Nonlinearity measurement undergoing dispersion and loss.

Accurate knowledge of the nonlinear coefficient is extremely important to make reliable predictions about optical pulses propagating along waveguides. Nevertheless, determining this parameter when dispersion and loss are as important as nonlinear effects brings both theoretical and experimental challenges that have not yet been solved. A general method for measuring the nonlinear coefficient of waveguides under these demanding conditions is here derived and demonstrated experimentally in a kilometer-long standard silica fiber pumped close to 2 µm.

Doubly active Q switching and mode locking of an all-fiber laser.

Simultaneous and independent active Q switching and active mode locking of an erbium-doped fiber laser is demonstrated using all-fiber modulation techniques. A magnetostrictive rod attached to the output fiber Bragg grating modulates the Q factor of the Fabry-Perot cavity, whereas active mode locking is achieved by amplitude modulation with a Bragg-grating-based acousto-optic device. Fully modulated Q-switched mode-locked trains of optical pulses were obtained for a wide range of pump powers and repetition rates. For a Q-switched repetition rate of 500 Hz and a pump power of 100 mW, the laser generates trains of 12-14 mode-locked pulses of about 1 ns each, within an envelope of 550 ns, an overall energy of 0.65 microJ, and a peak power higher than 250 W for the central pulses of the train.

Dual random phase encoding: a temporal approach for fiber optic applications.

We analyze the dual random phase encoding technique in the temporal domain to evaluate its potential application for secure data transmission in fiber optic links. To take into account the optical fiber multiplexing capabilities, the noise content of the signal is restricted when multiple channels are transmitted over a single fiber optic link. We also discuss some mechanisms for producing encoded time-limited as well as bandwidth-limited signals and a comparison with another recently proposed technique is made. Numerical simulations have been carried out to analyze the system performance. The results indicate that this multiplexing encryption method could be a good alternative compared with other well-established methods.

Time-variant signal encryption by lensless dual random phase encoding applied to fiber optic links.

A lensless dual random phase encoding technique in the temporal domain is proposed and analyzed to evaluate its potential application for secure data transmission, mainly for short-haul fiber optic links. The different signal broadening effects produced by each stage of the encoding process in both time and frequency domains are analyzed by using the Wigner distribution function to take into account the fiber's multiplexing capabilities. Thus, quasi-white noise with a well-defined bandwidth is used in the encoding process to limit the bandwidth of the encrypted signal. Numerical simulations revealed good system performance, indicating that this multiplexing encryption method could be a good alternative to other well-established techniques.

Temporal filtering for Montgomery self-imaging under dispersive transmission.

We present what we believe is a new method to introduce self-imaging properties under dispersive transmission of single or multiple light pulses with different temporal characteristics. By properly performing a temporal filtering into a given input signal it can produce an output signal having a spectral content satisfying the Montgomery condition, thereby allowing self-imaging of this signal under further dispersive transmission. An array of fiber loops performs the filtering operation on the input signal. We show some numerical simulations with a single light pulse as an input signal to verify the feasibility of the method and demonstrate the effects of the several involved parameters on both the pulse shape and the noise level.