Shufen Chen

Properties of a fiber-transmission filter based on Bragg grating and its applications in ring-laser gyros

Wen JiShufen ChenLei FuZhengfeng ZouFanjun RaoBeijing Institute of TechnologySchool of Optoelectronics5 South Zhongguancun Street, Haidian DistrictBeijing 100081, ChinaE-mail: jiwen@bit.edu.cnAbstract. A fiber transmission filter is proposed and experimentallyexplored. The bandwidth of the filter is less than 0.1 nm, the loss andback-reflection index is 1.84 dB∕18.60 dB for one direction and1.57 dB∕20.78 dB for the other direction, figures which exhibit a greatvalue for ring-laser gyros. By utilizing this filter, a bidirectional laserwave carrying a beating signal can be obtained in a homogeneouslybroadened gain medium. Finally, a ring-laser gyro with its lock-in area lessthan 10 deg sec

Study of a high-precision SAW-MOEMS strain sensor with laser optics

A novel structure design of a surface acoustic wave (SAW) micro-optic-electro-mechanical-system (MOEMS) strain sensor with a light readout unit is presented in this paper. By measuring the polarization intensity ratio of the TE/TM mode outputted from the waveguide, the strain produced from an object can be measured precisely. The basic working principle of the SAW MOEMS strain sensor is introduced and the mathematical model of the strain sensor system is established. The SAW characteristics effected by the strain sensor are mathematically deduced. The coupling coefficient between the SAW modes and light modes can be calculated based on the theory of coupling modes. The conversion coefficient of polarized light modes is obtained. Due to the restrictions of the specific parameters of the device, the level of technology and the material characteristics, the sensitivity of the strain sensor system is calculated through simulation as 0.1 μe, with a dynamic range of 0 ~ ±50 μe.

Detecting surface acoustic wave gyroscopic signal by acousto-optic coupling

A technique for surface acoustic wave (SAW) gyroscopic signal detection by acousto-optic coupling is presented in this article. The principles of the technique and the detection structure were analyzed, and experiments were conducted using the gyroscope. The static results show that the maximum coupling efficiency obtained using this technique is 80.02% when the acousto-optic interaction length is maintained at 15 mm, the SAW electrical power is 99 mW, and the SAW frequency is 168.201 MHz. When the gyroscope was rotating, a linear voltage-rotation response curve was obtained and the sensitivity was approximately 1.2 mV/deg/s.

An erbium-doped fiber ring laser gyroscope with polarization splitting structure

A new type of fiber ring laser gyroscope with polarization splitting structure is presented. Bidirectional single-mode oscillations are generated inside the fiber cavity, and a rotation-sensitive beat signal is obtained which indicats that the beat frequency shift is linear to rotation rate.

45° coupling loss for non-round fiber core in the Lyot fiber depolarizer

There is a coupling loss at the joint of the Lyot depolarizer consisting of two sections of birefringent fiber (Polarization Maintaining fiber or PM fiber) with non-round fiber core. The contribution to the loss for the non-roundness of the fiber core was calculated and analyzed using a method based on second moment. And the result obtained is in agreement with the experiment and so demonstrates the exist of the loss. This also provides a method of analyzing and calculating the coupling loss for non-round fiber core in the paper and is useful for manufacturing the Lyot fiber depolarizer and researching on the stability of the depolarizer type of a single mode interference fiber optic gyro (IFOG).