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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 20, Iss. 16 — Jul. 30, 2012
  • pp: 17695–17700
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Long-distance fiber-optic point-sensing systems based on random fiber lasers

Z. N. Wang, Y. J. Rao, H. Wu, P. Y. Li, Y. Jiang, X. H. Jia, and W. L. Zhang  »View Author Affiliations


Optics Express, Vol. 20, Issue 16, pp. 17695-17700 (2012)
http://dx.doi.org/10.1364/OE.20.017695


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Abstract

We find that the random fiber laser (RFL) without point-reflectors is a temperature-insensitive distributed lasing system for the first time. Inspired by such thermal stability, we propose the novel concept of utilizing the RFL to achieve long-distance fiber-optic remote sensing, in which the RFL offers high-fidelity and long-distance transmission for the sensing signal. Two 100km fiber Bragg grating (FBG) point-sensing schemes based on RFLs are experimentally demonstrated using the first-order and the second-order random lasing, respectively, to verify the concept. Each sensing scheme can achieve >20dB optical signal-to-noise ratio (OSNR) over 100km distance. It is found that the second-order random lasing scheme has much better OSNR than that of the first-order random lasing scheme due to enhanced lasing efficiency, by incorporating a 1455nm FBG into the lasing cavity.

© 2012 OSA

1. Introduction

Since the demonstration of the distributed random feedback within telecom fibers generating stable continuous-wave (CW) lasing output [1

1. S. K. Turitsyn, S. A. Babin, A. E. El-Taher, P. Harper, D. V. Churkin, S. I. Kablukov, J. D. Ania-Castañón, V. Karalekas, and E. V. Podivilov, “Random distributed feedback fiber laser,” Nat. Photonics 4(4), 231–235 (2010). [CrossRef]

], this kind of random lasers based on fibers have attracted a lot of attention because of their outstanding advantages, such as long-distance signal delivery ability, ultra-low intensity noise, cavity simplicity and high lasing efficiency, etc. Therefore, it was considered to have significant impact on fiber-optic communication and sensing, etc [2

2. A. A. Fotiadi, “Random lasers: An incoherent fibre laser,” Nat. Photonics 4(4), 204–205 (2010). [CrossRef]

]. Valuable work has been made to study such type of random fiber lasers (RFLs) and various unique physical features have been reported [3

3. D. V. Churkin, S. A. Babin, A. E. El-Taher, P. Harper, S. I. Kablukov, V. Karalekas, J. D. Ania-Castañón, E. V. Podivilov, and S. K. Turitsyn, “Raman fiber lasers with a random distributed feedback based on Rayleigh scattering,” Phys. Rev. A 82(3), 033828 (2010). [CrossRef]

10

10. A. R. Sarmani, M. H. Abu Bakar, A. A. A. Bakar, F. R. Adikan, and M. A. Mahdi, “Spectral variations of the output spectrum in a random distributed feedback Raman fiber laser,” Opt. Express 19(15), 14152–14159 (2011). [CrossRef] [PubMed]

]. However, there are many more features of the random lasing mechanism, in particular, its potential applications for long-distance sensing, yet to be fully explored, in order to essentially achieve the goal of improving the performance of the sensing system, such as extension of sensing distance or enhancement of optical signal-to-noise ratio (OSNR), etc.

2. Thermal stability of the RFL

To study the temperature response of the spectrum of the RFL, the 100km SMF is put into a temperature controlled chamber and the remaining components of the RFL setup is kept in room temperature. The pump power is set to be 1.7W. The chamber temperature is adjusted from −40°C to + 50°C with a 10°C step. During each measurement the spectrum is recorded when the in-chamber temperature reaches the set value for at least 25 minutes. Figure 2(a)
Fig. 2 (a) Temperature response of the lasing wavelength; (b) the output spectra at −40°C and + 50°C, respectively.
shows the variation of the central wavelength of the left lasing peak according to the surrounding temperature, and Fig. 2(b) compares the spectra at −40°C and + 50°C . It can be clearly seen that the lasing wavelength is insensitive to the temperature change. It is also noted that the mechanical vibration during the heating procedure will not destabilize the lasing output.

