Abstract

An offset locking technique, which uses an external optical delay line to tune the distributed feedback (DFB) laser frequency and a proportional-integral-derivative (PID) controller to lock the tuned frequency, is proposed for the first time, to the best of our knowledge, in the distributed Brillouin sensor system. This method provides large tuning range (greater than 1  GHz), high tuning speed (less than 100μs per frequency step), and frequency tuning is independent of the laser frequency and power. The two DFB lasers are phase locked at the Brillouin frequency using a hardware PID controller. Using this offset locking with optical delay line, we demonstrated a high signal-to-noise ratio of 32  dB, which allows 1  m spatial resolution and better than 0.6  MHz frequency measurement accuracy (equivalent to 0.5°C temperature resolution or 8με strain resolution) over kilometers sensing length. The bias of the electro-optic modulator is controlled by a lock-in amplifier to provide high temperature or strain measurement accuracy.

© 2008 Optical Society of America

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References

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    [CrossRef]
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    [CrossRef]

2006

F. Ravet, X. Bao, L. Zou, Q. Yu, Y. Li, V. Kalosha, and L. Chen, "Accurate strain detection and localization with distributed Brillouin sensor based on a phenomenological signal processing approach," Proc. SPIE 6176, 61761C (2006).
[CrossRef]

X. Bao, Q. Yu, V. P. Kalosha, and L. Chen, "The influence of prolonged phonon relaxation on the Brillouin loss spectrum for the nanosecond pulses," Opt. Lett. 31, 888-890 (2006).
[CrossRef] [PubMed]

2005

2004

L. Thevenaz, S. Le Floch, D. Alasia, and J. Troger, "Novel schemes for optical signal generation using laser injection locking with application to Brillouin sensing," Meas. Sci. Technol. 15, 1519-1524 (2004).
[CrossRef]

2001

Y. Doi, S. Fukushima, T. Ohno, and K. Yoshino, "Frequency stabilization of millimeter-wave sub carrier using laser heterodyne source and optical delay line," IEEE Photon. Technol. Lett. 13, 1002-1004 (2001).
[CrossRef]

1999

A. W. Brown, J. P. Smith, and X. Bao, "Brillouin scattering based distributed sensors for structural applications," J. Intell. Mater. Syst. Struct. 10, 340-349 (1999).
[CrossRef]

1996

H. Izumita, T. Sato, M. Tateda, and Y. Koyamada, "Brillouin OTDR employing optical frequency shifter using side-band generation technique with high-speed LN phase-modulator," IEEE Photon. Technol. Lett. 8, 1674-1676 (1996).
[CrossRef]

M. Nikles, L. Thevenaz, and P. A. Robert, "Simple distributed fiber sensor based on Brillouin gain spectrum analysis," Opt. Lett. 21, 758-760 (1996).
[CrossRef] [PubMed]

1993

1990

IEEE Photon. Technol. Lett.

H. Izumita, T. Sato, M. Tateda, and Y. Koyamada, "Brillouin OTDR employing optical frequency shifter using side-band generation technique with high-speed LN phase-modulator," IEEE Photon. Technol. Lett. 8, 1674-1676 (1996).
[CrossRef]

Y. Doi, S. Fukushima, T. Ohno, and K. Yoshino, "Frequency stabilization of millimeter-wave sub carrier using laser heterodyne source and optical delay line," IEEE Photon. Technol. Lett. 13, 1002-1004 (2001).
[CrossRef]

J. Intell. Mater. Syst. Struct.

A. W. Brown, J. P. Smith, and X. Bao, "Brillouin scattering based distributed sensors for structural applications," J. Intell. Mater. Syst. Struct. 10, 340-349 (1999).
[CrossRef]

Meas. Sci. Technol.

L. Thevenaz, S. Le Floch, D. Alasia, and J. Troger, "Novel schemes for optical signal generation using laser injection locking with application to Brillouin sensing," Meas. Sci. Technol. 15, 1519-1524 (2004).
[CrossRef]

Opt. Lett.

Proc. SPIE

F. Ravet, X. Bao, L. Zou, Q. Yu, Y. Li, V. Kalosha, and L. Chen, "Accurate strain detection and localization with distributed Brillouin sensor based on a phenomenological signal processing approach," Proc. SPIE 6176, 61761C (2006).
[CrossRef]

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Figures (5)

Fig. 1
Fig. 1

Experimental setup. C, coupler (1–2: 95∕5, 3: 50∕50, 4: 99∕1); D, detector; PC, polarization controller; PS, polarization scrambler; DAS, data acquisition system.

Fig. 2
Fig. 2

Response curve of cos ( Ω Δ t ) versus Ω at the output of the mixer.

Fig. 3
Fig. 3

(Color online) Relationship between beat frequency and optical time delay.

Fig. 4
Fig. 4

(Color online) SNR versus pump power.

Fig. 5
Fig. 5

(Color online) Shift of the Brillouin spectrum when environmental temperature changes. Experimental 1 and Reconstruction 1: T = 23 ° C . Experimental 2 and Reconstruction 2: T = 0 ° C .

Tables (1)

Tables Icon

Table 1 Central Frequency, FWHM, and SNR of Brillouin Spectrum Along the Fiber With and Without Using a Lock-In Amplifier

Equations (48)

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1   GHz
100 μ s
32   dB
1   m
0.6   MHz
0.5 ° C
8 μ ε
1   GHz
1 2   MHz
( 10 5 )
< 100   MHz
60   MHz
30   dB
10   mW
32   dB
0.6 MHz
0.5 ° C
8 μ ε
10   ns
2   km
12.5   kHz
1550   nm
( Ω Δ t )
Ω Δ t
Ω Δ t
Δ t
Ω Δ t
Ω Δ t
Δ t
10880.8   MHz
250   kHz
50   kHz
1   GHz
10   ns
1   m
9   dBm
32   dB
0.6   MHz
0.5 ° C
( 23 ° C )
1   m
( 0 ° C )
27   MHz
23 ° C
1 ° C
( Ω Δ t )
T = 23 ° C
T = 0 ° C

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