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Optics Express

Optics Express

  • Editor: Andrew M. Weiner
  • Vol. 22, Iss. 6 — Mar. 24, 2014
  • pp: 6453–6463
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High-resolution long-reach distributed Brillouin sensing based on combined time-domain and correlation-domain analysis

David Elooz, Yair Antman, Nadav Levanon, and Avi Zadok  »View Author Affiliations


Optics Express, Vol. 22, Issue 6, pp. 6453-6463 (2014)
http://dx.doi.org/10.1364/OE.22.006453


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Abstract

A new scheme for distributed Brillouin sensing of strain and temperature in optical fibers is proposed, analyzed and demonstrated experimentally. The technique combines between time-domain and correlation-domain analysis. Both Brillouin pump and signal waves are repeatedly co-modulated by a relatively short, high-rate phase sequence, which introduces Brillouin interactions in a large number of discrete correlation peaks. In addition, the pump wave is also modulated by a single amplitude pulse, which leads to a temporal separation between the generation of different peaks. The Brillouin amplification of the signal wave at individual peak locations is resolved in the time domain. The technique provides the high spatial resolution and long range of unambiguous measurement offered by correlation-domain Brillouin analysis, together with reduced acquisition time through the simultaneous interrogation of a large number of resolution points. In addition, perfect Golomb codes are used in the phase modulation of the two waves instead of random sequences, in order to reduce noise due to residual, off-peak Brillouin interactions. The principle of the method is supported by extensive numerical simulations. Using the proposed scheme, the Brillouin gain spectrum is mapped experimentally along a 400 m-long fiber under test with a spatial resolution of 2 cm, or 20,000 resolution points, with only 127 scans per choice of frequency offset between pump and signal. Compared with corresponding phase-coded, Brillouin correlation domain analysis schemes with equal range and resolution, the acquisition time is reduced by a factor of over 150. A 5 cm-long hot spot, located towards the output end of the pump wave, is properly identified in the measurements. The method represents a significant advance towards practical high-resolution and long range Brillouin sensing systems.

© 2014 Optical Society of America

1. Introduction

Stimulated Brillouin Scattering (SBS) is a non-linear effect which can couple between two optical waves along standard optical fibers [1

1. R. W. Boyd, Nonlinear Optics, 3rd ed. (Academic, 2008).

]. In SBS, a relatively intense pump wave interacts with a counter-propagating, typically weaker signal wave, which is detuned in frequency [1

1. R. W. Boyd, Nonlinear Optics, 3rd ed. (Academic, 2008).

]. The combination of the two waves generates a slowly-traveling intensity wave whose frequency equals the difference between the frequencies of the pump and signal waves, and its wavenumber is the sum of their wavenumbers. Through electrostriction, the intensity wave introduces traveling density variations, namely an acoustic wave, which in turn leads to a traveling grating of refractive index variations due to the photo-elastic effect. The traveling grating can couple optical power between the counter-propagating pump and signal waves. Effective coupling, however, requires that the difference between the two optical frequencies should closely match a particular, fiber-dependent value known as the Brillouin frequency shift νB ~11 GHz (for standard single mode fibers at ~1550 nm wavelength). The power of a signal wave whose optical frequency is νB below that of the pump is amplified by SBS. The amplification bandwidth achieved with continuous-wave (CW) pumping is rather narrow: on the order of 30 MHz, as dictated by the relatively long lifetime of acoustic phonons [1

1. R. W. Boyd, Nonlinear Optics, 3rd ed. (Academic, 2008).

, 2

2. A. Zadok, A. Eyal, and M. Tur, “Stimulated Brillouin scattering slow light in optical fibers [Invited],” Appl. Opt. 50(25), E38–E49 (2011). [CrossRef]

].

The value of νB varies with both temperature and mechanical strain [3

3. T. Kurashima, T. Horiguchi, and M. Tateda, “Distributed-temperature sensing using stimulated Brillouin scattering in optical silica fibers,” Opt. Lett. 15(18), 1038–1040 (1990). [CrossRef] [PubMed]

]. Hence, a mapping of the local Brillouin gain spectrum along standard fibers is being used in distributed sensing of both quantities for 25 years [4

4. T. Horiguchi, T. Kurashima, and M. Tateda, “A technique to measure distributed strain in optical fibers,” IEEE Photonics Technol. Lett. 2(5), 352–354 (1990). [CrossRef]

6

6. X. Bao and L. A. Chen, “Recent progress in Brillouin scattering based fiber sensors,” Sensors (Basel) 11(4), 4152–4187 (2011). [CrossRef] [PubMed]

]. The most widely employed configuration for such measurements is known as Brillouin optical time domain analysis (B-OTDA), in which pump pulses are used to amplify CW signals and the output signal power is monitored as a function of time [4

4. T. Horiguchi, T. Kurashima, and M. Tateda, “A technique to measure distributed strain in optical fibers,” IEEE Photonics Technol. Lett. 2(5), 352–354 (1990). [CrossRef]

]. Experiments are repeated for a range of frequency offsets ν ~νB between pump and signal. The measurement range of B-OTDAs could reach 100 km [7

7. S. Martin-Lopez, M. Alcon-Camas, F. Rodriguez, P. Corredera, J. D. Ania-Castañon, L. Thévenaz, and M. Gonzalez-Herraez, “Brillouin optical time-domain analysis assisted by second-order Raman amplification,” Opt. Express 18(18), 18769–18778 (2010). [CrossRef] [PubMed]

