Mode scrambler

About: Mode scrambler is a research topic. Over the lifetime, 896 publications have been published within this topic receiving 13595 citations.

Quantitative characterization of higher-order mode converters in weakly multimoded fibers.

Abstract: We present a rigorous analysis methodology of fundamental to higher order mode converters in step index few mode optical fibers. We demonstrate experimental conversion from a fundamental LP01 mode to the higher order LP11 mode utilizing a multiple mechanical bend mode converter.We perform a quantitative analysis of the measured light intensity, and demonstrate a modal decomposition algorithm to characterize the modal content excited in the fiber. Theoretical modelling of the current mode converter is then performed and compared with experimental findings.

Thermally induced mode distortion and its limit to power scaling of fiber lasers

Abstract: A general model is proposed to describe thermal-induced mode distortion in the step-index fiber (SIF) high power lasers. Two normalized parameters in the model are able to determine the mode characteristic in the heated SIFs completely. Shrinking of the mode fields and excitation of the high-order modes by the thermal-optic effect are investigated. A simplified power amplification model is used to describe the output power redistribution under various guiding modes. The results suggest that fiber with large mode area is more sensitive on the thermally induced mode distortion and hence is disadvantaged in keeping the beam quality in high power operation. The model is further applied to improve the power scaling analysis of Yb-doped fiber lasers. Here the thermal effect is considered to couple with the optical damage and the stimulated Raman scattering dynamically, whereas direct constraint from the thermal lens is relaxed. The resulting maximal output power is from 67kW to 97kW, depending on power fraction of the fundamental mode.

Observation of externally controlled mode coupling in optical waveguides

Abstract: Externally controlled mode coupling was observed in a 0.7-km optical waveguide fiber resulting in a significant pulse narrowing. The method of mode coupling generation requires that care be exercised in any mode coupling measurement. Observations on a 3-km waveguide failed to show evidence of mode coupling, allowing the possibility of practical external control.

Mode Control in a Multimode Fiber Through Acquiring its Transmission Matrix from a Reference-less Optical System

Abstract: A simple imaging system together with complex semidefinite programming is used to generate the transmission matrix of a multimode fiber. Once the transmission matrix is acquired, we can modulate the phase of the input signal to induce strong mode interference at the fiber output. The optical design does not contain a reference arm and no interferometric measurements are required. We use a phase-only spatial light modulator to shape the profile of the propagating modes and the output intensity at an individual pixel is monitored. The semidefinite program uses a convex optimization algorithm to generate the transmission matrix of the optical system using intensity only measurements. This simple yet powerful method can be used to compensate for modal dispersion in multimode fiber communication systems. It also yields great promises for the next generation biomedical imaging, quantum communication, and cryptography.

Mode scrambler for optical fibers.

Abstract: Mode conversion at a splice was measured. Even the best splice, whose transmission loss was less than 0.01 dB, caused a mode conversion equaling about 11% of the total power. Spliced fiber transmission characteristics were influenced by the splicing conditions. To avoid deviations in characteristics due to splices a simple and effective mode scrambler was fabricated. Its insertion loss was less than 0.3 dB for a laser diode. Each mode’s output waveform was found to be the same as the total output waveform.