Abstract

A theoretical and experimental analysis of the impact of pulse modulation format on Brillouin optical time-domain analysis (BOTDA) sensors using pulse coding techniques has been carried out. Pulse coding with conventional non-return-to-zero (NRZ) modulation format is shown to induce significant distortions in the measured Brillouin gain spectrum (BGS), especially in proximity of abrupt changes in the fiber gain spectra. Such an effect, as confirmed by the theoretical analysis, is due to acoustic wave pre-excitation and non-uniform gain which depends on the bit patterns defined by the different codewords. A successful use of pulse coding techniques then requires to suitably optimize the employed modulation format in order to avoid spurious oscillations causing severe penalties in the attained accuracy. Coding technique with return-to-zero (RZ) modulation format is analyzed under different duty-cycle conditions for a 25 km-long sensing scheme, showing that low duty-cycle values are able to effectively suppress the induced distortions in the BGS and allow for spatially-accurate, high-resolution strain and temperature measurements being able to fully exploit the provided coding gain (~7.2 dB along 25 km distance) with unaltered spatial resolution (1 meter). Although Simplex coding is used in our analysis, the validity of the results is general and can be directly applied to any intensity-modulation coding scheme.

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  1. A. Minardo, R. Bernini, L. Zeni, L. Thévenaz, and F. Briffod, “A reconstruction technique for long-range stimulated Brillouin scattering distributed fibre-optic sensors: experimental results,” Meas. Sci. Technol. 16(4), 900–908 (2005).
    [CrossRef]
  2. S. Diaz, S. F. Mafang, M. Lopez-Amo, and L. Thévenaz, “A High-performance Optical Time-Domain Brillouin Distributed Fiber Sensor,” IEEE Sens. J. 8(7), 1268–1272 (2008).
    [CrossRef]
  3. L. Thévenaz, and S. F. Mafang, “Distributed fiber sensing using Brillouin echoes,” Proc. SPIE 7004, 19th International Conference on Optical Fibre Sensors (OFS19), 2008, paper 3N.
  4. Y. Dong, X. Bao, and W. Li, “12-km distributed fiber sensor based on differential pulse-width pair BOTDA,” Proc. SPIE vol. 7503, 20th International Conference on Optical Fiber Sensors (OFS20), 2009, paper 2G.
  5. M. D. Jones, “Using Simplex codes to improve OTDR Sensitivity,” IEEE Photon. Technol. Lett. 15(7), 822–824 (1993).
    [CrossRef]
  6. M. A. Soto, G. Bolognini, F. Di Pasquale, and L. Thévenaz, “Simplex-coded BOTDA fiber sensor with 1 m spatial resolution over a 50 km range,” Opt. Lett. 35(2), 259–261 (2010).
    [CrossRef] [PubMed]
  7. N. Linze, W. Li, and X. Bao, “Signal-to-noise ratio improvement in Brillouin sensing,” Proc. of SPIE vol. 7503, 20th International Conference on Optical Fiber Sensors (OFS20), 2009, paper 6F.
  8. T. Horiguchi, K. Shimizu, T. Kurashima, M. Tateda, and Y. Koyamada, “Development of a Distributed Sensing Technique Using Brillouin Scattering,” J. Lightwave Technol. 13(7), 1296–1302 (1995).
    [CrossRef]
  9. D. Alasia, M. González Herráez, L. Abrardi, S. Martin-López, and L. Thévenaz, “Detrimental effect of modulation instability on distributed optical fiber sensors using stimulated Brillouin scattering,” Proc. SPIE 5855, 17th International Conference on Optical Fibre Sensors (OFS17), 2005, pp. 587–590.
  10. X. Bao, A. Brown, M. Demerchant, and J. Smith, “Characterization of the Brillouin-loss spectrum of single-mode fibers by use of very short (<10-ns) pulses,” Opt. Lett. 24(8), 510–512 (1999).
    [CrossRef]
  11. L. Thévenaz, and J.-C. Beugnot, “General analytical model for distributed Brillouin sensors with sub-meter spatial resolution” in 20th International Conference on Optical Fiber Sensors (OFS20), 2009, paper 6A.