10

10. Y. Dong, L. Chen, and X. Bao, “Time-division multiplexing-based BOTDA over 100 km sensing length,” Opt. Lett. 36(2), 277–279 (2011). [CrossRef] [PubMed]

], and they are capable, at least in principle, of mapping the SBS gain for a given ν along the entire fiber with just a single scan. The acquisition times of B-OTDA setups were recently reduced to the order of ms for 100 m-long fibers [11

11. Y. Peled, A. Motil, L. Yaron, and M. Tur, “Slope-assisted fast distributed sensing in optical fibers with arbitrary Brillouin profile,” Opt. Express 19(21), 19845–19854 (2011). [CrossRef] [PubMed]

13

13. Y. Peled, A. Motil, I. Kressel, and M. Tur, “Monitoring the propagation of mechanical waves using an optical fiber distributed and dynamic strain sensor based on BOTDA,” Opt. Express 21(9), 10697–10705 (2013). [CrossRef] [PubMed]

]. However, the duration of pulses in the fundamental B-OTDA scheme is restricted to the acoustic lifetime τ ~5 ns or longer, which corresponds to a spatial resolution limitation on the order of 1 m [14

14. A. Fellay, L. Thevenaz, M. Facchini, M. Nikles, and P. Robert, “Distributed sensing using stimulated Brillouin scattering: towards ultimate resolution,” in 12th International Conference on Optical Fiber Sensors, Vol. 16 of 1997 OSA Technical Digest Series (Optical Society of America, 1997), paper OWD3.

]. Numerous schemes had been proposed in recent years for resolution enhancement in B-OTDA [6

6. X. Bao and L. A. Chen, “Recent progress in Brillouin scattering based fiber sensors,” Sensors (Basel) 11(4), 4152–4187 (2011). [CrossRef] [PubMed]

,15

15. J. C. Beugnot, M. Tur, S. F. Mafang, and L. Thévenaz, “Distributed Brillouin sensing with sub-meter spatial resolution: modeling and processing,” Opt. Express 19(8), 7381–7397 (2011). [CrossRef] [PubMed]

], such as the pre-excitation of the acoustic wave [16

16. V. Lecoeuche, D. J. Webb, C. N. Pannell, and D. A. Jackson, “Transient response in high-resolution Brillouin-based distributed sensing using probe pulses shorter than the acoustic relaxation time,” Opt. Lett. 25(3), 156–158 (2000). [CrossRef] [PubMed]

,17

17. F. Wang, X. Bao, L. Chen, Y. Li, J. Snoddy, and X. Zhang, “Using pulse with a dark base to achieve high spatial and frequency resolution for the distributed Brillouin sensor,” Opt. Lett. 33(22), 2707–2709 (2008). [CrossRef] [PubMed]

], dark [18

18. A. W. Brown, B. G. Colpitts, and K. Brown, “Distributed sensor based on dark-pulse Brillouin scattering,” IEEE Photonics Technol. Lett. 17(7), 1501–1503 (2005). [CrossRef]

] and π-phase [19

19. L. Thévenaz and S. F. Mafang, “Distributed fiber sensing using Brillouin echoes,” Proc. SPIE 7004, 70043N (2008).

,20

20. S. Foaleng Mafang, M. Tur, J. C. Beugnot, and L. Thevenaz, “High spatial and spectral resolution long-range sensing using Brillouin echoes,” J. Lightwave Technol. 28(20), 2993–3003 (2010). [CrossRef]

] pump pulses, repeated measurements with pump pulses of different widths [21

21. W. Li, X. Bao, Y. Li, and L. Chen, “Differential pulse-width pair BOTDA for high spatial resolution sensing,” Opt. Express 16(26), 21616–21625 (2008). [CrossRef] [PubMed]

], differentiation of the signal power [22

22. T. Sperber, A. Eyal, M. Tur, and L. Thévenaz, “High spatial resolution distributed sensing in optical fibers by Brillouin gain-profile tracing,” Opt. Express 18(8), 8671–8679 (2010). [CrossRef] [PubMed]

] and many more. B-OTDA setups had reached spatial resolutions of 2 cm over 2 km of fiber [23

23. Y. Dong, H. Zhang, L. Chen, and X. Bao, “2 cm spatial-resolution and 2 km range Brillouin optical fiber sensor using a transient differential pulse pair,” Appl. Opt. 51(9), 1229–1235 (2012). [CrossRef] [PubMed]

].

PRBS phase modulation effectively decouples between range and resolution in B-OCDA. The method does suffer, however, from two primary drawbacks which are common to many B-OCDA implementations. First, although the off-peak acoustic field vanishes on average, its instantaneous value is nevertheless nonzero and fluctuating [24

24. Y. Antman, N. Levanon, and A. Zadok, “Low-noise delays from dynamic Brillouin gratings based on perfect Golomb coding of pump waves,” Opt. Lett. 37(24), 5259–5261 (2012). [CrossRef] [PubMed]

]. Residual off-peak reflectivity accumulates over the entire length of the fiber and severely degrades the signal-to-noise ratio (SNR) of the measurements. A large number of averages over repeated measurements are necessary to overcome this so-called 'coding noise' [24

