Different Slow-light systems have been discussed and developed as a powerful tool to reduce the group velocity of optical signals during the last years. It has enjoyed much recent interest because of the potential system applications in optical telecommunication and information systems. Especially the nonlinear effect of stimulated Brillouin scattering (SBS) has become important for fiber based Slow-light systems. But, the SBS also has two challenges. First, the maximum time delay is limited due to the saturation of the Brillouin amplification process and second, the delay of the pulses is accompanied by pulse distortions (pulse shape broadening). For these aspects the shape of the Brillouin spectrum is of special interest. In this article a system is presented which allows the optimisation of the Brillouin spectrum. Simulations and first measurements show how the time delay can be enhanced with a simultaneous reduction of the pulse distortions.
Different Slow-light systems have been discussed and developed as a powerful tool to reduce the group velocity of optical signals during the last years. It has enjoyed much recent interest because of the potential system applications in optical telecommunication and information systems. Especially the nonlinear effect of stimulated Brillouin scattering (SBS) has become important for fiber based Slow-light systems. But, the SBS also has two challenges. First, the maximum time delay is limited due to the saturation of the Brillouin amplification process and second, the delay of the pulses is accompanied by pulse distortions (pulse shape broadening). For these aspects the shape of the Brillouin spectrum is of special interest. In this article a system is presented which allows the optimisation of the Brillouin spectrum. Simulations and first measurements show how the time delay can be enhanced with a simultaneous reduction of the pulse distortions.
Slow- and Fast-Light has been investigated during the last years as a powerful tool to reduce and increase the group velocity of light pulses by light. It has enjoyed much recent interest because of the practical applications for telecommunication and information systems. Among these are optical signal processing, radio frequency-photonics, nonlinear optics and time domain spectroscopy. Furthermore, it can be seen as a key technology for optical delay lines, buffers, equalizers and synchronizers in packet switched networks. For a realization, there are different methods and material systems possible. Among them the nonlinear effect of stimulated Brillouin scattering (SBS) is of special interest. This article gives an overview about the fundamentals and some experimental results of the Slow- and Fast-Light effect based on the SBS in optical fibers.
The manipulation of the group velocity of optical signals (slow and fast light) has many possible applications in telecommunications, sensing, nonlinear optics, and so on. The exploitation of the effect of stimulated Brillouin scattering (SBS) is of special interest for the alteration of the group velocity in optical fibers, since it just requires standard telecom equipment and low-to-moderate optical power. However, each delay in one single, low-gain SBS-based slow-light system is accompanied by a pulse broadening. This is a result of the inherent Kramers–Kronig relations among the gain, the phase change, and the accompanied group velocity. For an ideal flat gain, the phase change is nonideal, and for an ideal phase change the gain curve leads to a broadening. Furthermore, if the gain bandwidth is adapted to the signal by broadening, the delay will be reduced. Thus the signal broadening can be reduced by several methods for one single low-gain slow-light system, but it cannot be zero. Here, we will show how a zero-broadening SBS-based slow light can be achieved with several methods. The basic idea is a reshaping of the original pulse in a second stage by saturation of the SBS system, or by the superposition of two gains. As will be shown, all of these systems show an almost ideal overall gain and phase function over the bandwidth of the pulses. Thus, SBS-based slow light with a delay bandwidth product of 1 bit and zero distortion is possible.
To change the group velocity of optical signals has a lot of possible applications in telecommunications, sensing, nonlinear optics and so on. Especially the exploitation of the effect of stimulated Brillouin scattering (SBS) in optical fibers is of special interest since it just requires standard telecom equipment and low to moderate optical power. However, each delay in one single, low-gain SBS based slow-light system is accompanied by pulse broadening. This is a result of the inherent Kramers-Kronig relations between the gain, the phase-change and the accompanied group velocity. For an ideal flat gain the phase-change is non-ideal, and for an ideal phase-change the gain curve leads to a broadening. Furthermore, if the gain bandwidth is broadened in order to adapt it to the signal, the delay will be reduced. Thus, for one single low-gain slow-light system the broadening can be reduced by several methods but it cannot be zero. Here we will show how a zero-broadening SBS based slow-light system can be achieved by two different methods. The basic idea is a reshaping of the original pulse by an adapted gain in a second stage. This adaptation is achieved by the superposition of two Gaussian gain profiles or by a single saturated gain. As will be shown, these systems show an almost ideal over-all gain and phase function over the bandwidth of the pulses. Thus, SBS based slow-light with a delaybandwidth product of more than 1 bit and zero distortion is possible.
Stimulated Brillouin scattering (SBS) has become a favorable underlying mechanism in many demonstrations of all-optical variable delay in standard fibers, often referred to as slow and fast light. Over 100 journal papers and numerous conference sessions have been dedicated to SBS slow light since 2005. In this paper, recent research in this area is reviewed. Following a short introduction to the topic, several specific trends in contemporary work are highlighted: the optimization of the SBS pump spectrum for extended slow light delay and reduced pulse distortion; SBS slow light demonstrations in nonstandard, highly nonlinear fibers; applications of SBS slow light to the delay of analog waveforms; and the role of polarization. Finally, a brief concluding perspective is provided.
We show a simple method of time delay enhancement in slow-light systems based on the effect of stimulated Brillouin scattering. The method is based on the reduction of the absolute Brillouin gain by a loss produced by an additional pump laser. With this method we achieved pulse delays of nearly 100 ns in a standard single-mode fiber. In the presented approach the delay or acceleration of optical signals is decoupled from their amplification or attenuation, which allows the adaptation of the pulse amplitudes to the given application.
In today's information age demand for ultra-fast information transfer with ultra-high bandwidths has reached extraordinary levels. Hence, the transmission in the future internet-backbone will be increasingly constrained in the network nodes. At the same time, the power consumption of the network systems will increase to unsustainable levels.\nNowadays, optical signal processing and switching can be implemented relatively easily. However, the realization of optical bu ers and short-term memories is still an unsolved challenge. The slow- and fast-light e ect has been investigated as one solution for the optical bu ering over the last few years. It means the slowing down and acceleration of the group velocity of light pulses in a medium. To realize this, many di erent methods and material systems have been developed but due to its signi cant advantages the nonlinear e ect of stimulated Brillouin scattering (SBS) is particularly promising. However, it also su ers from disadvantages which limit the slow- and fast-light performance.