3. Stable remote point-sensing with the RFL

The temperature insensitivity enables the RFL to be a good candidate for remote temperature point-sensing. A FBG with a central wavelength at 1454 nm and 98% reflectivity is spliced to the end of the 100km fiber span, and it acts a point mirror. Due to the dominant mode-selection effect introduced by the FBG, the output spectrum of the RFL exhibits single highly pronounced peak, as shown in Fig. 3(a)
Fig. 3 (a) The output spectral shape corresponded to 1.6W pump power input in room temperature; (b) temperature response of the central lasing wavelength.
. The OSNR of the peak is ~20dB, and the bandwidth is ~0.27nm. To study the temperature response of the whole sensing system, two measurements are carried out: 1) at first only the FBG is put inside the temperature controlled chamber; 2) then the 100km fiber is put into the chamber as well. As the central Bragg wavelength of the FBG is shifted under the temperature variation, the central wavelength of the lasing peak is shifted accordingly. Figure 3(b) compares the temperature response of the central lasing wavelength in both measurements. It can be seen that the two data sets are well matched. In this regime the 100km fiber span is both a distributed lasing medium and part of the sensing system, within which only the FBG is temperature sensitive while the distributed lasing cavity is intrinsic temperature-insensitive. The thermal-stability and the ultra-long power delivery ability made the RFL an accurate remote temperature sensing system. It should be noted that with current fiber length a high OSNR of 20dB is maintained, therefore the ultimate limit of such a sensing system can be significantly beyond 100km.

4. Remote sensing utilizing the second-order random lasing and discussions

Figure 4
Fig. 4 The setup of the RFL with half-open cavity
shows the experimental setup of the RFL utilizing the second-order random lasing for the long-distance point-sensing. The 1365nm pump source is launched into a 100km fiber span through a 1365/1461nm wavelength division multiplexer (WDM) and a 1455nm FBG, and the 1455nm FBG is used as a point mirror with high-reflectivity. The light-waves propagating towards the pump side is tapped out through a 1:99 coupler for spectral analysis, and those arriving at another end (far-end) of the fiber span are also monitored. A 1560nm FBG and a 1563nm FBG will be successively attached at the far-end of the fiber span as sensing heads, which will be discussed next.

As the pump power is increased, the system starts to lase as the distributed Rayleigh backscattering along the fiber span together with the 1455nm FBG forms a sufficient feedback per round trip. As shown in Fig. 5(a)
Fig. 5 Far-end spectra of the RFL (1455nm FBG plus 100km SMF) with different pump power.
, the generated first-order random lasing is located at 1455nm, corresponding to the FBG wavelength and within the Raman gain curve of the 1365nm pump laser. As the pump power is increased further, the second-order random lasing located at the C-band appears. When the 1455nm lasing power is near the threshold level for the generation of the C-band lasing, the spectrum of the second-order lasing shows random spikes and dips, as shown in Fig. 5(b). As the 1455nm lasing power is well above the threshold level, the optical spectrum becomes stabilized. As indicated in Fig. 5(c), a C-band continuous-wave (CW) radiation is generated as the stable second-order random lasing. It should be noted that the direct pump source of the C-band CW is the 1455nm light-wave (i. e., the first-order random lasing), and the lasing cavity for the C-band CW is fully distributed, as the 1455nm can be considered transparent for the C-band light-wave.

To demonstrate the remote-sensing ability of the system, a FBG with a central wavelength at 1560 nm is spliced to the end of the 100km fiber span, and it acts as a sensing head. Due to the dominant wavelength-selection effect introduced by the 1560nm FBG, the spectrum of the second-order lasing exhibits highly pronounced peak, as shown in Fig. 6(a)
Fig. 6 (a) Near-end spectrum; (b) temperature response of the central wavelength. (Inset: the near-end spectrum when a 1563nm FBG is attached after the 1560nm FBG)
. The OSNR of the peak is more than 35dB, and the bandwidth is ~0.26nm. To study the temperature response of the spectrum of the 1560nm spike, the 1560nm FBG is put into a temperature controlled chamber and the remaining components of the RFL setup is kept in room temperature. The chamber temperature is adjusted from −20°C to + 50°C with a 10°C step. Again, during each measurement the spectrum is recorded when the in-chamber temperature reached the set value for at least 25 minutes. Figure 6(b) shows the variation of the central wavelength of the lasing spike according to the chamber temperature. It can be clearly seen that the change of the lasing wavelength is linear to the temperature change.

5. Conclusions

We demonstrate that the RFL with fully distributed random feedback has the unique thermal stability compared with traditional fiber lasers. Base on such a merit and the ability of long-distance power delivery, we proposed the novel concept of utilizing the first-order and the second-order random fiber lasers to form long-distance point-sensing systems. Two 100km FBG point-sensing systems are experimentally demonstrated to verify such a concept. The first-order random lasing scheme can observe 20dB OSNR, while the second-order random lasing scheme can observe 35dB OSNR. The observed wavelength shift is solely dependent on the Bragg wavelength shift of the sensing FBG remotely located. Neither the long-span fiber as the lasing cavity, nor the near-end FBG used for enhancing the lasing efficiency, will contribute to the monitored wavelength shift, proving that such a novel long-distance point-sensing system is very stable. This work may open a window for realizing a new generation of simple and reliable long-distance point-sensing systems.