24. Y. Antman, N. Levanon, and A. Zadok, “Low-noise delays from dynamic Brillouin gratings based on perfect Golomb coding of pump waves,” Opt. Lett. 37(24), 5259–5261 (2012). [CrossRef] [PubMed]

,31

31. Y. Antman, L. Yaron, T. Langer, M. Tur, N. Levanon, and A. Zadok, “Experimental demonstration of localized Brillouin gratings with low off-peak reflectivity established by perfect Golomb codes,” Opt. Lett. 38(22), 4701–4704 (2013). [CrossRef] [PubMed]

]. Second, the Brillouin gain spectrum must be mapped one spatial point at a time, scanning the entire length of the fiber in due course. The undertaking of tens of thousands of individual scans for every ν, using laboratory equipment, often proves impractical. For example, in [29

29. A. Zadok, Y. Antman, N. Primerov, A. Denisov, J. Sancho, and L. Thevenaz, “Random-access distributed fiber sensing,” Laser Photonics Rev. 6(5), L1–L5 (2012).

] we were able to scan an entire 40 m-long fiber with 1 cm resolution, but could not do the same for the entire 200 m-long fiber, due to excessive acquisition times.

An important step towards SNR improvement was made by Denisov et al. [32

32. A. Denisov, M. A. Soto, and L. Thévenaz, “Time gated phase-correlation distributed Brillouin fiber sensor,” Proc. SPIE 8794, 87943I (2013).

], who overlaid ns-scale amplitude pulse modulation on top of the PRBS phase coding of the pump wave. Using synchronized, time-gated measurements of the output signal, they were able to reduce the coding noise substantially and preform 1 cm-resolution measurements over a 3 km-long fiber. Their work can be regarded as a merger between B-OTDA and B-OCDA principles. Nevertheless, the issue of serial point-by-point acquisition still remained, and the complete mapping of the Brillouin gain spectrum over the entire set of 300,000 potential resolution points could not be performed.

In this work, we propose and demonstrate a combined B-OTDA / B-OCDA technique, which addresses both the measurement SNR and acquisition time. As in [32

32. A. Denisov, M. A. Soto, and L. Thévenaz, “Time gated phase-correlation distributed Brillouin fiber sensor,” Proc. SPIE 8794, 87943I (2013).

], an amplitude-pulsed pump and a CW signal are both phase modulated by a joint sequence, following the B-OCDA principle. However, two significant advances are introduced: First, a short, perfect Golomb code is used in the phase modulation of the pump and signal waves instead of a long PRBS. The special correlation properties of this sequence help reduce the coding noise considerably [24

24. Y. Antman, N. Levanon, and A. Zadok, “Low-noise delays from dynamic Brillouin gratings based on perfect Golomb coding of pump waves,” Opt. Lett. 37(24), 5259–5261 (2012). [CrossRef] [PubMed]

,31

31. Y. Antman, L. Yaron, T. Langer, M. Tur, N. Levanon, and A. Zadok, “Experimental demonstration of localized Brillouin gratings with low off-peak reflectivity established by perfect Golomb codes,” Opt. Lett. 38(22), 4701–4704 (2013). [CrossRef] [PubMed]

]. Second, due to the short length of the code, a large number of correlation peaks are generated during the propagation of the pump wave pulse. With careful choice of the pump pulse duration with respect to the Golomb code period and the Brillouin lifetime τ, the SBS amplification which takes place at the different peaks can be temporally resolved in measurements of the output signal power, much like in a B-OTDA. Using this method, the number of scans per choice of ν that is necessary for mapping the Brillouin gain spectrum over the entire fiber equals the length of the Golomb code only, which is 127 bits-long in our case. This number of scans is orders-of-magnitude smaller than that of an equivalent PRBS-coded B-OCDA, and it does not increase with the number of resolution points.

The experimental mapping of the Brillouin gain spectrum over a 400 m-long fiber with 2 cm resolution is reported below. The entire 20,000 resolution points are mapped by only 127 scans per choice of ν, representing a reduction of the acquisition time by a factor of about 150. A 5 cm-long hot spot is properly recognized and localized in the measurements. The technique might provide the breakthrough that is necessary to make high-resolution, long-range Brillouin-sensing more practical.

2. Principle of operation

The B-OTDA principle is known for many years, and has been explained at length in many references [3

3. T. Kurashima, T. Horiguchi, and M. Tateda, “Distributed-temperature sensing using stimulated Brillouin scattering in optical silica fibers,” Opt. Lett. 15(18), 1038–1040 (1990). [CrossRef] [PubMed]

]. The phase modulation-encoded B-OCDA concept was described in detail in our earlier works [29

29. A. Zadok, Y. Antman, N. Primerov, A. Denisov, J. Sancho, and L. Thevenaz, “Random-access distributed fiber sensing,” Laser Photonics Rev. 6(5), L1–L5 (2012).

,30

30. Y. Antman, N. Primerov, J. Sancho, L. Thevenaz, and A. Zadok, “Localized and stationary dynamic gratings via stimulated Brillouin scattering with phase modulated pumps,” Opt. Express 20(7), 7807–7821 (2012). [CrossRef] [PubMed]

]. The mathematical analyses of both will not be repeated here. We turn instead to the formulation of the SBS interaction between pump and signal waves that are modulated according to the combined technique which is the topic of the current work. We show later that the spatial-temporal profiles of both B-OTDA and phase-encoded B-OCDA can be obtained as specific cases of the analysis provided below.

