Huizu Lin

Multiple Reflections Induced Crosstalk in Inline TDM Fiber Fabry-Perot Sensor System Utilizing Phase Generated Carrier Scheme

An inline time-division multiplexing fiber Fabry-Perot (TDM-FFP) sensor system based on low-reflectivity fiber Bragg gratings (FBGs) is ideally suited to many applications. The intrinsic multiple reflections crosstalk (MRC) phenomenon in the inline TDM-FFP sensor system is a serious problem that limits the multiplexing number of sensors, which hindrances its practical applications. In this paper, a detailed analysis of the MRC in the inline TDM-FFP sensor system using phase generated carrier (PGC) scheme is reported. The equations of the interference intensity in the inline TDM-FFP sensor system with two sensors are deduced. The characteristics of the MRC are theoretically analyzed according to the equations and experimentally demonstrated. Finally, the instability of the MRC induced by random phase relationships of the sensors is analyzed using statistical method. The experimental results show that the crosstalk from the first sensor to the second sensor is ranged from 36.48 to 67.64 dB and to the third sensor is ranged from 16.02 to 60.64 dB.

Spectral character of polarization-maintaining fiber Bragg grating interrogated by different linearly polarized light

Abstract. Fiber Bragg grating written in polarization-maintaining fiber is strongly polarization-dependent, and its spectral character depends on the polarization state of light that interrogates the grating. We propose a novel and practical method to test the spectra character of the polarization-maintaining fiber Bragg grating (PM-FBG) interrogated by a linearly polarized light with a different azimuth for the first time. We specially designed a splice with a different angle in the system to alter the azimuth of the input linearly polarized light. Using this method, we got the transmission and reflection spectra of the PM-FBG measured at different splice angles and then the experimental results were analyzed originally. The analysis result shows that the relationship between the transmission dip and the splice angle obeys the Gaussian distribution. The reflectivity of the two wavelengths of the PM-FBG depends on the azimuth of the input linearly polarized light.

90-deg splicing error control in polarization maintaining fiber resonator based on white-light interferometry

Polarization fluctuation in polarization maintaining fiber (PMF) resonator is one of the major noise sources in resonant fiber optic gyroscope (R-FOG). 90-deg polarization-axis rotated splicing in R-FOG is an effective way to suppress the polarization-fluctuation induced noise. 90-deg polarization-axis rotated splicing error influences the noise suppression effect. Here, a polarization-coupling testing system based on white-light interferometry is designed to control 90-deg splicing error in double-coupler PMF resonator first time and a result of 0.37-deg splicing error is obtained for the first time. Then the resonant characteristics of the double-coupler PMF resonator are tested using the saw-tooth waveform scanning method. The finesse of this double-coupler PMF resonator is 24.0 and the phase interval of the two eigenstates of polarization (ESOPs) is π.

Input-polarization-induced phase noise in interferometric fiber-optic sensors and its reduction using polarization diversity receivers

The random fluctuation in the input polarization to an interferometric optical fiber sensor can result in not only the variation of the visibility but also the generation of excess phase noise in the output. In this paper, the relationship between the visibility and polarization-induced phase noise coefficient is described and theoretically confirmed. The use of polarization diversity receivers (PDR) to reduce phase noise is theoretically and experimentally demonstrated. The result shows that the PDR that improves the visibility can reduce the polarization-induce phase noise and the signal can be correctly demodulated.

An integrated polarization-holding fiber polarizing grating based on side-polishing and metal film coating techniques

Optical fiber polarizer and grating are two widely used fiber components and in this paper we proposed an integrated polarizing grating fabricated in polarization-holding fiber, which achieves reflecting and polarizing functions simultaneously. A D-shaped multilayer grating waveguide model was established and the linearly polarizing principles in both reflection and transmission ports were presented. An integrated polarization-holding fiber polarizing grating was fabricated and the laser polarization states of incidence, reflection and transmission were all measured, showing that this integrated fiber device can achieve reflecting and polarizing functions simultaneously. The discrimination between the reflection and transmission was also investigated.

Visibility properties of the interferometric optical fiber sensors using polarization scrambling

An interferometric optical fiber sensor relies on the coherent mixing of the optical signals, which is strongly polarization dependent. Random fluctuations in the input state of polarization and the polarization properties of the optical fiber sensor can result in the variation of the visibility and signal fading. Polarization scrambling is an important method to eliminate the input-polarization-induced fading. In this paper, the principles of the polarization scrambling are introduced. The influences of the perturbation to the input fiber and interferometer on the visibility are analyzed in two cases and the visibility properties in an interferometric optical fiber sensor are theoretically and experimentally demonstrated.

90-degree docking error control in polarization maintaining fiber resonator based on white-light interferometry

Polarization fluctuation caused by polarization coupling in polarization maintaining fiber (PMF) resonator is one of the major noise sources in resonant fiber optic gyroscope. Polarization axis 90-degree docking is an effective way to overcome the polarization fluctuation, but the 90-degree docking error has a major affect to the gyroscope noise suppression effect. In this paper, a fiber Michelson interferometer testing system of polarization coupling in doublecoupler polarization maintaining fiber resonator based on white-light interferometer is designed to realize 90-degree docking error control and obtain a good result of 0.37 degree experimental docking error. Then the detection method of sawtooth scanning is used to analyze the resonance characteristics and polarization characteristics of double-coupler polarization maintaining fiber resonator experimentally and obtains the response curve with 24 finesse and 179.65 degree phase interval of the two polarization eigenstates.