Yiyang Luo

Optical chaos and hybrid WDM/TDM based large capacity quasi-distributed sensing network with real-time fiber fault monitoring.

Optical chaos and hybrid WDM/TDM based large capacity quasi-distributed sensing network with real-time fiber fault monitoring is proposed and proof-of-concept demonstrated. The multiplexing capacity can promisingly reach to 512.

Group-velocity-locked vector soliton molecules in fiber lasers

Physics phenomena of multi-soliton complexes have enriched the life of dissipative solitons in fiber lasers. By developing a birefringence-enhanced fiber laser, we report the first experimental observation of group-velocity-locked vector soliton (GVLVS) molecules. The birefringence-enhanced fiber laser facilitates the generation of GVLVSs, where the two orthogonally polarized components are coupled together to form a multi-soliton complex. Moreover, the interaction of repulsive and attractive forces between multiple pulses binds the particle-like GVLVSs together in time domain to further form compound multi-soliton complexes, namely GVLVS molecules. By adopting the polarization-resolved measurement, we show that the two orthogonally polarized components of the GVLVS molecules are both soliton molecules supported by the strongly modulated spectral fringes and the double-humped intensity profiles. Additionally, GVLVS molecules with various soliton separations are also observed by adjusting the pump power and the polarization controller.

M-OTDR sensing system based on 3D encoded microstructures

In this work, a quasi-distributed sensing scheme named as microstructured OTDR (M-OTDR) by introducing ultra-weak microstructures along the fiber is proposed. Owing to its relative higher reflectivity compared with the backscattered coefficient in fiber and three dimensional (3D) i.e. wavelength/frequency/time encoded property, the M-OTDR system exhibits the superiorities of high signal to noise ratio (SNR), high spatial resolution of millimeter level and high multiplexing capacity up to several ten thousands theoretically. A proof-of-concept system consisting of 64 sensing units is constructed to demonstrate the feasibility and sensing performance. With the help of the demodulation method based on 3D analysis and spectrum reconstruction of the signal light, quasi-distributed temperature sensing with a spatial resolution of 20 cm as well as a measurement resolution of 0.1 °C is realized.

Group velocity locked vector dissipative solitons in a high repetition rate fiber laser

Vectorial nature of dissipative solitons (DSs) with high repetition rate is studied for the first time in a normal-dispersion fiber laser. Despite the fact that the formed DSs are strongly chirped and the repetition rate is greater than 100 MHz, polarization locked and polarization rotating group velocity locked vector DSs can be formed under 129.3 MHz fundamental mode-locking and 258.6 MHz harmonic mode-locking of the fiber laser, respectively. The two orthogonally polarized components of these vector DSs possess distinctly different central wavelengths and travel together at the same group velocity in the laser cavity, resulting in a gradual spectral edge and small steps on the optical spectrum, which can be considered as an auxiliary indicator of the group velocity locked vector DSs. Moreover, numerical simulations well confirm the experimental observations and further reveal the impact of the net cavity birefringence on the properties of the formed vector DSs.

A Single Longitudinal Mode Fiber Ring Laser Based on Cascaded Microfiber Knots Filter

A single longitudinal mode (SLM) fiber ring laser based on a cascaded microfiber knots filter (CMKF) is proposed and demonstrated. The CMKF is consists of two microfiber knot resonators, which can cause a spatial mode beating interference deriving from high proportional evanescent field of microfiber and spectrum magnification function of Vernier effect, resulting in a passive narrow-band filter with the ability to generate stable SLM. Theoretical analysis and simulation are carried out to investigate the Vernier transmission spectrum of the CMKF and then the SLM principle. A narrow linewidth, high stability, and low-noise SLM lasing with a central wavelength of 1560.6 nm, a 3-dB bandwidth of less than 0.016 nm, and side mode suppression ratio better than 55 dB is achieved experimentally.

Sensitivity-controllable refractive index sensor based on reflective θ-shaped microfiber resonator cooperated with Vernier effect

In this paper, we report a sensitivity-controllable refractive index (RI) sensor based on a reflective θ-shaped microfiber resonator cooperated with Vernier effect. The θ-shaped microfiber resonator is a reflective all-fiber device with comb spectrum under weak coupling condition. By cascading it with a fiber Fabry-Perot interferometer, Vernier effect is generated to demodulate surrounding RI with enhanced sensitivity. Theoretical analysis reveals that RI sensitivity of the combined structure with Vernier effect is m times higher than the sensitivity of singular θ-shaped microfiber resonator. Moreover, by adjusting cavity length of the θ-shaped microfiber resonator, magnification factor M = (m + 1) can be tuned which enables the RI sensitivity to be controlled. Experimental result demonstrates that the RI sensitivity can be widely tuned from 311.77 nm/RIU (Reflective index unit) to 2460.07 nm/RIU when the cavity length of the θ-shaped microfiber resonator is adjusted from 9.4 mm to 8.7 mm. The θ-shaped microfiber resonator based all-fiber RI sensor featuring controllable sensitivity and compact size can be widely used for chemical and biological detections. The proposed scheme of generating Vernier effect also offers a universal idea to increase measurement sensitivity for optical fiber sensing structures with comb spectrum.

Quasi-Distributed Strain Sensing System Based on Optical Spectrum-Limited Chaos and CFBG Intensity Demodulation

We propose a quasi-distributed sensing system using optical spectrum-limited chaos for strain measurement with a high spatial resolution of locating. An optical bandpass filter is programmed in accordance with each sensor to implement the intensity demodulation of multiple chirped fiber Bragg gratings (FBGs). A cross-correlation algorithm is adopted in this sensing scheme. Consequently, strain sensing and locating can be simultaneously demodulated by the relative amplitude change (RAC) and time delay of a certain cross-correlation peak. Meanwhile, fiber fault monitoring can also be implemented by the cross-correlation algorithm, and an additional optical passband is reserved for sufficient breakpoint testing optical power. The proof-of-concept experiment demonstrates that the strain sensitivity reaches 0.12% RAC/

Observation of Wavelength Tuning and Bound States in Fiber Lasers

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Liquid level optical fiber sensor based on enhanced multimode interference

, and the spatial resolution is up to 3.3 cm. Finally, the performance of fiber fault monitoring is also demonstrated.

High sensitive and selective Escherichia coli detection using immobilized optical fiber microprobe

We report an experimental observation of wavelength tuning and bound states in fiber lasers. A Mach-Zehnder interferometer (MZI) is adopted as an intra-cavity tunable filter to realize large-scale wavelength tuning and bandwidth controlling. By finely manipulating the MZI and intra-cavity polarization state, continuous wavelength-tunable operation from 1550.7 nm to 1580.8 nm is achieved. Meanwhile, the spectral bandwidth varying from 1.85 nm to 3.41 nm is also controlled by broadening the free spectrum range (FSR) of the MZI. Additionally, with modest polarization adjustment, both tightly and loosely bound states are experimentally observed, which can be validated by the numerical simulations. The results indicate that the proposed fiber laser is attractive for telecommunication systems, on account that the tuning feature can be applied to wavelength-division multiplexer (WDM) and the various soliton bound states could contribute to the high-level modulation format.