Fiber-based two-wavelength heterodyne laser interferometer

Abstract

Displacement measuring interferometry is a crucial component in metrology applications. In this paper, we propose a fiber-based two-wavelength heterodyne interferometer as a compact and highly sensitive displacement sensor that can be used in inertial sensing applications. In the proposed design, two individual heterodyne interferometers are constructed using two different wavelengths, 1064 nm and 1055 nm; one of which measures the target displacement and the other monitors the common-mode noise in the fiber system. A narrow-bandwidth spectral filter separates the beam paths of the two interferometers, which are highly common and provide a high rejection ratio to the environmental noise. The preliminary test shows a sensitivity floor of 7.5 pm / Hz at 1 Hz when tested in an enclosed chamber. We also investigated the effects of periodic errors due to imperfect spectral separation on the displacement measurement and propose algorithms to mitigate these effects.

Gyro-Free Inertial Navigation Systems Based on Linear Opto-Mechanical Accelerometers

“…Opto-mechanical accelerometers [19,20,23] are fused silica mechanical resonators, where a test mass is held by two 100 µm thick parallel leaf strips. Accelerations induce motions on the test mass, which are measured using heterodyne interferometry [24,25] or fiber-based optical cavities [26,27]. Below the natural angular frequency of the mechanical resonator, ω 0 , acceleration, and displacement are linearly related as x(t) = ω −2 0 ẍ(t).…”

A Compact and High-Precision Three-Degree-of-Freedom Grating Encoder Based on a Quadrangular Frustum Pyramid Prism

“…However, the laser interferometer is limited by the laser wavelength, which is the measurement standard [15,16]; therefore, in actual use, the wavelength is easily affected by the temperature and humidity in the environment, thus affecting accuracy [17][18][19]. Laser interferometers are generally used for measurements in a controlled environment in the laboratory, which can achieve high accuracy and stability [20][21][22]. The measurement standard of the grating encoder is the grating pitch [23,24].…”

Long binary coding design for absolute positioning using genetic algorithm

“…Optical methods include laser interferometers and grating interferometers, both capable of high measurement accuracy, albeit with certain limitations in their applications. On the one hand, laser interferometers excel in controlled environments like laboratories, where the laser wavelength remains stable and measurement accuracy is exceptionally high [6][7][8][9][10][11][12]. On the other hand, grating interferometers are preferred in scenarios where environmental conditions cannot be precisely controlled [13][14][15][16].…”