Superluminescent diode monolithically integrated with novel Y-branch by bundle integrated waveguide for fiber optic gyroscope - art. no. 68380D

We have developed a novel InP-based, ridge-waveguide photonic integrated circuit (PIC), which consists of a 1.1-um wavelength Y-branch optical waveguide with low loss and improved far field pattern and a 1.3-um wavelength strained InGaAsP-InP multiple quantum-well superluminescent diode, with bundle integrated guide (BIG) as the scheme for monolithic integration. The simulations of BIG and Y-branches show low losses and improved far-field patterns, based on the beam propagation method (BPM). The amplified spontaneous emission of the device is up to 10 mW at 120 mA with no threshold and saturation. Spectral characteristics of about 30 nm width and less than I dB modulation are achieved using the built-in anti-lasing ability of Y-branch. The beam divergence angles in horizontal and vertical directions are optimized to as small as 12 degrees x8 degrees, resulting in good fiber coupling. The compactness, simplicity in fabrication, good superluminescent performance, low transmission loss and estimated low coupling loss prove the BIG and Y-branch method to be a feasible way for integration and make the photonic integrated circuit of Y-branch and superluminescent diode an promising candidate for transmitter and transceiver used in fiber optic gyroscope.

High efficiency fiber to waveguide optical coupler in silicon-on-insulator-based slot waveguides - art. no. 68310R

We propose a novel optical fiber-to-waveguide coupler for integrated optical circuits. The proper materials and structural parameters of the coupler, which is based on a slot waveguide, are carefully analyzed using a full-vectorial three dimensional mode solver. Because the effective refractive index of the mode in a silicon-on-insulator-based slot waveguide can be extremely close to that of the fiber, a highly efficient fiber-to-waveguide coupling application can be realized. For a TE-like mode, the calculated minimum mismatch loss is about 1.8dB at 1550nm, and the mode conversion loss can be less than 0.5dB. The discussion of the present state-of-the-art is also involved. The proposed coupler can be used in chip-to-chip communication.

Ground target detection, classification and sensor fusion in distributed fiber seismic sensor network - art. no. 683015

This paper describes the ground target detection, classification and sensor fusion problems in distributed fiber seismic sensor network. Compared with conventional piezoelectric seismic sensor used in UGS, fiber optic sensor has advantages of high sensitivity and resistance to electromagnetic disturbance. We have developed a fiber seismic sensor network for target detection and classification. However, ground target recognition based on seismic sensor is a very challenging problem because of the non-stationary characteristic of seismic signal and complicated real life application environment. To solve these difficulties, we study robust feature extraction and classification algorithms adapted to fiber sensor network. An united multi-feature (UMF) method is used. An adaptive threshold detection algorithm is proposed to minimize the false alarm rate. Three kinds of targets comprise personnel, wheeled vehicle and tracked vehicle are concerned in the system. The classification simulation result shows that the SVM classifier outperforms the GMM and BPNN. The sensor fusion method based on D-S evidence theory is discussed to fully utilize information of fiber sensor array and improve overall performance of the system. A field experiment is organized to test the performance of fiber sensor network and gather real signal of targets for classification testing.

High-performance multiplexed vibration sensor system based on fiber lasers - art. no. 683019

This paper describes a high-performance multiplexed vibration sensor system using fiber lasers. A serial vibration sensor array consists of four short cavity fiber lasers. The system employs a single, polarization-insensitive, unbalanced Michelson interferometer to translate individual laser wavelength shifts induced by vibration signals into interferometer phase shifts. A dense wavelength division demultiplexor (DWDM) with high channel isolation is inserted to demultiplex each laser signal as a wavelength filter. Finally, a digital phase demodulator based on the phase generated carrier technique is used to achieve high-resolution interrogation. Experimental results show that no observable crosstalk is measured on the output channels, and the minimal detectable acceleration of this system is similar to 200ng/root Hz at 250Hz, which is fundamentally limited by the frequency noise of the lasers.

A New Technique for Side Pumping of Double-Clad Fiber Lasers

We report a new technique, called SAP, for side pumping of double-clad, rare-earth-doped fiber lasers using fiber-coupled pump sources. The highest coupling efficiency can even exceed 92% in theory with this structure.

Unattended ground sensor system based on fiber optic disk accelerometer

The basic principle and critical characteristics of unattended ground sensors (UGS) based on fiber optic disk accelerometers are introduced. Mechanical principles of fiber optic disk accelerometers (FODA) and calculation methods are presented. An FODA with a high sensitivity of 120rad/g and a resonance frequency of 300Hz is designed and used for detection in military affair.

Investigation on pressure sensitivity of fiber optic mandrel hydrophone - art. no. 659544

Pressure sensitivity of the fiber optic mandrel hydrophone is analyzed in this paper. Based on the theory of elasticity, the mechanism of the pressure response is studied. The influence of the optical fiber on the compliant mandrel on the pressure response is taken into consideration for the first time. The radial deformation of the mandrel under the pressure of the fiber optic and the underwater pressure is analyzed in details. Based on the theory of photo-elasticity, the phase shift of the Mach-Zehnder interferometer is given. The pressure sensitivity is evaluated both theoretically and experimentally, and the results show a good correlation between the theoretical and experimental results.