Random distributed feedback fibre lasers

Random fiber lasers blend together attractive features of traditional random lasers, such as low cost and simplicity of fabrication, with high-performance characteristics of conventional fiber lasers, such as good directionality and high efficiency. Low coherence of random lasers is important for speckle-free imaging applications. The random fiber laser with distributed feedback proposed in 2010 led to a quickly developing class of light sources that utilize inherent optical fiber disorder in the form of the Rayleigh scattering and distributed Raman gain. The random fiber laser is an interesting and practically important example of a photonic device based on exploitation of optical medium disorder. We provide an overview of recent advances in this field, including high-power and high-efficiency generation, spectral and statistical properties of random fiber lasers, nonlinear kinetic theory of such systems, and emerging applications in telecommunications and distributed sensing.

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Recent advances in fundamentals and applications of random fiber lasers

Lasing in nanocomposite random media

Narrow-band emission of spectral width down to ~0.05 nm line-width is achieved in the random distributed feedback fiber laser employing narrow-band fiber Bragg grating or fiber Fabry-Perot interferometer filters. The observed line-width is ~10 times less than line-width of other demonstrated up to date random distributed feedback fiber lasers. The random DFB laser with Fabry-Perot interferometer filter provides simultaneously multi-wavelength and narrow-band (within each line) generation with possibility of further wavelength tuning.

Narrow-band generation in random distributed feedback fiber laser.

In this paper, we make a comprehensive study on a highly efficient half-open cavity design for high power random fiber laser (RFL). With the theoretical analysis, we optimize the cavity's fiber length for getting higher output power within the scheme, i.e., shorter fiber length is preferred for efficiently harvesting the first order random lasing at the open end of the cavity. As the verification of the theory, we experimentally demonstrate a high output power (7 W), highly efficient (70% optical conversion efficiency) RFL working at 1140 nm, using 10 W 1090 nm laser as the pump source and only 1 km standard single-mode fiber as the distributed cavity.

High Power Random Fiber Laser With Short Cavity Length: Theoretical and Experimental Investigations

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.

Long-distance fiber-optic point-sensing systems based on random fiber lasers

In this paper, we experimentally demonstrate a novel configuration of multiwavelength Brillouin–Raman random fiber laser (MBRRFL) utilizing a half-open cavity. The laser resonator is formed by fiber loop mirror at the Brillouin pump (BP) side and random distributed Rayleigh backscattering in a 10 km dispersion compensating fiber. As a result, we are able to obtain a flat amplitude bandwidth of 16.8 nm from 1,550.0 to 1,566.8 nm built-in 210 uniform Brillouin Stokes lines with 0.08 nm spacing and an average OSNR of 13.5 dB. We also studied the influence of BP power and wavelength on the MBRRFL’s performance. Furthermore, comparing with the open cavity configuration, the discrepancies in power level and linewidth between neighboring channels are overcome by using the half-open cavity.

Flat amplitude multiwavelength Brillouin-Raman random fiber laser with a half-open cavity

We experimentally demonstrate a 42nm flat-amplitude multiwavelength Brillouin-Raman fiber laser with 525 Stokes lines by combining dispersion compensating fiber and standard single mode fiber. In addition, the discrepancies in power level and linewidth between neighboring channels are diminished in this scheme.

Flat-amplitude multiwavelength Brillouin-Raman fiber laser in a linear cavity utilizing cascaded fibers

The novel concept of utilizing the second-order random fiber laser (RFL) to realize long-distance fiber-optic pointsensing systems is proposed. The sensing system consists of a pump laser, a fiber Bragg grating (FBG) at the pump side and 100km single mode fiber (SMF), and another FBG at the end of the SMF. The first FBG is used to enhance the lasing efficiency, and the second FBG is use as the remotely-located sensing head. The Bragg wavelengths of the two FBGs correspond to the first-order and the second-order random lasing spectrum, respectively. Its ability for remote temperature sensing is experimentally demonstrated. © (2012) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

Peiyun Li

Papers

Long-distance fiber-optic point-sensing systems based on random fiber lasers

Flat amplitude multiwavelength Brillouin-Raman random fiber laser with a half-open cavity

Flat-amplitude multiwavelength Brillouin-Raman fiber laser in a linear cavity utilizing cascaded fibers

Long-distance fiber-optic point-sensing systems based on the second-order random fiber laser