Brillouin Slow Light Research Articles

Enhanced sensitivity temperature sensing based on second order Brillouin slow light

We demonstrate a temperature fiber sensor with enhanced sensitivity based on the second order Brillouin slow light. In this process, the modulated probe wave coincides with the second order Brillouin gain that was generated by circulating the first order Brillouin Stokes signal. Optical delay was induced on the modulated probe wave as it interacts with the second order Brillouin Stokes signal. As the temperature changes, the measured optical delay at the output also changes accordingly. The first order setup has a temperature slope coefficient of 1.126 ns/°C. Compared to the first order setup, the second order setup achieved a coefficient of 1.917 ns/°C, which is almost double the value obtained from the first order experiment.

Enhanced sensitivity of fiber laser sensor with Brillouin slow light.

We proposed and experimentally demonstrated a new scheme for enhancing the sensitivity of a fiber laser sensor using Brillouin slow light. The Brillouin laser was exposed to environmental vibrations, producing fluctuations at 408 kHz frequency, which were then interrogated using a Mach-Zehnder interferometer. By introducing Brillouin slow light into one arm of the interferometer, the sensitivity increased by 1.57 times that of a device without slow light. We believe this scheme may provide a new way of using Brillouin slow light and that it has some important implications regarding the use of fiber sensors for measuring the vibration, temperature, strain and so on.

Brillouin slow light: substantial optical delay in the second-order Brillouin gain spectrum.

We experimentally demonstrate optical delay in the second-order Brillouin gain spectrum by incorporating a double Brillouin-frequency shifter into the system. By coinciding the seed signal with the second-order Brillouin gain spectrum, it was found that the seed signal experienced significantly larger delay as compared to the Brillouin slow light generated from the first-order Brillouin spectrum. At a Brillouin gain of 17 dB, the delay was found to be at maximum of 60 ns. This widens the window of promising opportunities into the deployment of all optical tunable delay into the existing optical signal processing.

Multi-Channel Broadband Brillouin Slow Light With Multiple Longitudinal Mode Pump

Independent delay control of multi-channel signals based on stimulated Brillouin scattering slow light is proposed and demonstrated for the first time by using a multiple longitudinal mode fiber laser. Two independent broadband Brillouin pumps are generated by a fiber ring laser, which use a semiconductor optical amplifier as gain medium. The spectrum of each pump is comprised of a large number of longitudinal lasing modes, separated by 7 MHz and spanning a bandwidth of 11.6 and 11.2 GHz, respectively. The multi-channel broadband Brillouin slow light is demonstrated by using 8 Gb/s data signals. The signals in both channels are continuously delayed by as much as 80 ps at 21 dBm pump power, and the maximal delay-time with error free operation (bit error rate <; 10-9) are up to 56.4 and 56 ps at 19 dBm pump power.

Broadband Brillouin slow light with multiple-longitudinal-mode, tunable pump

We propose and demonstrate broadband Brillouin slow light using a multiple-longitudinal-mode tunable fiber laser as Brillouin pump. A tunable broadband Brillouin pump with a tuning range from 1 520 to 1 555 nm is generated using a fiber ring laser with a semiconductor optical amplifier (SOA) as its gain medium. The pump spectrum consists of a large number of longitudinal modes separated by 6 MHz. The 3-dB bandwidth is about 11.5 GHz, and its fluctuation is less than 100 MHz within the tuning range. An 8-Gb/s data signal can be delayed by up to 83.0 ps (bit error rate < 10?9) at 17-dBm pump power.

