Characterization of photonic crystal fibres with OTDR

Optical time domain reflectometer (OTDR) is versatile tool for characterization of optical fibres in telecom networks. Measurements of several silica-based photonic crystal fibres (PCFs) during COST Action 299 proved OTDR is useful for measuring PCFs as well. OTDR was able to provide relatively accurate fiber attenuation data even when high splice/coupling loss and propagation of higher order modes in holey structure made other methods unreliable. Several PCFs tested had highly doped core, produced intense backscattering - up to 200× stronger in comparison to single mode telecom fibres (SMF) and had high attenuation (20-200 dB/km), which allowed to measure fibre loss in short samples (16 - 100 m) and improved dynamic range of measurement. It was also possible to locate optical defects in PCFs and measure fusion splice loss in hybrid SMF-PCF circuits. Use of typical OTDR in PCF testing is unfortunately limited to characterization of rather short samples at few fixed wavelengths only.