Characterization of differential modal group delay in few-mode fiber using a digital re-sampling technique

We characterize the differential modal group delay (DMGD) arising in few-mode fibers (FMFs) based on the digital re-sampling technique, which is commonly used in current digital signal processing flow at the receiver-side. When the DMGD of a 291-m two-mode fiber is characterized over the C-band by using a 500-Mb/s non-return-to-zero (NRZ) signal and 1-GSa/s real-time oscilloscope, the experimental results are consistent with the DMGD obtained from the traditional time-of-flight (TOF) method. However, the wide-bandwidth instruments of the traditional TOF method can be replaced by cheap ones with a bandwidth of only a few hundred MHz, but the same temporal precision is achieved. Moreover, our proposed DMGD characterization method is not limited by the number of guided modes arising in the FMF, together with the capability to obtain both the DMGD value and its sign between two arbitrary guided modes.