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Polymer multimode optical waveguides can enable high-speed short-reach optical interconnection at low cost within high performance electronic systems. The formation of such waveguides on flexible substrates can offer important additional advantages such as light weight, ability to be tightly bent, and reconfigurability which are particularly important in environments where space, weight, and shape conformity are critical, for instance in vehicles and aircraft. The ability of such flexible optical interconnects to be tightly bent and twisted with low excess loss is crucial in enabling their use in systems with limited space and with movable parts. As a result, in this work, we present a new design of such flexible polymer multimode waveguides that achieves improved bending loss performance over the conventional waveguide design. It is experimentally shown that the proposed design achieves a very low excess loss of 0.5 dB for a 3 mm radius bend under a 50 μm MMF launch. In comparison, flexible waveguides with the conventional design exhibit a 2 dB excess loss under the same launch and bend conditions. Additionally, useful rules that associate the twisting loss performance of flexible polymer waveguide samples with their geometric characteristics are derived. It is shown that negligible twisting losses (<0.1 dB for a 50 μm MMF input) can be achieved when the dimensions of the waveguide samples are appropriately selected. The results demonstrate the strong potential of such bend- and twist-insensitive flexible polymer waveguides for use in next-generation vehicles and aircraft. [ABSTRACT FROM AUTHOR]

Visible light communications have attracted considerable interest in recent years owing to the ability of low-cost light emitting diodes (LEDs) to act both as illumination sources and data transmitters with moderate data transmission rates. In this paper, we propose the formation of ultra-low cost visible-light integrated optical links by interfacing dense micro-pixelated LED arrays with matching multi-layered multimode polymer waveguide arrays. The combination of these two optical technologies can offer relatively high aggregate data densities ≥ 0.5 Tb/s/mm2 using very low cost components that can be directly interfaced with CMOS electronics and integrated onto standard printed circuit boards. Here, we present the basic system design and report the first proof-of-principle demonstration of such a visible light system employing 4×4 μLED arrays on a pitch matching four-layered waveguide array samples. Different interconnection topologies and light coupling schemes are investigated and their performance in terms of loss and crosstalk is compared. Data transmission of 2.5 Gb/s with a bit error rate within the forward-error correction threshold of 3.8×10−3 is achieved over a single μLED-waveguide channel using PAM-4 modulation and equalization. The results presented here demonstrate the potential of such ultra-low cost visible-light optical interconnects. [ABSTRACT FROM AUTHOR]

Polymer multimode waveguides on flexible substrates enable the formation of bendable low-cost optical interconnects that can be deployed in a wide range of applications. However, the highly multimoded nature of such guides in combination with the stress and mode mixing induced due to sample bending raise important concerns about the effect that sample flexure has on their bandwidth performance and potential to support high-speed data transmission. In this letter, we present data transmission studies on a 1-m long flexible spiral waveguide when flexure is applied. The flexible polymer sample is bent 180° around a cylindrical mandrel, and the loss and frequency response of the waveguide are obtained for radii of curvature down to 4 mm and are compared with the performance obtained when no flexure is applied. The bit-error-rate (BER) performance of the respective optical link is also recorded at data rates up to 40 Gb/s. A flat frequency response up to at least 30 GHz is demonstrated for all bending radii applied, and error-free (BER<10−12) data transmission is achieved for all data rates studied up to 40 Gb/s. The results clearly demonstrate that sample flexing does not result in any significant transmission impairments in such links and highlight the strong potential of this technology for use in high-speed board-level interconnections. [ABSTRACT FROM AUTHOR]