Optical monitoring of gas supply systems in metropolitan area

A novel fiber optic sensor system to monitor the gas pipeline network designed for PGNiG, Polish oil and gas exploration and production company is presented. The system is based on standard telecommunication fibers and devices, except for user-oriented and specially designed intensity-based optical sensors that utilize fiber macro- and microbending effects. Laboratory tests showed that the system is simple, easy to install, reliable, and fulfils the user requirements. Full Text: PDF References L. Zou, G. Ferrier, S. Afshar, Q. Yu, L. Chen, X. Bao,"Distributed Brillouin Scattering Sensor for Discrimination of Wall-Thinning Defects in Steel Pipe under Internal Pressure", App. Opt. 43, 1583 (2004) [CrossRef] L. Zou, X. Bao, S. Yang, L. Chen, F. Ravet,"Effect of Brillouin slow light on distributed Brillouin fiber sensors", Opt. Lett. 31, 2698 (2006) [CrossRef] D. Marcuse,"Microdeformation losses of single-mode fibers", Appl. Opt. 23, 1082 (1984) [CrossRef] R. Olshansky,"Distortion losses in cabled optical fibers", Appl. Opt. 14, 20 (1975) A.W. Domański, T. Poczęsny, K. Prokopczuk, P. Makowski,"An optical fiber loop sensor for vibration monitoring", Phot. Lett. Poland 2(2), 58 (2010) T. Poczęsny, K. Prokopczuk, P. Makowski, A.W. Domański,"Optical fiber macro-bend seismic sensor for real-time vibration monitoring in harsh industrial environment", Proc. SPIE 8082, 80823L (2011) [CrossRef] K. Prokopczuk, T. Poczęsny, A.W. Domański,"Multi-point vibration sensor using a fiber optic telecommunication cable", Proc. SPIE 8010, 80100E (2011) [CrossRef]

Influence of third-order dispersion on delay performance in broadband Brillouin slow light: erratum

We investigate theoretically the delay performance of Brillouin slow light employing a broadband pump with a rectangular spectrum. Analytical expression of delayed Gaussian pulse amplitude is deduced with the second-order gain nonuniformity and the stimulated-Brillouin scattering-induced third-order dispersion effects involved. Calculated results show that the Gaussian pulse with full-width at half maximum of 200 ps is delayed by 80 ps with little pulse broadening in a single-stage Brillouin slow-light medium, and the time delay is extended to multi-hundred ps with low distortion in a cascaded Brillouin slow-light system. Comparing the analytical results with the numerical ones, we confirm that the pulse distortion is mainly attributed to the large third-order dispersion introduced by stimulated-Brillouin scattering.

Analysis of pulse distortion in Brillouin slow light using broadband pump with rectangular spectrum

Assuming a Gaussian-shaped input signal pulse, we deduced the analytical expression of the output-pulse amplitude envelope in the Brillouin slow light system utilizing broadband pump with a rectangular spectrum under small-signal gain approximation. The expression is applicable in case that the pump spectrum has a sharp rising or trailing edge and a flat top. The influence of the fiber dispersion, the stimulated Brilouin scattering (SBS) gain non-uniformity and the SBS-gain-induced dispersion on the pulse distortion has also been quantitatively analyzed. The calculated results show that the analytical solution agrees well with the numerical one if the spectrum of the signal pulse lies in the pump spectrum. SBS-gain-induced third-order dispersion is the main physical factor responsible for the pulse distortion, which also limits the retardation increase of the short pulse in the cascaded Brillouin slow light system.

Influence of third-order dispersion on delay performance in broadband Brillouin slow light

We investigate theoretically the delay performance of Brillouin slow light employing a broadband pump with a rectangular spectrum. Analytical expression of delayed Gaussian pulse amplitude is deduced with the second-order gain nonuniformity and the stimulated-Brillouin scattering-induced third-order dispersion effects involved. Calculated results show that the Gaussian pulse with full-width at half maximum of 200 ps is delayed by 80 ps with little pulse broadening in a single-stage Brillouin slow-light medium, and the time delay is extended to multi-hundred ps with low distortion in a cascaded Brillouin slow-light system. Comparing the analytical results with the numerical ones, we confirm that the pulse distortion is mainly attributed to the large third-order dispersion introduced by stimulated-Brillouin scattering.