Let us denote the optical fields of the pump and signal waves as Ep(t,z) and Es(t,z) respectively, were z denotes position along a fiber of length L and t represents time. The pump wave enters the fiber at z=0and propagates in the positive z direction, whereas the signal wave propagates from z=L in the negative z direction. We denote the complex envelopes of the pump and signal as Ap(t,z) and As(t,z) respectively, and their optical angular frequencies by ωp and ωs. The difference between the two frequencies: ωpωs=Ω=2πν is on the order of ΩB=2πνB.

In the proposed scheme, the signal envelope at its point of entry into the fiber is modulated by a phase sequence cn with a symbol duration T that is much shorter than the acoustic lifetime τ:

As(z=L,t)=As0ncnrect[tnTT]As(t)
(1)

Here As0 is a constant magnitude, cn is a prefect Golomb phase code of unity magnitude that is repeated every N symbols, and rect(ξ) equals 1 for |ξ|0.5 and zero elsewhere [24

24. Y. Antman, N. Levanon, and A. Zadok, “Low-noise delays from dynamic Brillouin gratings based on perfect Golomb coding of pump waves,” Opt. Lett. 37(24), 5259–5261 (2012). [CrossRef] [PubMed]

]. The pump wave envelope is also modulated by the same code, as in [24

24. Y. Antman, N. Levanon, and A. Zadok, “Low-noise delays from dynamic Brillouin gratings based on perfect Golomb coding of pump waves,” Opt. Lett. 37(24), 5259–5261 (2012). [CrossRef] [PubMed]

,29

29. A. Zadok, Y. Antman, N. Primerov, A. Denisov, J. Sancho, and L. Thevenaz, “Random-access distributed fiber sensing,” Laser Photonics Rev. 6(5), L1–L5 (2012).

31

31. Y. Antman, L. Yaron, T. Langer, M. Tur, N. Levanon, and A. Zadok, “Experimental demonstration of localized Brillouin gratings with low off-peak reflectivity established by perfect Golomb codes,” Opt. Lett. 38(22), 4701–4704 (2013). [CrossRef] [PubMed]

]. Unlike our earlier works, however, additional amplitude modulation by a single pulse is overlaid on top of the phase sequence:

Ap(z=0,t)=Ap0rect(tθ)ncnrect[tnTT]Ap(t)
(2)

In Eq. (2), Ap0is a constant magnitude and θ is the duration of the pump amplitude pulse. The phase sequence symbol duration T and the pulse duration θ are chosen so that θNT>τ.

The magnitude of the acoustic field at a given location is given by [30

30. Y. Antman, N. Primerov, J. Sancho, L. Thevenaz, and A. Zadok, “Localized and stationary dynamic gratings via stimulated Brillouin scattering with phase modulated pumps,” Opt. Express 20(7), 7807–7821 (2012). [CrossRef] [PubMed]

]:

Q(t,z)=jg10texp[ΓA(tt')]Ap(t'zvg)As*(t'zvgΔ(z))dt'
(3)

Here g1 is a parameter which depends on the electrostrictive coefficient, the speed of sound and the density of the fiber [1

1. R. W. Boyd, Nonlinear Optics, 3rd ed. (Academic, 2008).

], vg is the group velocity of light in the fiber, and the position-dependent temporal offset Δ(z) is defined as Δ(z)(2zL)/vg [30

30. Y. Antman, N. Primerov, J. Sancho, L. Thevenaz, and A. Zadok, “Localized and stationary dynamic gratings via stimulated Brillouin scattering with phase modulated pumps,” Opt. Express 20(7), 7807–7821 (2012). [CrossRef] [PubMed]

]. The spatial profile of the acoustic field is therefore closely associated with the cross-correlation between the two modulating envelopes. The exponential weighing bandwidth ΓA is determined by the choice of the optical frequencies offset ν: ΓA(Ω,z)j[(ΩB2(z)Ω2jΩΓB)/2Ω]. It reduces to half the Brillouin linewidth: ΓA=12ΓB=1/(2τ), when Ω=ΩB. Note that the Brillouin frequency shift might be position-dependent.

Fig. 3 Simulated magnitude of the acoustic wave density fluctuations (in normalized units), as a function of position and time along a 6 m-long fiber section. Panel(a): both pump and signal waves are co-modulated by a perfect Golomb phase code that is 127 bits long, with symbol duration of 200 ps. The simultaneous generation of multiple, periodic correlation peaks would lead to ambiguous measurement of the SBS amplification in monitoring the output signal power. Panel (b): The pump wave was modulated by a single amplitude pulse of 10 ns duration, whereas the signal wave was continuous (B-OTDA). Resolution limitations are illustrated.
For comparison, Fig. 3 shows the calculated |Q(z,t)| for the phase-coded B-OCDA scenario (θ,panel (a)), and for the B-OTDA case (cn=1 for all n, panel (b)). The SBS interaction in B-OTDA at any given instance spreads over a comparatively large spatial extent, restricting resolution. Use of short codes in B-OCDA, on the other hand, leads to ambiguous measurements of the output signal power due to the simultaneous generation of multiple peaks.

