Ultra-high-accuracy chromatic dispersion measurement in optical fibers

The chromatic dispersion in optical fibers is a key property for applications where a broadband light source is used and the timing of each individual wavelength is crucial. Counteracting the timing offset introduced by the fiber is a challenge in many applications especially in mode locked lasers. The dispersion parameters need to be measured with high precision. The length of the fiber, the temperature, and the used wavelength will highly impact the amount of dispersion and the accuracy of the measurement. We developed an ultra-high-accuracy dispersion measurement setup at 1080 ± 50 nm considering all the parameters that may influence the measurement. It is based on a home-built wavelength tunable laser where the output is modulated by an electro-optical modulator connected to a 24 GSamples/s arbitrary waveform generator to a complex pattern consisting of pulses and a 4 GHz sine wave. After passing through the fiber the signal is measured with an 80 GSamples/s real time oscilloscope. The fiber’s temperature is controlled to allow for reproducible measurements over several days and we achieve timing measurement accuracies down to ~200 fs. We also present the performance of the setup at ~850 nm. We will discuss and quantify all effects which can negatively impact the system accuracy and we will report on more cost-effective options using lower performance equipment.