Andrew S. Webb

Suspended-core holey fiber for evanescent-field sensing

A simple fabrication technique for a silica suspended-core holey fiber design is presented that features a higher air-filling fraction than most holey fibers, making it ideal for evanescent-field-sensing applications. The holes in the fiber are defined through mechanical drilling of the preform, which is a significantly quicker and more straightforward approach to the customary stacking method. During the draw, the shape of the holes are manipulated so that the final fiber design approximates that of an air-suspended rod with three fine struts supporting the core. Modeling reveals that the modal overlap is greater than 29% at 1550 nm for a core diameter of 0.8 µm, which is significantly higher than any previously reported index-guiding structure used for sensing. A basic gas sensor is demonstrated using acetylene as the sensing medium and the results are reported.

Fiber design for high-power fiber lasers

This paper reviews the progress in active fibers suitable for power scaling, highlighting the advances in fiber design that will enable the control of nonlinearities such as SRS and SBS in high power fiber lasers, as well as making feasible a practical high power three-level system.

Erbium-doped multi-element fiber amplifiers for space-division multiplexing operations

Erbium-doped multi-element fiber (MEF) amplifiers have been fabricated to simultaneously amplify multiple transmission channels. MEF devices comprise of multiple single-core fibers (elements) combined in a common coating, with each element working as a single fiber in isolation. MEFs containing 3-elements and 7-elements have been fabricated and characterized. Each element of the fabricated MEFs provides nearly 32 dB of gain with a noise figure of <5 dB for an input signal level of -23 dBm at 1530 nm. Different permutations of element pairs within the MEFs were checked for crosstalk and none was detected, confirming the simultaneous multi-channel amplification capabilities of MEFs.

Direct UV Written Optical Waveguides in Flexible Glass Flat Fiber Chips

A glass-based substrate technology that fills the gap between a truly flexible extended length distributed sensor medium and the multifunctionality of optical chips is demonstrated. Flat fiber chips will open further degrees of freedom to control the behavior of light via mechanical manipulation. A flexible flat format will also allow straightforward incorporation into smart structures. Coupled with low manufacturing costs, these flexichips can also be a key enabler to disposable high-end sensing devices or fully distributed point sensors. In this study, Bragg gratings were used to demonstrate the optical flatness of the flat fiber core layer. Furthermore, the effective index values obtained from the grating experiment were input into a dynamic model, subsequently proving the influence of the dumbbell-shaped flat fiber cross section on the resultant UV written waveguides. Evanescent field sensing was also demonstrated by adopting a stepped Bragg approach.

488 nm irradiation induced photodarkening study of Yb-doped aluminosilicate and phosphosilicate fibers

Photodarkening in highly Yb-doped aluminosilicate and phosphosilicate fibers, under 488 nm irradiation, is presented. Both irradiation-induced excess loss and post-irradiation temporal loss evaluations reveal that Yb-doped phosphosilicate fiber is highly resistant to photodarkening.

Novel fabrication method of highly-nonlinear silica holey fibres

We present a novel and simple method of producing small core silica holey fibres with nonlinearity close to the maximum achievable. An effective area of 1.6 mum2 with a loss of 0.18 dB/m at 1.55 mum were achieved.

Fabrication of a Multimode Interference Device in a Low-Loss Flat-Fiber Platform Using Physical Micromachining Technique

A physical micromachining technique is demonstrated in a low-loss flat-fiber substrate to fabricate a multimode interference (MMI) device. The flat-fiber substrate is a low-index-contrast material; however, by making use of two physically micromachined trenches, lateral confinement is achieved providing high index contrast for the MMI region. A 1 × 3 MMI device exhibiting 1.89 dB of excess loss has been demonstrated.

Evanescent field sensing in novel flat fiber

Recently developed novel psilaflat fiberpsila substrate promises flexible, long-haul integrated optical devices. Here, we present the first demonstration of one such device; an evanescent field sensor, based upon direct UV written Bragg gratings.

Precision laser processing for micro electronics and fiber optic manufacturing

The application of laser based materials processing for precision micro scale manufacturing in the electronics and fiber optic industry is becoming increasingly widespread and accepted. This presentation will review latest laser technologies available and discuss the issues to be considered in choosing the most appropriate laser and processing parameters. High repetition rate, short duration pulsed lasers have improved rapidly in recent years in terms of both performance and reliability enabling flexible, cost effective processing of many material types including metal, silicon, plastic, ceramic and glass. Demonstrating the relevance of laser micromachining, application examples where laser processing is in use for production will be presented, including miniaturization of surface mount capacitors by applying a laser technique for demetalization of tracks in the capacitor manufacturing process and high quality laser machining of fiber optics including stripping, cleaving and lensing, resulting in optical quality finishes without the need for traditional polishing. Applications include telecoms, biomedical and sensing. OpTek Systems was formed in 2000 and provide fully integrated systems and sub contract services for laser processes. They are headquartered in the UK and are establishing a presence in North America through a laser processing facility in South Carolina and sales office in the North East.

Multi-element fiber for space-division multiplexing

A novel approach of using multi-element fiber (MEF) technology in space-division multiplexing (SDM) systems is presented. This paper reviews the progress in fabrication and characterization of MEF based both ultralow crosstalk transmission and amplifier fibers. Passive 3-element MEFs have been successfully demonstrated for application in telecommunications. An active 5-element MEF amplifier has also been demonstrated in a novel multiport cladding-pumped configuration, in which a central un-doped multi-mode pump fiber-element is surrounded by four Er/Yb-doped active fiber-elements. MEF is compatible with current WDM systems, and there is no need to develop specialized multiplexing/demultiplexing components. Moreover, it offers a smooth upgrade to SDM systems.