3. Experimental setup and results

Fig. 4 Experimental setup for combined B-OTDA / B-OCDA distributed sensing.
Figure 4 shows the experimental setup for high-resolution, extended-range Brillouin analysis using the proposed, combined B-OTDA / B-OCDA technique. Both pump and signal waves were drawn from a single laser diode source at 1550 nm wavelength. An electro-optic phase modulator at the laser output was driven by an arbitrary waveform generator (AWG). The AWG was programmed to repeatedly generate a 127 bits-long perfect Golomb code (see Appendix), with a symbol duration on the order of 200 ps. The output voltage of the generator was adjusted to match Vπ3.7V of the modulator.

Arbitrary locations along the fiber under test were addressed as follows [29

29. A. Zadok, Y. Antman, N. Primerov, A. Denisov, J. Sancho, and L. Thevenaz, “Random-access distributed fiber sensing,” Laser Photonics Rev. 6(5), L1–L5 (2012).

]: The joint phase modulation introduced multiple correlation peaks along the fiber ring that encompassed the pump branch, the signal branch, and fiber under test (see Fig. 4). The peaks were separated by NΔz=12NvgT2.6m. Hence the position of all peaks, except for the central one, varied with the symbol duration. The 4 km-long path imbalance along the signal branch guaranteed that off-centered correlation peaks were in overlap with the fiber under test. The position of these peaks could be scanned through slight changes to the Golomb code symbol duration: a 23.5 kbit/s variation in the nominal 5 Gbit/s phase modulation rate corresponded to an offset of the correlation peaks by Δz of 2 cm.

Fig. 6 Measured Brillouin gain map as a function of frequency offset between pump and signal, and position along a 400 m-long fiber under test. The fiber consisted of two sections, each approximately 200 m-long, with Brillouin shifts at room temperature of approximately 10.84 GHz and 10.90 GHz, respectively. A 5 cm-long hot spot was located towards the output end of the pump wave. The map was reconstructed using only 127 scans per frequency offset, according to the combined B-OTDA / B-OCDA method. The complete map is shown on panel (a), and a zoom-in on the hot spot region is shown on panel (b).
Figure 6 shows the SBS signal gain as a function of ν and z. The experimental procedure effectively reconstructed the Brillouin gain spectra at all 20,000 resolution points using only 127 scans for each choice of ν. The recovered values of νB(z) are shown in Fig. 7.
Fig. 7 Brillouin frequency shift as a function of position, as extracted from the experimental Brillouin gain map of Fig. 6 above.
The hot spot is well recognized (see inset).

4. Summary

In this work, we have proposed and demonstrated a combined B-OTDA / B-OCDA technique for distributed fiber-optic measurements of strain and temperature. Both SBS pump and signal are repeatedly co-modulated by a short and high-rate phase sequence, whose symbol duration is on the order of hundreds of ps and its period is somewhat longer than the Brillouin lifetime. In addition, the pump wave is also amplitude-modulated by a single pulse, whose duration equals the period of the phase sequence. The method provides the high resolution and long range of unambiguous measurements of phase-coded B-OCDA setups, with two significant improvements: a) Golomb phase codes are used instead of random sequences, and effectively reduce noise due to residual, off-peak Brillouin interactions; and b) The SBS amplification at a large number of correlation peaks is interrogated by the single pump pulse, and resolved in the time domain. The number of scans that is necessary to reconstruct the Brillouin gain for a specific frequency offset ν equals the length of the Golomb code. The number of scans is smaller than that of a corresponding phase-coded B-OCDA by over two orders of magnitude, and does not increase with the length of fiber under test.

The Brillouin gain spectrum was experimentally acquired over a 400 m-long fiber under test with 2 cm resolution. The entire set of 20,000 resolution points was mapped in only 127 scans per choice of frequency offset ν. A 5 cm-long hot spot, located towards the output end of the pump wave, was properly identified in the measurements. Each trace was averaged over 64 times. The overall acquisition time, for 40 values of ν, was about 1 second. The estimate does not include latencies due to data transfer by laboratory equipment and off-line signal processing, which would be performed in real-time by a realistic, dedicated instrument.

The uncertainty in the estimates of the local Brillouin shift was ± 3 MHz. These rather large variations can be reduced using a larger number of averages. The spatial resolution in the experiments was limited to 2 cm by the rate of waveform generators available to us. The technique is scalable to resolution below 1 cm [29

29. A. Zadok, Y. Antman, N. Primerov, A. Denisov, J. Sancho, and L. Thevenaz, “Random-access distributed fiber sensing,” Laser Photonics Rev. 6(5), L1–L5 (2012).

]. Higher resolution measurements would be associated with weaker SBS amplification, and stronger coding noise due to longer Golomb codes. Therefore, the necessary number of averages is expected to increase with resolution.

The technique represents a significant advance towards practical high-resolution, long-range Brillouin analysis. On-going work is dedicated to the reduction of the necessary number of averages, the extension of the measurement range beyond 1 km, and the employment of the technique in the monitoring of structures.

Appendix: Perfect Golomb code

The Golomb code used in the experiments and simulations is 127 bits long. All elements in the code are of unity magnitude. The phases of the following elements equal cos1(63/64): {1 2 4 8 9 11 13 15 16 17 18 19 21 22 25 26 30 31 32 34 35 36 37 38 41 42 44 47 49 50 52 60 61 62 64 68 69 70 71 72 73 74 76 79 81 82 84 87 88 94 98 99 100 103 104 107 113 115 117 120 121 122 124}. The phases of all other elements equal zero.

