We present experience with photonic crystal fiber (PCF) characterization during COST Action 299, focusing on
phenomena causing errors and ways to mitigate them. PCFs developed at IPHT Jena (Germany) and UMCS Lublin
(Poland), designed for single mode operation were coupled to test instruments by fusion splicing to intermediate lengths
of telecom single mode fibers (SMF).
PCF samples were short (0.5-100 m), with 20-70 dB/km attenuation at 1310 nm and 1550 nm. Optical Time Domain
Reflectometer (OTDR) was best for measuring loss as most PCFs produced strong backscattering, while variable splice
losses and difficulties with PCF cleaving for optical power measurements made cutback and insertion loss measurements
inaccurate. Experience with PCF handling and cleaving is also reviewed.
Quality of splices to fiber under test was critical. Excitation of higher order modes produced strong "noise" during
measurements of polarization parameters like PMD or PDL. Multimode propagation and vibration-induced interference
precluded testing of fine dependence of PMD on temperature or strain, causing random variations comparable to true
changes of PMD. OTDR measurements were not affected, but testing of short fiber sections with very different
backscattering intensities puts special demands on instrument performance.
Temperature testing of liquid-infiltrated PCF was time-consuming, as settling of parameters after temperature change
took up to 40 minutes. PCFs were fragile, breaking below 2% linear expansion, sometimes in unusual way when twisted.