Tristan Kremp

Fast split-step wavelet collocation method for WDM system parameter optimization

To meet rapidly increasing bandwidth requirements, extensive numerical simulations are an important optimization step for optical networks. Using a basis of cardinal functions with compact support, a new split-step wavelet collocation method (SSWCM) was developed as a general solver for the nonlinear Schro/spl uml/dinger equation describing pulse propagation in nonlinear optical fibers. With N as the number of discretization points, this technique has the optimum complexity O(N) for a fixed accuracy, which is superior to the complexity O(Nlog/sub 2/N) of the standard split-step Fourier method (SSFM). For the simulation of a large 40-Gb/s dense-wavelength-division-multiplexing (DWDM) system with 64 channels, the SSWCM requires less than 40% of computation time compared with the SSFM. This improvement allows a systematic optimization of wavelength-division-multiplexing (WDM) system parameters to achieve a minimum bit-error rate.

Continuous Multicore Optical Fiber Grating Arrays for Distributed Sensing Applications

We describe the fabrication and distributed sensing capabilities of very long continuous fiber grating sensor arrays in a twisted multicore fiber. The continuous gratings are fabricated in fibers with UV transparent coating using a flexible and scalable reel-to-reel processing system. Single-frequency continuous gratings are characterized using optical frequency-domain reflectometry and a shape reconstruction algorithm to measure fiber bend radius. Broadband reflection gratings are shown to act as enhanced quasi-Rayleigh scattering elements allowing for distributed temperature measurements in the presence of 10-dB transmission loss.

Fast wavelet collocation method for WDM system parameter optimization

Using a wavelet collocation method, which is substantially faster than the standard split-step Fourier method, accurate optimizations of WDM system parameters become possible. For a typical 40-Gbit/s system, the optimum power level is determined and compared to analytical approximations.

Simulation of two-photon absorption in Raman DFB lasers

We present an efficient split-step solver for the nonlinear coupled mode equations with two-photon absorption to investigate the feasibility of Raman DFB lasers in highly nonlinear materials such as chalcogenide glasses.

A seven core fiber DFB

We demonstrate fiber DFB lasers in a seven core Er doped fiber. DFB grating cavities were fabricated in all cores at once via a single UV exposure. Lasing was observed in all seven cores.

Adaptive Split-Step Quasi-Spectral Finite Difference Method for Nonlinear Optical Pulse Propagation

Combining a new semi-analytical step size estimation strategy with highly efficient quasi-spectral finite differences, a fast adaptive split-step solver for the nonlinear Schrodinger equation is presented. For large WDM systems, a substantial speed-up is obtained.

Analysis of 25+ Meter Long Continuous Distributed Sensor Grating Arrays

An automated analysis of long arrays of distributed sensor gratings in twisted multicore fiber is presented. As an example, we analyze 7×744 quasi-continuous gratings from a single OFDR measurement written through UV transparent coating.

Highly Efficient Distributed Feedback Brillouin Fiber Laser

An efficient single frequency distributed feedback (DFB) Brillouin fiber laser producing 22mW of Stokes output, using 81mW of pump from a semiconductor DFB laser, is shown. The laser operated for a pump frequency detuning >1GHz.

Improving Distributed Sensing with Continuous Gratings in Single and Multi-core Fibers

We review advances in single and multicore continuous fiber grating array sensor technology. Grating enhanced backscattering offers order of magnitude signal improvements for distributed sensing of shape, temperature and strain over lengths up to 1km.

Distributed Feedback Raman and Brillouin Fiber Lasers

Distributed feedback Raman and Brillouin lasers use intrinsic gain mechanisms in optical waveguides to produce compact, narrow-linewidth sources in arbitrary spectral bands determined only by the available pump wavelengths. In this chapter, we begin with a theoretical description of Raman DFB lasers. We show how they can be modeled using a set of nonlinear coupled-mode equations. In agreement with a closed-form approximation to the threshold gain, time domain simulations reveal the dependence of threshold and slope efficiency on cavity parameters such as gain, loss, specifics of the grating profile, and nonlinear effects such as two photon absorption. We then review the realizations of narrow-linewidth Raman fiber lasers. We show how different pump schemes and cavities affect the performance and discuss possibilities for improvements. Finally, we describe the Brillouin DFB laser and compare its performance with that of a Raman DFB laser made with the same cavity.