Acknowledgments

This work was supported in part by the Chief Scientist Office, the Israeli Ministry of Industry, Trade and Labor, through the KAMIN program.

References and links

1.

R. W. Boyd, Nonlinear Optics, 3rd ed. (Academic, 2008).

2.

A. Zadok, A. Eyal, and M. Tur, “Stimulated Brillouin scattering slow light in optical fibers [Invited],” Appl. Opt. 50(25), E38–E49 (2011). [CrossRef]

3.

T. Kurashima, T. Horiguchi, and M. Tateda, “Distributed-temperature sensing using stimulated Brillouin scattering in optical silica fibers,” Opt. Lett. 15(18), 1038–1040 (1990). [CrossRef] [PubMed]

4.

T. Horiguchi, T. Kurashima, and M. Tateda, “A technique to measure distributed strain in optical fibers,” IEEE Photonics Technol. Lett. 2(5), 352–354 (1990). [CrossRef]

5.

M. Niklès, L. Thévenaz, and P. A. Robert, “Simple distributed fiber sensor based on Brillouin gain spectrum analysis,” Opt. Lett. 21(10), 758–760 (1996). [CrossRef] [PubMed]

6.

X. Bao and L. A. Chen, “Recent progress in Brillouin scattering based fiber sensors,” Sensors (Basel) 11(4), 4152–4187 (2011). [CrossRef] [PubMed]

7.

S. Martin-Lopez, M. Alcon-Camas, F. Rodriguez, P. Corredera, J. D. Ania-Castañon, L. Thévenaz, and M. Gonzalez-Herraez, “Brillouin optical time-domain analysis assisted by second-order Raman amplification,” Opt. Express 18(18), 18769–18778 (2010). [CrossRef] [PubMed]

8.

M. A. Soto, G. Bolognini, and F. Di Pasquale, “Long-range simplex-coded BOTDA sensor over 120 km distance employing optical preamplification,” Opt. Lett. 36(2), 232–234 (2011). [CrossRef] [PubMed]

9.

M. A. Soto, G. Bolognini, and F. Di Pasquale, “Optimization of long-range BOTDA sensors with high resolution using first-order bi-directional Raman amplification,” Opt. Express 19(5), 4444–4457 (2011). [CrossRef] [PubMed]

10.

Y. Dong, L. Chen, and X. Bao, “Time-division multiplexing-based BOTDA over 100 km sensing length,” Opt. Lett. 36(2), 277–279 (2011). [CrossRef] [PubMed]

11.

Y. Peled, A. Motil, L. Yaron, and M. Tur, “Slope-assisted fast distributed sensing in optical fibers with arbitrary Brillouin profile,” Opt. Express 19(21), 19845–19854 (2011). [CrossRef] [PubMed]

12.

Y. Peled, A. Motil, and M. Tur, “Fast Brillouin optical time domain analysis for dynamic sensing,” Opt. Express 20(8), 8584–8591 (2012). [CrossRef] [PubMed]

13.

Y. Peled, A. Motil, I. Kressel, and M. Tur, “Monitoring the propagation of mechanical waves using an optical fiber distributed and dynamic strain sensor based on BOTDA,” Opt. Express 21(9), 10697–10705 (2013). [CrossRef] [PubMed]

14.

A. Fellay, L. Thevenaz, M. Facchini, M. Nikles, and P. Robert, “Distributed sensing using stimulated Brillouin scattering: towards ultimate resolution,” in 12th International Conference on Optical Fiber Sensors, Vol. 16 of 1997 OSA Technical Digest Series (Optical Society of America, 1997), paper OWD3.

15.

J. C. Beugnot, M. Tur, S. F. Mafang, and L. Thévenaz, “Distributed Brillouin sensing with sub-meter spatial resolution: modeling and processing,” Opt. Express 19(8), 7381–7397 (2011). [CrossRef] [PubMed]

16.

V. Lecoeuche, D. J. Webb, C. N. Pannell, and D. A. Jackson, “Transient response in high-resolution Brillouin-based distributed sensing using probe pulses shorter than the acoustic relaxation time,” Opt. Lett. 25(3), 156–158 (2000). [CrossRef] [PubMed]

17.

F. Wang, X. Bao, L. Chen, Y. Li, J. Snoddy, and X. Zhang, “Using pulse with a dark base to achieve high spatial and frequency resolution for the distributed Brillouin sensor,” Opt. Lett. 33(22), 2707–2709 (2008). [CrossRef] [PubMed]

18.

A. W. Brown, B. G. Colpitts, and K. Brown, “Distributed sensor based on dark-pulse Brillouin scattering,” IEEE Photonics Technol. Lett. 17(7), 1501–1503 (2005). [CrossRef]

19.

L. Thévenaz and S. F. Mafang, “Distributed fiber sensing using Brillouin echoes,” Proc. SPIE 7004, 70043N (2008).

20.

S. Foaleng Mafang, M. Tur, J. C. Beugnot, and L. Thevenaz, “High spatial and spectral resolution long-range sensing using Brillouin echoes,” J. Lightwave Technol. 28(20), 2993–3003 (2010). [CrossRef]

21.

W. Li, X. Bao, Y. Li, and L. Chen, “Differential pulse-width pair BOTDA for high spatial resolution sensing,” Opt. Express 16(26), 21616–21625 (2008). [CrossRef] [PubMed]

22.

