Interference phenomenon on the complex degree of coherence

A two-beam interferometer (TBI) with a two-mode fiber (TMF) as a dispersive medium in one arm and air in the other provides evidence of interference related to the complex degree of coherence similar to. A TMF with a low differential group delay (DGD) is used to measure the interference effect, since the overlapping of each individual mode at the output of a TMF is easily and artificially created in the vicinity of the zero DGD wavelength. When similar to 01 and similar to 11, respectively, are the complex degrees of coherence for the interferences between the LP 01 and LP 11 modes propagating through a TMF and a wave traversing air-path, the interference effect can be verified using the relationship similar to similar to similar to 2 = similar to similar to 01 + similar to 11 similar to 2. The experiments are carried out using a low coherence source and three kinds of TMFs with zero DGD wavelengths around 1550 nm. It is clearly observed that similar to similar to similar to 2-response waveforms have oscillatory structures due to the interference between similar to 01 and similar to 11. A similar to similar to similar to 2-response measurement employing the TBI reveals that the theoretically obtained similar to similar to similar to 2-curves well reflect similar to similar to similar to 2-curve obtained experimentally for a temporally overlapped wave composed of the two modes. To the best of our knowledge, this is the first experimental demonstration of the interference between complex degrees of coherence.