1 January 1988 Amplitude And Phase Characterisation Of Polished Directional Half-Couplers With Variable Refractive Index Overlays
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Optical Engineering, 27(1), 270145 (1988). doi:10.1117/12.7976640
Abstract
We report a characterisation technique for both amplitude and phase variations of polished fibre half-couplers in the proximity of variable index bulk overlays. Experimental results are compared with simple theoretical models. In addition, simple derivative fibre-based devices are reported. Amplitude measurements were performed using a single fibre embedded in a block with a 25 cm radius groove, polished to within 1um of the core. A linear (in decibels) change in attenuation resulted for overlay indices greater than the effective mode index. An attenuation change of 40 dB was observed for a 0.0026 change in index. To observe phase changes, an interferometric approach was taken. Two fibres were embedded, one above the other, in a block identical to that above. The core of the top fibre only was exposed by polishing. Low loss 50:50 fused taper couplers were spliced to both sides of the block, forming a fibre Mach-Zehnder interferometer. For overlay indices less than the effective mode index, a phase change of rad was observed for an index change of 0.0045, with an interaction length of 700um.
M. C. Brierley, C. A. Millar, "Amplitude And Phase Characterisation Of Polished Directional Half-Couplers With Variable Refractive Index Overlays," Optical Engineering 27(1), 270145 (1 January 1988). http://dx.doi.org/10.1117/12.7976640
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KEYWORDS
Polishing

Refractive index

Signal attenuation

Interferometry

Mach-Zehnder interferometers

Phase interferometry

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