Application Cases

Experimental Name: Resonant Characteristic Testing of Adaptive Fiber Optic Collimator (AFOC)

Test Equipment: High-voltage amplifier, laser, position-sensitive detector, signal generator, computer, etc.

Figure 1: Schematic diagram of the resonant characteristic testing scheme for the Adaptive Fiber Optic Collimator

Experimental Process:

Figure 1 shows the schematic diagram of the resonant characteristic testing scheme for the AFOC. The tail fiber of the laser is connected to the built-in fiber of the AFOC. The collimated laser beam from the AFOC is focused onto the photosensitive surface of the position-sensitive detector (PSD) via a focusing lens. A sinusoidal frequency-swept electrical signal generated by the PC is applied to the AFOC after being processed by the high-voltage amplifier. This signal controls a pair of dual piezoelectric drivers in the X-direction to move the fiber end face along the X-direction, ultimately causing the focused spot to shift in the corresponding direction on the PSD. The PSD transmits the detected shift amount *d* of the focused spot to the computer. The relationship between the sweep frequency and the displacement Δ*x* of the fiber end face can be obtained through calculation.

Experimental Results:

Figure 2: Comparison of resonant characteristic curves of the Adaptive Fiber Optic Collimator before and after vibration damping

Using the test setup shown in Figure 1, the resonant characteristics of the developed AFOC were tested both without and with the added vibration damping structure. As can be seen from Figure 2, the resonant frequency of the AFOC without the vibration damping structure is around 1.68 kHz. After adding the vibration damping structure, the first-order resonant frequency of the AFOC increases to 1.88 kHz, and the resonant peak is reduced by approximately half, indicating that the resonant peak is suppressed while the resonant frequency is increased.

Figure 3: (a) Comparison of frequency characteristics between the AFOC and the biquad filter; (b) Comparison of the frequency characteristics of the AFOC before and after filtering

Comparing the frequency characteristic curve of the transfer function of the biquad digital filter and the resonant characteristic curve of the AFOC before filtering in Figure 3(a), it can be seen that the notch frequency of the biquad digital filter equals the peak frequency of the AFOC, and the frequency corresponding to the normalized magnitude of approximately 1 equals the corresponding frequency of the AFOC, with opposite trends in magnitude variation, proving that they satisfy the complementary relationship derived from the theory. The actual frequency characteristic curve of the AFOC after filtering measured by the test setup shown in Figure 1 is shown in Figure 3(b). The experimental filtering results basically match the theoretical filtering results, verifying the correctness of the theoretically established model. Comparing the measured frequency characteristic curves of the AFOC before and after filtering, it can be seen that after filtering by the biquad transfer function, the first-order resonant peak of the AFOC is basically canceled out, resulting in an approximately flat frequency characteristic curve. The effective bandwidth within the 3dB attenuation range reaches 2.5 kHz, proving the feasibility of using the biquad digital filtering method to filter the control signal and improve the control bandwidth.

High-Voltage Amplifier Recommendation: ATA-7030 High-Voltage Amplifier

Figure: ATA-7030 High-Voltage Amplifier Specifications and Parameters

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