Myungjun Lee

Improved slow-light delay performance of a broadband stimulated Brillouin scattering system using fiber Bragg gratings

We present a technique for improving the pulse-delay performance of a stimulated Brillouin scattering (SBS) based broadband slow-light system by combining it with fiber Bragg gratings (FBG). We optimize the physical device parameters of three systems: (1) broadband SBS, (2) broadband SBS + a single FBG, and (3) broadband SBS + a double FBG for maximizing the delay performance. The optimization is performed under distortion and system resource constraints for a range of bit rates from 0.5 to 8.5 Gbps. We find that an optimized broadband SBS + a double FBG system improves the fractional delay 1.8 times that of the broadband SBS system at an optimum bit rate of 3 Gbps. Also, pump power consumption is reduced by 15% as compared to the broadband SBS system at the same bit rate.

High-fidelity, broadband stimulated-Brillouin-scattering-based slow light using fast noise modulation

We demonstrate a 5-GHz-broadband tunable slow-light device based on stimulated Brillouin scattering in a standard highly-nonlinear optical fiber pumped by a noise-current-modulated laser beam. The noisemodulation waveform uses an optimized pseudo-random distribution of the laser drive voltage to obtain an optimal flat-topped gain profile, which minimizes the pulse distortion and maximizes pulse delay for a given pump power. In comparison with a previous slow-modulation method, eye-diagram and signal-to-noise ratio (SNR) analysis show that this broadband slow-light technique significantly increases the fidelity of a delayed data sequence, while maintaining the delay performance. A fractional delay of 0.81 with a SNR of 5.2 is achieved at the pump power of 350 mW using a 2-km-long highly nonlinear fiber with the fast noise-modulation method, demonstrating a 50% increase in eye-opening and a 36% increase in SNR in the comparison.

Information theoretic framework for the analysis of a slow-light delay device

We present a framework for the information theoretic analysis of slow-light devices. We employ a model in which the device input is a binary-valued data sequence and the device output is considered within a window of finite duration. We use the mutual information between these two quantities to measure information content. This approach enables the information theoretic definitions of delay and throughput. We use our new framework to analyze a delay device based on stimulated Brillouin scattering (SBS) and find good agreement with previous SBS delay bounds.

Information-theoretic analysis of a stimulated-Brillouin-scattering-based slow-light system

We use an information-theoretic method developed by Neifeld and Lee [J. Opt. Soc. Am. A 25, C31 (2008)] to analyze the performance of a slow-light system. Slow-light is realized in this system via stimulated Brillouin scattering in a 2 km-long, room-temperature, highly nonlinear fiber pumped by a laser whose spectrum is tailored and broadened to 5 GHz. We compute the information throughput (IT), which quantifies the fraction of information transferred from the source to the receiver and the information delay (ID), which quantifies the delay of a data stream at which the information transfer is largest, for a range of experimental parameters. We also measure the eye-opening (EO) and signal-to-noise ratio (SNR) of the transmitted data stream and find that they scale in a similar fashion to the information-theoretic method. Our experimental findings are compared to a model of the slow-light system that accounts for all pertinent noise sources in the system as well as data-pulse distortion due to the filtering effect of the SBS process. The agreement between our observations and the predictions of our model is very good. Furthermore, we compare measurements of the IT for an optimal flattop gain profile and for a Gaussian-shaped gain profile. For a given pump-beam power, we find that the optimal profile gives a 36% larger ID and somewhat higher IT compared to the Gaussian profile. Specifically, the optimal (Gaussian) profile produces a fractional slow-light ID of 0.94 (0.69) and an IT of 0.86 (0.86) at a pump-beam power of 450 mW and a data rate of 2.5 Gbps. Thus, the optimal profile better utilizes the available pump-beam power, which is often a valuable resource in a system design.

Systematic design study of an all-optical delay line based on Brillouin scattering enhanced cascade coupled ring resonators

We present a technique to improve the slow-light performance of a side-coupled integrated spaced sequence of resonators?(SCISSOR) combined with a stimulated Brillouin scattering?(SBS) gain medium in optical fibers. We evaluate device performance of SCISSOR-only and SCISSOR + SBS systems for different numbers of cascaded resonators from 1 to 70 using two different data fidelity metrics including eye-opening and mutual information. A practical system design is demonstrated by analyzing its performance in terms of fractional delay, power transmission, and data fidelity. We observe that the results from the two metrics are in good agreement. Based on system optimization under practical resource and fidelity constraints, the SCISSOR consisting of 70 cascaded resonators provides a fractional delay of ~ 8 with 22?dB attenuation at a signal bit rate of 10?Gbps. The combined optimal SCISSOR (with?70?resonators) + SBS system provides a improved fractional delay up to ~ 17 with unit power transmission under the same constraints.

Information theoretic analysis of a slow-light channel

We present a new formalism for the analysis of a slow-light channel, which enables natural information-theoretic definitions for delay and capacity. We apply this formalism to a simple gain-based delay system.

Enhanced slow-light effect by combining broadband SBS system and off-resonance FBG

We present a technique for improving the pulse-delay performance of stimulated Brillouin scattering (SBS) based slow-light system by combining it with a fiber Bragg grating (FBG) under distortion and system resource constraints.

Using a Fabry-Perot to Reduce Distortion in a Gain-Based Delay System

We present a technique for simultaneously increasing the gain-based slow light pulse delay and reducing the distortion by combining a Lorentzian gain line system and a component Fabry-Perot (FP).