Brillouin three-loop narrow-linewidth fiber laser with low insertion loss

Abstract

The invention discloses a Brillouin three-loop narrow-linewidth fiber laser with low insertion loss. The Brillouin gain effect of an optical fiber, the Brillouin narrowing effect and the wiener effect are applied to the Brillouin fiber laser. The Brillouin fiber laser comprises a narrow-linewidth single-frequency continuous laser, an erbium-doped optical fiber amplifier, a polarization controller, an optical circulator, an optical divider, a single-mode optical fiber, an unpumped erbium-doped optical fiber, a photoelectric modulator, a signal generator, a photoelectric detector and a spectrum analyzer. The laser is characterized in that the proper length of the three-loop optical fiber with low insertion loss is selected, thresholds and line width characteristics of the Brillouin fiber laser can be optimized, the system cost is effectively reduced, and the laser is measured by a line width testing system, so that the Brillouin single-longitudinal-mode laser with the threshold of 26mW and the line width less than 300Hz is obtained.

Description

technical field [0001] The present invention relates to a kind of optical fiber laser, especially a kind of narrow line width single-frequency continuous laser, erbium-doped fiber amplifier, polarization controller, optical circulator, optical splitter, single-mode optical fiber, unpumped erbium-doped optical fiber A three-loop low-threshold narrow-linewidth Brillouin fiber laser with an optoelectronic modulator, signal generator, photodetector, and spectrum analyzer. Background technique [0002] Because stimulated Brillouin scattering has the characteristics of narrow bandwidth and low noise, it is widely used in distributed optical fiber sensing, narrowband low noise amplifier, narrow linewidth fiber laser and microwave photon generator, etc., especially, from 1976 Hill et al. After the researchers (Appl. Phys. Lett. 1976, 28(10): 608-609.) proposed the Brillouin fiber laser for the first time, due to the advantages of the narrow linewidth, low threshold and low cost of t...

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Problems solved by technology

Researchers such as Yong used an asymmetric Mach-Zehnder interference structure to obtain a single longitudinal mode output with a linewidth of less than 1kHz (J. Lightw. Technol., vol. 21, no. 2, pp. 546–554, Feb. 2003) , through the asymmetric Mach-Zehnder interference to filter out the pump light and the Brillouin laser respectively, because there is only the Brillouin laser in the resonator, so the cavity loss can be effectively reduced, although this structure is simple and uses a commercial DFB Laser, but this structure also needs a high-precision (0.01 ℃) constant temperature box to ensure its filtering characteristics; Shen and other researchers used a Bragg grating to form a Fab cavity to achieve an 11GHz microwave signal (J. Lightwave Technol. 23, 1860 -1865,2005.), but it is necessary to precisely adjust the reflectivity of the FBG to obtain a narrow linewidth output, which virtually increases the loss of the resonator loop; researchers such as Geng used PDH (Pound-Drever-Hall) Stabilized system (IEEE Photon. Technol. Lett. vol. 18, no. 17, pp. 1813–1815, Sep. 1, 2006.), achieving a theoretical linewidth value of 75Hz, but this configuration is complex and costly

The above-mentioned experimental devices have a common problem, that is, the ring length of the resonator is in the range of 10m~20m, which will limit the further optimization of the linewidth and threshold of the Brillouin fiber laser

[0004] In view of the limitation of ring length, researchers such as Chen extended the resonant cavity length to 500m high nonlinear optical fiber as a medium to provide Brillouin gain (Appl. Phys. B, vol. 107, no. 3, pp . 791–794, 2012.), together with an adaptive ultra-narrow band-pass filter, realized single longitudinal mode laser output, but did not measure its real line width value, and this adaptive ultra-narrow band-pass filter The pump light power needs to be precisely controlled, which increases the cavity loss and cannot achieve the effect of optimizing the laser threshold. At the same time, the 500m high nonlinear fiber is also very expensive

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