Effects of Brillouin slow light on intensity-modulated waveforms in optical fibers

We demonstrate a theoretical analysis and the experimental confirmation of the effects of Brillouin slow light on intensity-modulated waveforms in optical fibers. The results show that the DC and the AC parts of the waveform experience different Brillouin gain according to the modulation frequency, and the time delay of the intensity-modulated signal can be used to directly measure the phase-index change of the slow light configuration.

Broadband Brillouin slow light based on multifrequency phase modulation in optical fibers

We theoretically analyze and experimentally demonstrate broadband Brillouin slow light using multiple equal-amplitude spectral lines generated by multifrequency phase modulation. The theoretical analysis shows that 4n−1 equal-amplitude spectral lines can be obtained if the modulation signal comprises the fundamental frequency and the odd harmonic waves, where n denotes the number of frequency components in the modulation signal. In experiment, 7 and 11 equal-amplitude spectral lines are obtained and Brillouin bandwidths of 340 and 570 MHz are gained, respectively. The experimental results also indicate that the slope of the broadening factor for the delayed signal decreases in the case of broad and flattened Brillouin gain spectrum.

Numerical Modeling of Zero-Gain Brillouin Slow Light in a Tellurite Fiber

We investigate numerically zero-gain Brillouin slow light in a single mode tellurite fiber. The effects of the bandwidth ratio β between the loss and gain on the pulse delay and widening are discussed in detail. Our simulated results show that, the time delay in 200 m long tellurite fiber can reach 255 ns and the corresponding widening factor of the input pulse (pulse width ∼ 20 ns) is less than 3 when the pump power is fixed at 1194.6 mW and β=10. The limitation of zero-gain slow light system is also discussed.

Effect of Brillouin slow light on distributed Brillouin fiber sensors

The effect of Brillouin slow light on distributed Brillouin fiber sensors (DBFSs) is studied. We demonstrate Brillouin slow light for a 1.2 ns pulse with peak powers (PS) from 3.3 to 56.2 mW on depletion of the pump power (PP) ranging from 1.3 to 83.2 mW in conventional optical fibers (SMF-28). Experiments show that, when pump power depletion is not negligible, for a given PP the Brillouin gain and delay time of a pulse decrease when PS increases in a long (> or =10 km) sensing fiber. The optimum pump beam depletion resulting from strong interaction of the pump and the probe in the fiber provides accurate temperature and strain information at a high spatial resolution. Our study reveals that at low PP the spatial resolution error caused by the pulse delay for a DBFS with centimeter spatial resolution is less than 5% of the pulse length.

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.

Theoretical study of the effect of slow light on BOTDA spatial resolution

Due to the resonant nature of Brillouin scattering, delay occurs while pulse is propagating in an optical fiber. This effect influences the location accuracy of distributed Brillouin sensors. The maximum delay in sensing fibers depends on length, position, pump and Stokes powers. Considering pump depletion, we have obtained integral solutions for the coupled amplitude equations under steady state conditions and then calculated the group delay. The results show that moderate pump depletion (which is the optimized sensor working range) mitigates significantly the delay, and the maximum delay induced at resonance is only a fraction of Brillouin Optical Time Domain (BOTDA) spatial resolution, which means that the use of pulse width to define the spatial resolution is valid when Brillouin slow light is considered. We have shown that uniform strain and temperature distribution in a fiber gives the maximum delay induced uncertainty.

Tunable All-Optical Delays via Brillouin Slow Light in an Optical Fiber

We demonstrate a technique for generating tunable all-optical delays in room temperature single-mode optical fibers at telecommunication wavelengths using the stimulated Brillouin scattering process. This technique makes use of the rapid variation of the refractive index that occurs in the vicinity of the Brillouin gain feature. The wavelength at which the induced delay occurs is broadly tunable by controlling the wavelength of the laser pumping the process, and the magnitude of the delay can be tuned continuously by as much as 25 ns by adjusting the intensity of the pump field. The technique can be applied to pulses as short as 15 ns. This scheme represents an important first step towards implementing slow-light techniques for various applications including buffering in telecommunication systems.