Raman-induced photon correlations in optical fiber solitons

Recent experimental results on edge-filtered (also referred to as low- and high-pass filters) subpicosecond optical solitons have raised a number of theoretical questions concerning the origin of the reduced photon- number fluctuations. One of the main experimental results was that for long fibers, on the order of 100 soliton periods, the measured photon-number squeezing increased with propagation distance in contrast with theoretical calculations for picosecond solitons at that time. Here I present theoretical results on photon statistics of edge-filtered subpicosecond optical solitons. The numerical simulations include coupling to phonons via a Raman interaction, in addition to the electronic Kerr nonlinearity, and are in good agreement with the experimental data over the range of propagation distances investigated so far. The theoretical results clearly show that the phenomena observed are not related to long fiber propagation but to the Raman self-frequency shift and should be more clearly observable using cooled fiber.