Terry V. Clapp

Cost-Effective Multimode Polymer Waveguides for High-Speed On-Board Optical Interconnects

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 (plusmn20 mum) 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.

Fiber-device-fiber gain from a sol-gel erbium-doped waveguide amplifier

An erbium-doped silica-on-silicon planar waveguide optical amplifier is described. The active core is a topographic guide formed from aluminophosphosilicate glass doped with erbium and ytterbium. The buffer is formed from silica deposited by thermal oxidation and the cladding from borophosphosilicate glass obtained by plasma-enhanced chemical vapor deposition. The use of low process temperatures allows relatively heavy doping and careful control of the core etching allows low background insertion losses to be obtained. Spontaneous emission and gain measurements are given and 5.4-dB fiber-device-fiber gain is demonstrated using a 5-cm-long chip pumped using a 980-nm laser diode at 175-mW pump power.

Highly transparent silicone materials

Silicone based polymers possess a unique set of properties that makes them highly suitable for optical applications. In addition to their excellent thermal stability, mechanical properties, and ease of processing, they are highly transparent in the ultraviolet, visible, and selected bands of the near-IR spectra. The loss and absorption characteristics for a variety of silicone based polymers are examined and an example of a recently developed ultra-violet transparent polymer coating that is UV cured illustrates the flexibility of the silicone polymer family to be tailored to meet specific application needs.

Broadband variable optical attenuator in silica waveguide technology

A broad-band variable optical attenuator, with 1 dB flatness over the 1530-1560 range and with variable attenuation up to 20 dB, is described. It is based on cascaded Mach-Zehnders and fabricated in silica waveguide technology.

Terabit capacity passive polymer optical backplane

A novel, low-loss, low-crosstalk optical backplane with scalable architecture using a planar array of multimode polymer waveguides is presented. Passive strict non-blocking interconnection of 10-cards is enabled via 100 waveguides each capable of 10 Gb/s operation.

Low Loss and Low Crosstalk Multimode Polymer Waveguide Crossings for High-Speed Optical Interconnects

Multimode polymer waveguide crossings exhibiting the lowest reported excess loss of 0.006 dB/crossing and crosstalk values as low as -30 dB are presented. Their potential for use in high-speed dense optical interconnection architectures is demonstrated.

Liquid crystals in telecommunications systems

The first liquid crystal devices have recently been installed in the fibre optic networks that provide the backbone of the modern telecommunications system. Most optical network devices are concerned with the manipulation of the amplitude and phase of the optical signal. Liquid crystals have the highest figure of merit for field addressed electro-optic response and can have excellent transparency in the optical telecommunications window. Here we consider the importance of liquid crystals in controlling the phase and the state of polarisation of light in these systems. We also consider arrays of liquid crystal phase modulators, fabricated using LCOS technology, in holographic switches and multifunction devices.

Multimode siloxane polymer waveguides for robust high-speed interconnects

Novel multimode waveguide interconnects fabricated from high-reliability siloxane polymers are presented. The propagation characteristics are investigated and the viability of the waveguides for robust high-speed transmission at 10 Gb/s is successfully demonstrated.

Telluride Glass Fibres for Transmission in the 8-12 micrometres Waveband

Chalcogenide glass fibres have been developed for transmission in the 8-12 µm waveband. The bulk properties of a range of selenide and telluride glasses have been studied and compositions chosen to optimise transmission and glass stability. The role of major impurities and the procedures used to minimise them are described. Selected compositions have been drawn into long lengths of polymer coated fibre with diameters controlled accurately up to 500 µm. Current fibres transmit with losses of 5-10 dB m-1 in the 8-12 µm waveband. Approximately 4 dB m-1 of this loss is attributable to scattering. Mechanical testing has shown that fibre strength is determined by internal defects. Their elimination should enable fibres to sustain bend radii of the order of one centimetre, and at the same time should reduce minimum losses to below 1 dB m-1.

Modal noise investigation in multimode polymer waveguides

In this work the recent interest in waveguides for use in short optical links has motivated a study of the modal noise dependence on launch conditions in short-reach step-index multimode polymer waveguides. Short optical links, especially those with several connection interfaces and utilising a restricted launch are likely to be subject to a modal noise power penalty. We therefore experimentally study the modal noise impact of restricted launches for a short-reach optical link employing a 50 x 50 μm polymer multimode waveguide. Lens launches resulting in small diameter input spots are investigated as are restricted launches from an 8 μm core optical fibre. For a launch spot of 10 μm diameter no impairment is observed for up to 9 dBo of mode selective loss, and for a fibre launch with a dynamic input movement of 6 μm no impairment is seen for up to 8 dBo of mode selective loss.