Miguel González Herráez

Observation of pulse delaying and advancement in optical fibers using stimulated Brillouin scattering

We demonstrate experimentally that it is possible to control optically the group velocity of an optical pulse as it travels along an optical fiber. To achieve this control we use the effect of Stimulated Brillouin Scattering. In our experiments we have achieved changes in the group index of 10-3 in several kilometer-length fibers, thus leading to pulse delaying and advancement in the range of tens of nanoseconds. We believe that this is the first evidence of such optically-controlled strong delay changes in optical fibers. In this paper we derive the basic theory behind these group-delay changes and we demonstrate the effect in two kinds of fibers which are conventionally used.

Arbitrary-bandwidth Brillouin slow light in optical fibers

Brillouin slow light in optical fibers is a promising technique for the development of all-optical buffers to be used in optical routers. The main drawback of this technique up to now has been its narrow bandwidth, normally restricted to 35 MHz in conventional single-mode optical fibers. In this paper we demonstrate experimentally that Brillouin slow light with an arbitrary large bandwidth can be readily obtained in conventional optical fibers using a simple and inexpensive pump spectral broadening technique. In our experiments, we show the delaying of 2.7 ns pulses over slightly more than one pulse length with only some residual broadening (<25%) of the pulse width. We see no limit to extend this technique to the delaying of GHz-bandwidth signals.

Long optically controlled delays in optical fibers

Optically controlled delay lines in optical fibers are demonstrated by use of the group-velocity control of signal pulses based on stimulated Brillouin scattering. We achieve continuous time delay within the range of 150 ns, much larger than the width of the 40 ns signal pulse, using cascaded fiber segments joined by unidirectional optical attenuators. In the meantime, we also observe a large amount of pulse broadening, which agrees well with a theoretical prediction based on linear theory.

Highly efficient Brillouin slow and fast light using As 2 Se 3 chalcogenide fiber

We demonstrate the generation of slow and fast light based on stimulated Brillouin scattering in As(2)Se(3) chalcogenide fiber with the best efficiency ever reported. The Brillouin gain of 43 dB is achieved with only 60-mW pump power in a 5-m single-mode chalcogenide fiber, which leads to the optical time delay of 37 ns with a 50-ns Gaussian pulse.

Gain-assisted pulse advancement using single and double Brillouin gain peaks in optical fibers

We report the first experimental demonstration of pulse advancement with gain in optical fibers based on stimulated Brillouin scattering. Two experimental configurations are investigated and compared. One is to make the pulse propagate in a region slightly detuned from a gain peak where the group velocity change is negative and the other is to make use of the large anomalous dispersion appearing between two gain peaks. We experimentally show that the second method produces pulse advancement with lower distortion than the first one.

Detrimental effect of modulation instability on distributed optical fiber sensors using stimulated Brillouin scattering

Modulation instability can limit the resolution and the range of distributed fibre sensors based on stimulated Brillouin scattering. In this paper we analyse this process and suggest adequate methods to overcome it.

Distributed measurement of chromatic dispersion by four-wave mixing and Brillouin optical-time-domain analysis

A new nondestructive method for measuring the spatial distribution of chromatic dispersion along an optical fiber is presented. It is based on using Brillouin optical time-domain analysis to probe the power distribution of the four-wave mixing generated by two continuous-wave lasers. The results obtained prove that this new method is capable of providing better performance than comparable techniques. Furthermore, sensing the variations of Brillouin gain maximum produces additional information about the fiber, such as presence of strain and concentration of GeO2.

Brillouin distributed fibre sensing using phase modulated probe

A novel configuration for a Brillouin distributed sensor using a phase modulated probe is presented. It offers the combined advantages of a direct implementation using simple devices and a large immunity to noise, shifting the information from the baseband to a higher frequency, which substantially strengthens the robustness to perturbations, interferences and other optical coherent noises. It naturally facilitates the possibility to perform frequency-coding on the probe to realise dynamic and fast measurements, since all frequency tunings are realised at sub-GHz frequencies.

Mapping of chromatic-dispersion distribution along optical fibers with 20-m spatial resolution

The accurate mapping of chromatic-dispersion distribution along single-mode optical fibers with the best spatial resolution ever reported is experimentally demonstrated. The method consists of a new way of probing four-wave-mixing (FWM) efficiency along the fiber using Brillouin-optical-time-domain analysis (BOTDA). The new setup eliminates many noise problems found in previous configurations, allowing a tenfold improvement in the spatial resolution of this kind of measurements. Resolutions of 20 m in a 1.1-km standard fiber and 150 m in a 6.7-km dispersion-shifted fiber (DSF), respectively, were achieved.

Chromatic dispersion mapping by sensing the power distribution of four-wave mixing along the fiber using Brillouin probing

A new method for chromatic dispersion mapping in optical fibers is presented. It is based on measuring the CW four-wave mixing distribution created by two beams along the fiber using a Brillouin-OTDA. Experimental results demonstrate the feasibility of the technique.