Pulse distortion and the square of the degree of coherence in the presence of second- and third-order dispersions

Abstract

A white-light source used in combination with a two-beam interferometer provides the same information about the dispersive nature of optical fibers as a femtosecond pulse from a laser source. The shape of the coherence curve in relation to the square of the degree of coherence, | γ |2, reflects the dispersion-induced pulse shape. We induce a third-order dispersion (TOD) effect on the | γ |2 in a two-beam interferometer composed of nondispersive and dispersive arms. A theoretical treatment predicts an oscillatory structure near the trailing edge of the | γ |2–curve due to TOD. Experiments are performed using low coherence sources, a few-mode fiber and a dispersion-shifted fiber near the zero chromatic-dispersion wavelengths of 1300 and 1550 nm, respectively. As a result, the experimentally obtained | γ |2-response well reflects that obtained theoretically for an unchirped wave with a Gaussian spectrum. Therefore, the | γ |2-response interferometric technique has the potential to simulate an ultra-short pulse transmission in the group velocity approximation.