A probe that enables optical coupling to planar lightwave circuits (PLCs) is described. A flexible waveguide is used to form a variable length directional coupler that extracts light from a waveguide in the wafer to the probe. Varying the length enables optimal coupling to be achieved for a wide range of probe-to-waveguide gap, materials, widths and cladding thicknesses present on a chip. In this paper we consider the use of SU-8 polymer as waveguide test probe and polydimethylsiloxane (PDMS) as cladding for the probe. The results indicate that this approach is ideal for characterizing PLC's as the 3dB bandwidth of the probe covers the whole 1300 -1700 nm fiber-optic telecommunication range. Coupling length control in the range of 50-200 mm leads to maximum coupling in excess of 80% for the range of conditions investigated. © 2007 IEEE.