2010 (1)

2008 (1)

S. Diaz, S. F. Mafang, M. Lopez-Amo, and L. Thévenaz, “A High-performance Optical Time-Domain Brillouin Distributed Fiber Sensor,” IEEE Sens. J. 8(7), 1268–1272 (2008).
[CrossRef]

2005 (1)

A. Minardo, R. Bernini, L. Zeni, L. Thévenaz, and F. Briffod, “A reconstruction technique for long-range stimulated Brillouin scattering distributed fibre-optic sensors: experimental results,” Meas. Sci. Technol. 16(4), 900–908 (2005).
[CrossRef]

1999 (1)

1995 (1)

T. Horiguchi, K. Shimizu, T. Kurashima, M. Tateda, and Y. Koyamada, “Development of a Distributed Sensing Technique Using Brillouin Scattering,” J. Lightwave Technol. 13(7), 1296–1302 (1995).
[CrossRef]

1993 (1)

M. D. Jones, “Using Simplex codes to improve OTDR Sensitivity,” IEEE Photon. Technol. Lett. 15(7), 822–824 (1993).
[CrossRef]

Bao, X.

Bernini, R.

A. Minardo, R. Bernini, L. Zeni, L. Thévenaz, and F. Briffod, “A reconstruction technique for long-range stimulated Brillouin scattering distributed fibre-optic sensors: experimental results,” Meas. Sci. Technol. 16(4), 900–908 (2005).
[CrossRef]

Bolognini, G.

Briffod, F.

A. Minardo, R. Bernini, L. Zeni, L. Thévenaz, and F. Briffod, “A reconstruction technique for long-range stimulated Brillouin scattering distributed fibre-optic sensors: experimental results,” Meas. Sci. Technol. 16(4), 900–908 (2005).
[CrossRef]

Brown, A.

Demerchant, M.

Di Pasquale, F.

Diaz, S.

S. Diaz, S. F. Mafang, M. Lopez-Amo, and L. Thévenaz, “A High-performance Optical Time-Domain Brillouin Distributed Fiber Sensor,” IEEE Sens. J. 8(7), 1268–1272 (2008).
[CrossRef]

Horiguchi, T.

T. Horiguchi, K. Shimizu, T. Kurashima, M. Tateda, and Y. Koyamada, “Development of a Distributed Sensing Technique Using Brillouin Scattering,” J. Lightwave Technol. 13(7), 1296–1302 (1995).
[CrossRef]

Jones, M. D.

M. D. Jones, “Using Simplex codes to improve OTDR Sensitivity,” IEEE Photon. Technol. Lett. 15(7), 822–824 (1993).
[CrossRef]

Koyamada, Y.

T. Horiguchi, K. Shimizu, T. Kurashima, M. Tateda, and Y. Koyamada, “Development of a Distributed Sensing Technique Using Brillouin Scattering,” J. Lightwave Technol. 13(7), 1296–1302 (1995).
[CrossRef]

Kurashima, T.

T. Horiguchi, K. Shimizu, T. Kurashima, M. Tateda, and Y. Koyamada, “Development of a Distributed Sensing Technique Using Brillouin Scattering,” J. Lightwave Technol. 13(7), 1296–1302 (1995).
[CrossRef]

Lopez-Amo, M.

S. Diaz, S. F. Mafang, M. Lopez-Amo, and L. Thévenaz, “A High-performance Optical Time-Domain Brillouin Distributed Fiber Sensor,” IEEE Sens. J. 8(7), 1268–1272 (2008).
[CrossRef]

Mafang, S. F.

S. Diaz, S. F. Mafang, M. Lopez-Amo, and L. Thévenaz, “A High-performance Optical Time-Domain Brillouin Distributed Fiber Sensor,” IEEE Sens. J. 8(7), 1268–1272 (2008).
[CrossRef]

Minardo, A.

A. Minardo, R. Bernini, L. Zeni, L. Thévenaz, and F. Briffod, “A reconstruction technique for long-range stimulated Brillouin scattering distributed fibre-optic sensors: experimental results,” Meas. Sci. Technol. 16(4), 900–908 (2005).
[CrossRef]

Shimizu, K.

