Analysis of bandwidth-reduced local oscillator in Brillouin optical time domain reflectometry

Author

Hao Yun-qi ; Ye Qing ; Pan Zheng-qing ; Cai Hai-wen ; Qu Rong-hui

Author_Institution

Shanghai Inst. of Opt. & Fine Mech., Shanghai, China

fYear

2011

fDate

13-16 Nov. 2011

Firstpage

1

Lastpage

7

Abstract

A local oscillator for coherent detection of backward Brillouin scattering in Brillouin optical time domain reflectometry (BOTDR) has been analyzed. A ring Brillouin fiber laser, whose Brillouin gain media is 70m high-nonlinear-fiber (HNLF), is used as local oscillator of coherent detection. The BFL operates at 1549.06nm red-shifted 0.084nm from the pump laser. As to Brillouin light, The detection frequency is reduced from ~11GHz of direct detection to ~420MHz of heterodyne detection in this paper. Self-lasing cavity-modes of BFL impose the “burr” intervalled at 2.5MHz on the frequency domain analysis of the beat-frequency siganl. Signal-to-noise ratio (SNR) of beat-frequency signal decreases greatly, resulting to Lorentzian fitting with error. By adjusting variable optical attenuator (VOA) to increase the cavity loss in the fiber ring cavity, the self-lasing cavity-modes will be eliminated and a stable Brillouin laser will be obtained. The frequency estimation accuracy is improved greatly.

Keywords

Brillouin spectra; fibre lasers; fibre optic sensors; heterodyne detection; laser cavity resonators; optical attenuators; optical fibre losses; optical pumping; ring lasers; time-domain reflectometry; Brillouin laser; Brillouin light; Brillouin optical time domain reflectometry; Lorentzian fitting; backward Brillouin scattering; bandwidth-reduced local oscillator; beat-frequency signal; burr intervalled; cavity loss; coherent detection; fiber ring cavity; frequency 2.5 MHz; frequency domain analysis; heterodyne detection; high-nonlinear-fiber; pump laser; red- hift; ring Brillouin fiber laser; self-lasing cavity-modes; signal-to-noise ratio; variable optical attenuator; wavelength 1549.06 nm; Frequency estimation; Optical coupling; Optical mixing; Optical modulation; Optical pumping; Optical sensors; BOTDR; local oscillator; self-lasing cavity modes;

fLanguage

English

Publisher

ieee

Conference_Titel

Communications and Photonics Conference and Exhibition, 2011. ACP. Asia

Conference_Location

Shanghai

ISSN

2162-108X

Print_ISBN

978-0-8194-8961-6

Type

conf

DOI

10.1117/12.904179

Filename

6210900