in C-band amplifiers and becomes the dominant effect in some wavelength-division multiplexing systems.

High-speed, bi-directional dual-core fiber transmission system for high-density, short-reach optical interconnects

A complete single mode dual-core fiber system for short-reach optical interconnects is fabricated and tested for high-speed data transmission. It includes dual-core fibers capable of bi-directional data transmission, dual-core simplex LC connectors, and fan-outs. The transmission system offers simplified bi-directional traffic engineering with integrated bidirectional transceivers and compact system design, utilizing simplex dual-core LC connectors that use half the space while increasing the bandwidth density by a factor of two. The fiber has two cores that are compatible with single mode fiber and conforms to the industry standard outer diameter of 125 μm. This reduces operational complexity by reducing the size and number of fibers, cables and connectors. Measured OTDR loss for both cores was 0.34 dB/km at 1310 nm and 0.19 dB/km at 1550 nm. Crosstalk for a piece of 5.8 km long dual-core fiber was measured to be below -75 dB at 1310 nm, and below -40 dB at 1550 nm. Both free-space optics fan-outs and tapered-fiber-coupler based MCF fan-outs were evaluated for the transmission system. Error-free and penalty-free 25 Gb/s bi-directional transmission performance was demonstrated for three different fiber lengths, 200 m, 2 km and 10 km, using the complete all-fiber-based system including connectors and fan-outs. This single mode, dual-core fiber transmission system adds complementary value to systems where additional increases in bandwidth density can come from wavelength division multiplexing and multiple bits per symbol.

Space Division Multiplexing in Short Reach Optical Interconnects

Many technical capabilities of space division multiplexed systems like low loss and crosstalk have been established in numerous long-haul system experiments. Recently more attention has been given to applications of space division multiplexing for short reach systems, including data center transmission and sensing applications. Short reach systems may be the first high volume application, as space division multiplexing for short reach systems has fewer remaining technical challenges. In addition to higher bandwidth density, space division multiplexed systems offer potential advantages in lower power consumption and cost. In this paper we present penalty-free bit error ratio results down to

Wavelength tunable high-power single-mode 1060-nm DBR lasers

10^{-12}

Pluggable multimode edge connector for glass-based electro-optical circuit boards (EOCB)

from system tests on 200 meters of 8-core multicore fiber with fan-outs and up to 2 km in dual-core multicore fiber with connectors and fan-outs.

Low-profile fiber connector for co-packaged optics

The wavelength tunable 1060-nm distributed Bragg reflector (DBR) laser chip consists of three sections: a gain section for lasing, and phase and DBR sections for wavelength control. A micro-heater is lithographically integrated on the top of the DBR section to tune the emission wavelength. The phase section is designed with either a top heater or by current injection to provide fine tuning of the wavelength. The wavelength tuning efficiency of our DBR laser is approximately 9 nm/W at the laser heat sink temperature of 25°C. Single-mode output powers of 686 mW and 605 mW were obtained at a CW gain drive current of 1.25 A and heat sink temperatures of 25°C and 60°C, respectively. Gain-switching by applying 1.1 GHz sinusoidal signal mixed with 600 mA DC injection current produced approximately 58 ps long optical pulses with 3.1 W peak power and 228 mW average power. The average power increased to 267 mW and pulse width broadened to 70 ps with DC bias of 700 mA. In CW operation, one of the applications for high-power single-mode DBR lasers is for non-linear frequency conversion. The light emitted from the 1060-nm DBR laser chip was coupled into a single-mode periodically poled lithium niobate (PPLN) crystal waveguide. Up to 350 mW optical power at 530 nm with the wall-plug efficiency of up to 15% was demonstrated.

Bend-insensitive optical fiber with high-mechanical reliability for silicon photonic packaging

Glass waveguides fabricated by ion-exchange are a promising technology for short reach on-board optical interconnects. We developed an optical connector concept for the interconnection of multimode glass waveguides to fiber ribbon cables. Our concept is based on the MXC expanded beam connector, and it uses a modified version of the US Conec PRIZM MT ferrule that is installed on the edge of the glass waveguide panel by adhesive bonding. The paper will discuss the connector concept, the assembly process, the demonstrator platform and the characterization results.

350 mW green light emission from a directly frequency-doubled DBR laser in a compact package

We developed a small form factor connector that can be assembled on all four sides of a high-data switch package for fiber connectivity. This paper discusses a novel connector approach that has the potential to meet all co-packaging requirements including solder-reflow-compatibility, de-mateability, low insertion loss and state-of-the art FAU attach. The connector was attached to the PIC for performance evaluation. The average insertion loss across all eight fibers of the assembly was 1.77 dB, including the three optical interfaces: (1) MT-to-MT between connector and receptacle, (2) receptacle-to-PLC and (3) PIC-to-FAU. Also included is the propagation loss of the PIC waveguide. Optical return loss was measured to be -55 dB or lower.