The Molonglo Observatory Synthesis Telescope, operating at 843 MHz with a 5 square degree field of view, is carrying out a radio imaging survey of the sky south of declination −30 • . This survey (the Sydney University Molonglo Sky Survey, or SUMSS) produces images with a resolution of 43 ′′ × 43 ′′ cosec |δ| and an rms noise level of ∼ 1 mJy beam −1 . SUMSS is therefore similar in sensitivity and resolution to the northern NRAO VLA Sky Survey (NVSS; Condon et al. 1998). The survey is progressing at a rate of about 1000 square degrees per year, yielding individual and statistical data for many thousands of weak radio sources. This paper describes the main characteristics of the survey, and presents sample images from the first year of observation.

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1È2 mJy beam~1 (1 p), and the positional accuracy is B1@@ ] 1@@ csc o d o for sources brighter than 20 mJy. The dynamic range is no better than 250 : 1, and this also constrains the sensitivity in some parts of the images. The survey area of 330 deg2 contains well over 1.2 ] 104 unresolved or barely resolved objects, almost all of which are extragalactic sources lying in the zone of avoidance. In addition, a signiÐcant fraction of this area is covered by extended, di †use emission associated with thermal complexes, discrete H II regions, supernova remnants, and other structures in the Galactic interstellar medium.

The development of microstructured fibres offers the prospect of improved fibre sensing for low refractive index materials such as liquids and gases. A number of approaches are possible. Here we present a new approach to evanescent field sensing, in which both core and cladding are microstructured. The fibre was fabricated and tested, and simulations and experimental results are shown in the visible region to demonstrate the utility of this approach for sensing.