Acknowledgement

The authors would like to thank Dr. X. F. Chen and Prof. L. Zhang in Aston University for providing the 1454nm FBGs. This work is partially funded by NSFC No. 61106045.

References and links

1.

S. K. Turitsyn, S. A. Babin, A. E. El-Taher, P. Harper, D. V. Churkin, S. I. Kablukov, J. D. Ania-Castañón, V. Karalekas, and E. V. Podivilov, “Random distributed feedback fiber laser,” Nat. Photonics 4(4), 231–235 (2010). [CrossRef]

2.

A. A. Fotiadi, “Random lasers: An incoherent fibre laser,” Nat. Photonics 4(4), 204–205 (2010). [CrossRef]

3.

D. V. Churkin, S. A. Babin, A. E. El-Taher, P. Harper, S. I. Kablukov, V. Karalekas, J. D. Ania-Castañón, E. V. Podivilov, and S. K. Turitsyn, “Raman fiber lasers with a random distributed feedback based on Rayleigh scattering,” Phys. Rev. A 82(3), 033828 (2010). [CrossRef]

4.

A. E. El-Taher, M. Alcon-Camas, S. A. Babin, P. Harper, J. D. Ania-Castañón, and S. K. Turitsyn, “Dual-wavelength, ultralong Raman laser with Rayleigh-scattering feedback,” Opt. Lett. 35(7), 1100–1102 (2010). [CrossRef] [PubMed]

5.

S. A. Babin, A. E. El-Taher, P. Harper, E. V. Podivilov, and S. K. Turitsyn, “Tunable random fiber laser,” Phys. Rev. A 84(2), 021805 (2011). [CrossRef]

6.

I. D. Vatnik, D. V. Churkin, S. A. Babin, and S. K. Turitsyn, “Cascaded random distributed feedback Raman fiber laser operating at 1.2 μm,” Opt. Express 19(19), 18486–18494 (2011). [CrossRef] [PubMed]

7.

A. E. El-Taher, P. Harper, S. A. Babin, D. V. Churkin, E. V. Podivilov, J. D. Ania-Castanon, and S. K. Turitsyn, “Effect of Rayleigh-scattering distributed feedback on multiwavelength Raman fiber laser generation,” Opt. Lett. 36(2), 130–132 (2011). [CrossRef] [PubMed]

8.

A. M. R. Pinto, O. Frazão, J. L. Santos, and M. Lopez-Amo, “Multiwavelength raman fiber lasers using Hi-Bi photonic crystal fiber loop mirrors combined with random cavities,” J. Lightwave Technol. 29(10), 1482–1488 (2011). [CrossRef]

9.

D. V. Churkin, A. E. El-Taher, I. D. Vatnik, J. D. Ania-Castañón, P. Harper, E. V. Podivilov, S. A. Babin, and S. K. Turitsyn, “Experimental and theoretical study of longitudinal power distribution in a random DFB fiber laser,” Opt. Express 20(10), 11178–11188 (2012). [CrossRef] [PubMed]

10.

A. R. Sarmani, M. H. Abu Bakar, A. A. A. Bakar, F. R. Adikan, and M. A. Mahdi, “Spectral variations of the output spectrum in a random distributed feedback Raman fiber laser,” Opt. Express 19(15), 14152–14159 (2011). [CrossRef] [PubMed]

11.

M. Fernandez-Vallejo and M. Lopez-Amo, “Optical fiber networks for remote fiber optic sensors,” Sensors (Basel) 12(4), 3929–3951 (2012). [CrossRef] [PubMed]

12.

Y. J. Rao, “In-fibre Bragg grating sensors,” Meas. Sci. Technol. 8(4), 355–375 (1997). [CrossRef]

13.

Y. J. Rao, “Recent progress in applications of in-fibre Bragg grating sensors,” Opt. Lasers Eng. 31(4), 297–324 (1999). [CrossRef]

14.