T. Sperber, A. Eyal, M. Tur, and L. Thévenaz, “High spatial resolution distributed sensing in optical fibers by Brillouin gain-profile tracing,” Opt. Express 18(8), 8671–8679 (2010). [CrossRef] [PubMed]

23.

Y. Dong, H. Zhang, L. Chen, and X. Bao, “2 cm spatial-resolution and 2 km range Brillouin optical fiber sensor using a transient differential pulse pair,” Appl. Opt. 51(9), 1229–1235 (2012). [CrossRef] [PubMed]

24.

Y. Antman, N. Levanon, and A. Zadok, “Low-noise delays from dynamic Brillouin gratings based on perfect Golomb coding of pump waves,” Opt. Lett. 37(24), 5259–5261 (2012). [CrossRef] [PubMed]

25.

K. Hotate and T. Hasegawa, “Measurement of Brillouin gain spectrum distribution along an optical fiber using a correlation-based technique-proposal, experiment and simulation,” IEICE Trans. Electron. E83-C(3), 405–412 (2000).

26.

K. Y. Song, Z. He, and K. Hotate, “Distributed strain measurement with millimeter-order spatial resolution based on Brillouin optical correlation domain analysis,” Opt. Lett. 31(17), 2526–2528 (2006). [CrossRef] [PubMed]

27.

W. Zou, Z. He, and K. Hotate, “Range elongation of distributed discrimination of strain and temperature in Brillouin optical correlation-domain analysis based on dual frequency modulations,” IEEE Sens. J. 14(1), 244–248 (2014). [CrossRef]

28.

J. H. Jeong, K. Lee, K. Y. Song, J. M. Jeong, and S. B. Lee, “Differential measurement scheme for Brillouin Optical Correlation Domain Analysis,” Opt. Express 20(24), 27094–27101 (2012). [CrossRef] [PubMed]

29.

A. Zadok, Y. Antman, N. Primerov, A. Denisov, J. Sancho, and L. Thevenaz, “Random-access distributed fiber sensing,” Laser Photonics Rev. 6(5), L1–L5 (2012).

30.

Y. Antman, N. Primerov, J. Sancho, L. Thevenaz, and A. Zadok, “Localized and stationary dynamic gratings via stimulated Brillouin scattering with phase modulated pumps,” Opt. Express 20(7), 7807–7821 (2012). [CrossRef] [PubMed]

31.

Y. Antman, L. Yaron, T. Langer, M. Tur, N. Levanon, and A. Zadok, “Experimental demonstration of localized Brillouin gratings with low off-peak reflectivity established by perfect Golomb codes,” Opt. Lett. 38(22), 4701–4704 (2013). [CrossRef] [PubMed]

32.

A. Denisov, M. A. Soto, and L. Thévenaz, “Time gated phase-correlation distributed Brillouin fiber sensor,” Proc. SPIE 8794, 87943I (2013).

33.

A. Zadok, E. Zilka, A. Eyal, L. Thévenaz, and M. Tur, “Vector analysis of stimulated Brillouin scattering amplification in standard single-mode fibers,” Opt. Express 16(26), 21692–21707 (2008). [CrossRef] [PubMed]

OCIS Codes
(060.2370) Fiber optics and optical communications : Fiber optics sensors
(190.4370) Nonlinear optics : Nonlinear optics, fibers
(290.5900) Scattering : Scattering, stimulated Brillouin
(190.2055) Nonlinear optics : Dynamic gratings

ToC Category:
Sensors

History
Original Manuscript: November 28, 2013
Revised Manuscript: February 10, 2014
Manuscript Accepted: February 14, 2014
Published: March 12, 2014

Citation
David Elooz, Yair Antman, Nadav Levanon, and Avi Zadok, "High-resolution long-reach distributed Brillouin sensing based on combined time-domain and correlation-domain analysis," Opt. Express 22, 6453-6463 (2014)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-22-6-6453


