Propagation of temporal mode multiplexed optical fields in fibers: influence of dispersion

TL;DR

This study examines how fiber-induced dispersion affects the spectral and interference properties of temporally multiplexed optical fields, revealing mode orthogonality effects and methods for dispersion compensation to preserve quantum information.

Contribution

It provides experimental insights into the impact of dispersion on temporal mode interference and proposes techniques for spectral distortion recovery in fiber networks.

Findings

Interference visibility depends on unbalanced dispersion and mode order.

Modes with order $k extgreater=2$ can become orthogonal due to dispersion.

Dispersion compensation can restore spectral and temporal mode integrity.

Abstract

Exploiting two interfering fields which are initially in the same temporal mode but with the spectra altered by propagating through different fibers, we characterize how the spectra of temporal modes changes with the fiber induced dispersion by measuring the fourth-order interference when the order number and bandwidth of temporal modes are varied. The experiment is done by launching a pulsed field in different temporal modes into an unbalanced Mach-Zehnder interferometer, in which the fiber lengths in two arms are different. The results show that the mode mismatch of two interfering fields, reflected by the visibility and pattern of interference, is not only dependent upon the amount of unbalanced dispersion but also related to the order number of temporal mode. In particular, the two interfering fields may become orthogonal under a modest amount of unbalanced dispersion when the mode number of the fields is $k\geq2$. Moreover, we discuss how to recover the spectrally distorted temporal mode by measuring and compensating the transmission induced dispersion. Our investigation paves the way for further investigating the distribution of temporally multiplexed quantum states in fiber network.