Y. J. Rao, “OFS research over the last 10 years at CQU & UESTC,” Photon. Sens. 2(2), 97–117 (2012). [CrossRef]

OCIS Codes
(060.2370) Fiber optics and optical communications : Fiber optics sensors
(140.3510) Lasers and laser optics : Lasers, fiber
(290.5870) Scattering : Scattering, Rayleigh
(290.5910) Scattering : Scattering, stimulated Raman
(060.3735) Fiber optics and optical communications : Fiber Bragg gratings

ToC Category:
Sensors

History
Original Manuscript: May 9, 2012
Revised Manuscript: July 15, 2012
Manuscript Accepted: July 16, 2012
Published: July 19, 2012

Citation
Z. N. Wang, Y. J. Rao, H. Wu, P. Y. Li, Y. Jiang, X. H. Jia, and W. L. Zhang, "Long-distance fiber-optic point-sensing systems based on random fiber lasers," Opt. Express 20, 17695-17700 (2012)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-20-16-17695


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References

  1. S. K. Turitsyn, S. A. Babin, A. E. El-Taher, P. Harper, D. V. Churkin, S. I. Kablukov, J. D. Ania-Castañón, V. Karalekas, and E. V. Podivilov, “Random distributed feedback fiber laser,” Nat. Photonics4(4), 231–235 (2010). [CrossRef]
  2. A. A. Fotiadi, “Random lasers: An incoherent fibre laser,” Nat. Photonics4(4), 204–205 (2010). [CrossRef]
  3. D. V. Churkin, S. A. Babin, A. E. El-Taher, P. Harper, S. I. Kablukov, V. Karalekas, J. D. Ania-Castañón, E. V. Podivilov, and S. K. Turitsyn, “Raman fiber lasers with a random distributed feedback based on Rayleigh scattering,” Phys. Rev. A82(3), 033828 (2010). [CrossRef]
  4. A. E. El-Taher, M. Alcon-Camas, S. A. Babin, P. Harper, J. D. Ania-Castañón, and S. K. Turitsyn, “Dual-wavelength, ultralong Raman laser with Rayleigh-scattering feedback,” Opt. Lett.35(7), 1100–1102 (2010). [CrossRef] [PubMed]
  5. S. A. Babin, A. E. El-Taher, P. Harper, E. V. Podivilov, and S. K. Turitsyn, “Tunable random fiber laser,” Phys. Rev. A84(2), 021805 (2011). [CrossRef]
  6. I. D. Vatnik, D. V. Churkin, S. A. Babin, and S. K. Turitsyn, “Cascaded random distributed feedback Raman fiber laser operating at 1.2 μm,” Opt. Express19(19), 18486–18494 (2011). [CrossRef] [PubMed]
  7. A. E. El-Taher, P. Harper, S. A. Babin, D. V. Churkin, E. V. Podivilov, J. D. Ania-Castanon, and S. K. Turitsyn, “Effect of Rayleigh-scattering distributed feedback on multiwavelength Raman fiber laser generation,” Opt. Lett.36(2), 130–132 (2011). [CrossRef] [PubMed]
  8. A. M. R. Pinto, O. Frazão, J. L. Santos, and M. Lopez-Amo, “Multiwavelength raman fiber lasers using Hi-Bi photonic crystal fiber loop mirrors combined with random cavities,” J. Lightwave Technol.29(10), 1482–1488 (2011). [CrossRef]
  9. D. V. Churkin, A. E. El-Taher, I. D. Vatnik, J. D. Ania-Castañón, P. Harper, E. V. Podivilov, S. A. Babin, and S. K. Turitsyn, “Experimental and theoretical study of longitudinal power distribution in a random DFB fiber laser,” Opt. Express20(10), 11178–11188 (2012). [CrossRef] [PubMed]
  10. A. R. Sarmani, M. H. Abu Bakar, A. A. A. Bakar, F. R. Adikan, and M. A. Mahdi, “Spectral variations of the output spectrum in a random distributed feedback Raman fiber laser,” Opt. Express19(15), 14152–14159 (2011). [CrossRef] [PubMed]
  11. M. Fernandez-Vallejo and M. Lopez-Amo, “Optical fiber networks for remote fiber optic sensors,” Sensors (Basel)12(4), 3929–3951 (2012). [CrossRef] [PubMed]
  12. Y. J. Rao, “In-fibre Bragg grating sensors,” Meas. Sci. Technol.8(4), 355–375 (1997). [CrossRef]
  13. Y. J. Rao, “Recent progress in applications of in-fibre Bragg grating sensors,” Opt. Lasers Eng.31(4), 297–324 (1999). [CrossRef]
  14. Y. J. Rao, “OFS research over the last 10 years at CQU & UESTC,” Photon. Sens.2(2), 97–117 (2012). [CrossRef]

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