Statistical properties of modal noise in fiber-laser systems

The direct analysis in the time domain of the fluctuations of a signal propagating in a fiber-optic link in the presence of an imperfect connector makes it possible to formalize in a simple manner the description of its statistical properties. This permits, in particular, the clarification of the role played by the various time scales involved in the problem (coherence time of the fiber-exciting source, fiber modal delay, detector response time, etc.) in evaluating the statistical averages. The formalism includes in a straightforward way the case of simultaneous excitation of the fiber by more than one source. This last circumstance is expedient for checking the beneficial effect on modal noise derived from exciting the fiber with N laser sources

Nonlinear interaction of copropagating and counterpropagating waves in straight and highly twisted single-mode fibers

We derive the system of equations describing the nonlinear interaction, associated with the optical Kerr effect, among the four forward- and backward-propagating modes in a straight single-mode fiber. This allows us, in particular, to obtain the set of equations governing nonlinear evolution in a highly twisted fiber of the corresponding copropagating and counterpropagating right and left circularly polarized modes

Laser phase noise to intensity noise conversion by lowest-order group-velocity dispersion in optical fiber: exact theory

An exact result for the spectral density of intensity variations that occur after propagation of ergodic light in a medium having lowest-order-only group-velocity dispersion is obtained and applied to the problem of semiconductor laser phase noise to intensity noise conversion in a single-mode optical fiber. It is shown that the intensity spectrum after propagation formally approaches, for a large laser linewidth or a long (or high-dispersion) fiber, the intensity spectrum of a thermal source having the same line shape as the laser

Time-dependent analysis of a fiber-optic passive-loop resonator

A time-dependent analysis of an all-single-mode fiber-optic resonator is presented in which the input field is allowed to exhibit an arbitrary dependence on time. In particular, the transmissivity of the resonator is evaluated for an input field possessing an arbitrary temporal coherence, which allows one to consider the role of the source coherence time as compared with the fiber time delay

Propagation and stability of optical pulses in a diffractive dispersive non-linear medium

Propagation and stability of light pulses under the combined influence of the optical Kerr effect, dispersion and diffraction are investigated by adopting a variational procedure. In particular, it is found that 'light bullets', i.e. radially symmetric pulses propagating without distortion, are not necessarily unstable under perturbations which do not maintain radial symmetry

Coherence and Efficiency in Nonlinear Optical Processes

A remarkable difference between linear and nonlinear processes lies in the fact that the efficiency of the latter depends on the coherence properties of the electromagnetic field (pump) from which the process is driven

Built-in reduction of statistical fluctuations of partitioning objects

Our theoretical and numerical investigation of the movement of an object that partitions a microtubule filled with small particles indicates that vibrations warranted by thermal equilibrium are reached only after a time that increases exponentially with the number of particles involved. This points to a basic mechanical process capable of breaching, on accessible time scales, the ultimate ergodic constraints that force randomness on bound microscale and nanoscale systems

Influence of chromatic dispersion on degenerate four-wave mixing

We investigate the way in which four-wave mixing in a waveguide is affected by chromatic dispersion. The frequency dependence of the associated phase-conjugate mirror reflectivity turns out not to be influenced by chromatic dispersion itself