T. Horiguchi, K. Shimizu, T. Kurashima, M. Tateda, and Y. Koyamada, “Development of a Distributed Sensing Technique Using Brillouin Scattering,” J. Lightwave Technol. 13(7), 1296–1302 (1995).
[CrossRef]

Smith, J.

Soto, M. A.

Tateda, M.

T. Horiguchi, K. Shimizu, T. Kurashima, M. Tateda, and Y. Koyamada, “Development of a Distributed Sensing Technique Using Brillouin Scattering,” J. Lightwave Technol. 13(7), 1296–1302 (1995).
[CrossRef]

Thévenaz, L.

M. A. Soto, G. Bolognini, F. Di Pasquale, and L. Thévenaz, “Simplex-coded BOTDA fiber sensor with 1 m spatial resolution over a 50 km range,” Opt. Lett. 35(2), 259–261 (2010).
[CrossRef] [PubMed]

S. Diaz, S. F. Mafang, M. Lopez-Amo, and L. Thévenaz, “A High-performance Optical Time-Domain Brillouin Distributed Fiber Sensor,” IEEE Sens. J. 8(7), 1268–1272 (2008).
[CrossRef]

A. Minardo, R. Bernini, L. Zeni, L. Thévenaz, and F. Briffod, “A reconstruction technique for long-range stimulated Brillouin scattering distributed fibre-optic sensors: experimental results,” Meas. Sci. Technol. 16(4), 900–908 (2005).
[CrossRef]

Zeni, L.

A. Minardo, R. Bernini, L. Zeni, L. Thévenaz, and F. Briffod, “A reconstruction technique for long-range stimulated Brillouin scattering distributed fibre-optic sensors: experimental results,” Meas. Sci. Technol. 16(4), 900–908 (2005).
[CrossRef]

IEEE Photon. Technol. Lett. (1)

M. D. Jones, “Using Simplex codes to improve OTDR Sensitivity,” IEEE Photon. Technol. Lett. 15(7), 822–824 (1993).
[CrossRef]

IEEE Sens. J. (1)

S. Diaz, S. F. Mafang, M. Lopez-Amo, and L. Thévenaz, “A High-performance Optical Time-Domain Brillouin Distributed Fiber Sensor,” IEEE Sens. J. 8(7), 1268–1272 (2008).
[CrossRef]

J. Lightwave Technol. (1)

T. Horiguchi, K. Shimizu, T. Kurashima, M. Tateda, and Y. Koyamada, “Development of a Distributed Sensing Technique Using Brillouin Scattering,” J. Lightwave Technol. 13(7), 1296–1302 (1995).
[CrossRef]

Meas. Sci. Technol. (1)

A. Minardo, R. Bernini, L. Zeni, L. Thévenaz, and F. Briffod, “A reconstruction technique for long-range stimulated Brillouin scattering distributed fibre-optic sensors: experimental results,” Meas. Sci. Technol. 16(4), 900–908 (2005).
[CrossRef]

Opt. Lett. (2)

Other (5)

D. Alasia, M. González Herráez, L. Abrardi, S. Martin-López, and L. Thévenaz, “Detrimental effect of modulation instability on distributed optical fiber sensors using stimulated Brillouin scattering,” Proc. SPIE 5855, 17th International Conference on Optical Fibre Sensors (OFS17), 2005, pp. 587–590.

L. Thévenaz, and J.-C. Beugnot, “General analytical model for distributed Brillouin sensors with sub-meter spatial resolution” in 20th International Conference on Optical Fiber Sensors (OFS20), 2009, paper 6A.

L. Thévenaz, and S. F. Mafang, “Distributed fiber sensing using Brillouin echoes,” Proc. SPIE 7004, 19th International Conference on Optical Fibre Sensors (OFS19), 2008, paper 3N.

Y. Dong, X. Bao, and W. Li, “12-km distributed fiber sensor based on differential pulse-width pair BOTDA,” Proc. SPIE vol. 7503, 20th International Conference on Optical Fiber Sensors (OFS20), 2009, paper 2G.

N. Linze, W. Li, and X. Bao, “Signal-to-noise ratio improvement in Brillouin sensing,” Proc. of SPIE vol. 7503, 20th International Conference on Optical Fiber Sensors (OFS20), 2009, paper 6F.