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References

  1. R. W. Boyd, Nonlinear Optics, 3rd ed. (Academic, 2008).
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  8. M. A. Soto, G. Bolognini, F. Di Pasquale, “Long-range simplex-coded BOTDA sensor over 120 km distance employing optical preamplification,” Opt. Lett. 36(2), 232–234 (2011). [CrossRef] [PubMed]
  9. M. A. Soto, G. Bolognini, F. Di Pasquale, “Optimization of long-range BOTDA sensors with high resolution using first-order bi-directional Raman amplification,” Opt. Express 19(5), 4444–4457 (2011). [CrossRef] [PubMed]
  10. Y. Dong, L. Chen, X. Bao, “Time-division multiplexing-based BOTDA over 100 km sensing length,” Opt. Lett. 36(2), 277–279 (2011). [CrossRef] [PubMed]
  11. Y. Peled, A. Motil, L. Yaron, M. Tur, “Slope-assisted fast distributed sensing in optical fibers with arbitrary Brillouin profile,” Opt. Express 19(21), 19845–19854 (2011). [CrossRef] [PubMed]
  12. Y. Peled, A. Motil, M. Tur, “Fast Brillouin optical time domain analysis for dynamic sensing,” Opt. Express 20(8), 8584–8591 (2012). [CrossRef] [PubMed]
  13. Y. Peled, A. Motil, I. Kressel, M. Tur, “Monitoring the propagation of mechanical waves using an optical fiber distributed and dynamic strain sensor based on BOTDA,” Opt. Express 21(9), 10697–10705 (2013). [CrossRef] [PubMed]
  14. A. Fellay, L. Thevenaz, M. Facchini, M. Nikles, and P. Robert, “Distributed sensing using stimulated Brillouin scattering: towards ultimate resolution,” in 12th International Conference on Optical Fiber Sensors, Vol. 16 of 1997 OSA Technical Digest Series (Optical Society of America, 1997), paper OWD3.
  15. J. C. Beugnot, M. Tur, S. F. Mafang, L. Thévenaz, “Distributed Brillouin sensing with sub-meter spatial resolution: modeling and processing,” Opt. Express 19(8), 7381–7397 (2011). [CrossRef] [PubMed]
  16. V. Lecoeuche, D. J. Webb, C. N. Pannell, D. A. Jackson, “Transient response in high-resolution Brillouin-based distributed sensing using probe pulses shorter than the acoustic relaxation time,” Opt. Lett. 25(3), 156–158 (2000). [CrossRef] [PubMed]
  17. F. Wang, X. Bao, L. Chen, Y. Li, J. Snoddy, X. Zhang, “Using pulse with a dark base to achieve high spatial and frequency resolution for the distributed Brillouin sensor,” Opt. Lett. 33(22), 2707–2709 (2008). [CrossRef] [PubMed]
  18. A. W. Brown, B. G. Colpitts, K. Brown, “Distributed sensor based on dark-pulse Brillouin scattering,” IEEE Photonics Technol. Lett. 17(7), 1501–1503 (2005). [CrossRef]
  19. L. Thévenaz, S. F. Mafang, “Distributed fiber sensing using Brillouin echoes,” Proc. SPIE 7004, 70043N (2008).
  20. S. Foaleng Mafang, M. Tur, J. C. Beugnot, L. Thevenaz, “High spatial and spectral resolution long-range sensing using Brillouin echoes,” J. Lightwave Technol. 28(20), 2993–3003 (2010). [CrossRef]
  21. W. Li, X. Bao, Y. Li, L. Chen, “Differential pulse-width pair BOTDA for high spatial resolution sensing,” Opt. Express 16(26), 21616–21625 (2008). [CrossRef] [PubMed]
  22. T. Sperber, A. Eyal, M. Tur, L. Thévenaz, “High spatial resolution distributed sensing in optical fibers by Brillouin gain-profile tracing,” Opt. Express 18(8), 8671–8679 (2010). [CrossRef] [PubMed]
  23. Y. Dong, H. Zhang, L. Chen, X. Bao, “2 cm spatial-resolution and 2 km range Brillouin optical fiber sensor using a transient differential pulse pair,” Appl. Opt. 51(9), 1229–1235 (2012). [CrossRef] [PubMed]
  24. Y. Antman, N. Levanon, A. Zadok, “Low-noise delays from dynamic Brillouin gratings based on perfect Golomb coding of pump waves,” Opt. Lett. 37(24), 5259–5261 (2012). [CrossRef] [PubMed]
  25. K. Hotate, T. Hasegawa, “Measurement of Brillouin gain spectrum distribution along an optical fiber using a correlation-based technique-proposal, experiment and simulation,” IEICE Trans. Electron. E83-C(3), 405–412 (2000).
  26. K. Y. Song, Z. He, K. Hotate, “Distributed strain measurement with millimeter-order spatial resolution based on Brillouin optical correlation domain analysis,” Opt. Lett. 31(17), 2526–2528 (2006). [CrossRef] [PubMed]
  27. W. Zou, Z. He, K. Hotate, “Range elongation of distributed discrimination of strain and temperature in Brillouin optical correlation-domain analysis based on dual frequency modulations,” IEEE Sens. J. 14(1), 244–248 (2014). [CrossRef]
  28. J. H. Jeong, K. Lee, K. Y. Song, J. M. Jeong, S. B. Lee, “Differential measurement scheme for Brillouin Optical Correlation Domain Analysis,” Opt. Express 20(24), 27094–27101 (2012). [CrossRef] [PubMed]
  29. A. Zadok, Y. Antman, N. Primerov, A. Denisov, J. Sancho, L. Thevenaz, “Random-access distributed fiber sensing,” Laser Photonics Rev. 6(5), L1–L5 (2012).
  30. Y. Antman, N. Primerov, J. Sancho, L. Thevenaz, A. Zadok, “Localized and stationary dynamic gratings via stimulated Brillouin scattering with phase modulated pumps,” Opt. Express 20(7), 7807–7821 (2012). [CrossRef] [PubMed]
  31. Y. Antman, L. Yaron, T. Langer, M. Tur, N. Levanon, A. Zadok, “Experimental demonstration of localized Brillouin gratings with low off-peak reflectivity established by perfect Golomb codes,” Opt. Lett. 38(22), 4701–4704 (2013). [CrossRef] [PubMed]
  32. A. Denisov, M. A. Soto, L. Thévenaz, “Time gated phase-correlation distributed Brillouin fiber sensor,” Proc. SPIE 8794, 87943I (2013).
  33. A. Zadok, E. Zilka, A. Eyal, L. Thévenaz, M. Tur, “Vector analysis of stimulated Brillouin scattering amplification in standard single-mode fibers,” Opt. Express 16(26), 21692–21707 (2008). [CrossRef] [PubMed]

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