Power density and cooling issues are limiting the performance of high performance chip multiprocessors (CMPs), and off-chip communications currently consume more than 20% of power for memory, coherence, PCI, and Ethernet links. Photonic transceivers integrated with CMPs are being developed to overcome these issues, potentially allowing low hop count switched connections between chips or data center servers. However, latency in setting up optical connections is critically important in all computing applications, and having transceivers integrated on the processor chip also pushes other network functions and their associated power consumption onto the chip. In this paper, we propose a low latency optical switch architecture that minimizes the power consumed on the processor chip for two scenarios: multiple-socket shared memory coherence networks and optical top-of-rack switches for data centers. The switch architecture reduces power consumed on the CMP using a control plane with a simplified send and forget server interface and the use of a hybrid Mach-Zehnder interferometer and semiconductor optical amplifier integrated optical switch with electronic buffering. Results show that the proposed architecture offers a 42% reduction in head latency at low loads compared with a conventional scheduled optical switch as well as offering increased performance for streaming and incast traffic patterns. Power dissipated on the server chip is shown to be reduced by more than 60% compared with a scheduled optical switch architecture with ring resonator switching. [ABSTRACT FROM PUBLISHER]

Optical technologies have received large interest in recent years for use in board-level interconnects. Polymer multimode waveguides in particular, constitute a promising technology for high-capacity optical backplanes as they can be cost-effectively integrated onto conventional printed circuit boards (PCBs). This paper presents the first optical backplane demonstrator based on the use of PCB-integrated polymer multimode waveguides and a regenerative shared bus architecture. The backplane demonstrator is formed with commercially-available low-cost electronic and photonic components onto conventional FR4 substrates and comprises two opto-electronic (OE) bus modules interconnected via a prototype regenerator unit. The system enables interconnection between the connected cards over four optical channels, each operating at 10 Gb/s. Bus extension is achieved by cascading OE bus modules via 3R regenerator units, overcoming therefore the inherent limitation of optical bus topologies in the maximum number of cards that can be connected to the bus. Details of the design, fabrication, and assembly of the different parts of this optical bus backplane are presented and related optical and data transmission characterisation studies are reported. The optical layer of the OE bus modules comprises a four-channel three-card waveguide layout that is compatible with VCSEL/PD arrays and ribbon fibres. All on-board optical paths exhibit insertion losses below 13 dB and intra-channel crosstalk lower than -29 dB. The robustness of the signal distribution from the bus inputs to all respective bus output ports in the presence of input misalignment is demonstrated, while 1 dB input alignment tolerances of approximately ±10 μm are obtained. The electrical layer of the OE bus modules comprises the essential driving circuitry for 1×4 VCSEL and PD arrays and the corresponding control and power regulation circuits. The interface between the optical and electrical layers of the bus modules is achieved with simple OE connectors that enable end-fired optical coupling into and out of the on-board polymer waveguides. The backplane demonstrator achieves error-free (BER <; 10-12) 10 Gb/s data transmission over each optical channel, enabling therefore, an aggregate interconnection capacity of 40 Gb/s between any connected cards. [ABSTRACT FROM PUBLISHER]

Cost-effective multimode polymer waveguides, suitable for use in high-speed on-board optical interconnections, are presented. The fundamental light transmission properties of the fabricated waveguides are studied under different launch conditions and in the presence of input misalignments. Low loss (∼0.04 dB/cm at 850 nm) and low crosstalk (< -30 dB) performance, relaxed alignment tolerances (±20 μm) and high-speed operation at a 10-Gb/s data rate are achieved. No degradation in the high-speed link performance is observed when offset input launches are employed. Moreover, a range of useful waveguide components that add functionality and enable complex on-board topologies are presented. The optical transmission characteristics of the fabricated components are investigated and it is shown that excellent performance is achieved. Excess losses as low as 0.01 dB per waveguide crossing, the lowest reported value for such components, and bending losses below 1 dB for 90-degree and S-shaped bends are obtained even with multimode fiber launches. Moreover, high-uniformity power splitting and low-loss signal combining are achieved with Y-shaped splitter/combiners while a variable splitting ratio between 30%-75% is demonstrated with the use of multimode couplers. Overall, the devices presented are attractive potential candidates for use in on-board optical links. [ABSTRACT FROM AUTHOR]