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Figures (18)

Fig. 1
Fig. 1

Transient behavior of conventional Simplex-coded BOTDA sensors. (a) Normalized acoustic-wave amplitude. (b) Normalized Brillouin gain.

Fig. 2
Fig. 2

Normalized acoustic-wave intensity using return-to-zero pulse modulation format.

Fig. 3
Fig. 3

Experimental setup.

Fig. 4
Fig. 4

Coded-BOTDA traces measured with 127-bit Simplex coding based on NRZ pulses.

Fig. 5
Fig. 5

(a) Simplex-coded sequence based on NRZ pulses, and corresponding (b) normalized acoustic-wave intensity and (c) normalized Brillouin gain.

Fig. 6
Fig. 6

Coded-BOTDA traces near the temperature transitions, at different frequencies.

Fig. 7
Fig. 7

Decoded BGS as a function of the distance, near the temperature transitions, when using 127-bit Simplex coding with NRZ pulses.

Fig. 8
Fig. 8

Measured (decoded) and fitted BGS at a distance of (a) 11 km, (b) ~11.6 km, and (c) ~12.6 km, when using Simplex coding with NRZ pulses.

Fig. 9
Fig. 9

(a) Measured BGS vs distance. (b) Measured and fitted BGS at ~11.6-km distance.

Fig. 10
Fig. 10

Simplex coding based on RZ pulses.

Fig. 11
Fig. 11

Normalized intensity for coded-BOTDA traces obtained with codewords #1 and #64. (a) Using NRZ pulses. (b) Using RZ pulses with 25% duty-cycle. (c) Using RZ pulses with 16.7% duty-cycle.

Fig. 12
Fig. 12

Relative intensity difference as a function of the bit slot.

Fig. 13
Fig. 13

Coded-BOTDA traces measured with 127-bit Simplex coding base on RZ pulses with 16.7% duty cycle.

Fig. 14
Fig. 14

(a) Simplex-coded sequence based on RZ pulses with 16.7% duty cycle, and corresponding (b) normalized acoustic-wave intensity and (c) normalized Brillouin gain.

Fig. 15
Fig. 15

Decoded BGS as a function of the distance, near the temperature transitions, when using 127-bit Simplex coding with RZ pulses (16.7% duty cycle).

Fig. 16
Fig. 16

Measurement and fitting of BGS at a distance of (a) 11 km, (b) ~11.6 km, and (c) ~12.6 km, when using Simplex coding with RZ pulses (16.7% duty cycle).

Fig. 17
Fig. 17

BOTDA traces at ~10.556 GHz (peak frequency of the third fiber spool) obtained with both 127-bit simplex coding, using RZ pulses with 16.7% duty cycle, and conventional single-pulsed BOTDA

Fig. 18
Fig. 18

BFS around temperature transitions using 127-bit Simplex coding with RZ pulses. Inset, achieved temperature resolution.

Equations (8)

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Δ B F S ( z ) = C ν B ε Δ ε ( z ) + C ν B T Δ T ( z ) ,
Δ I C W ( t , Δ ν ) = I C W L exp ( α L ) { G ( t , Δ ν ) 1 } ,
G ( t , Δ ν ) = exp [ v g t / 2 v g t / 2 + Δ z g B ( ξ , Δ ν ) I p ( ξ , Δ ν ) d ξ ] ,
f p V ( Δ ν ) = G max { c Δ ν B 2 Δ ν B 2 + 4 ( Δ ν ν B ) 2 + ( 1 c ) exp [ 4 ln 2 ( Δ ν ν B ) 2 Δ ν B 2 ] } ,
δ ν B = Δ ν B 2 ( S N R ) 1 / 4 ,
Δ I C W ( t , Δ ν ) v g t / 2 v g t / 2 + Δ z g B ( ξ , Δ ν ) I p ( ξ , Δ ν ) d ξ .
( z + 1 v g t ) E P = i 1 2 g 2 Q E S , ( z + 1 v g t ) E S = i 1 2 g 2 Q * E P , ( t + Γ A ) Q = i g 1 E P E S * ,
Difference ( % ) = Max( Coded   trace   64 ) Max( Coded   trace   1 ) Max( Coded   trace   64 ) x 100.

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