## 1 Introduction  
The Laser Doppler Vibrometer (LDV) holds an indispensable role in vibration detection due to its non-contact measurement approach and exceptionally high measurement resolution [1, 2]. The heterodyne interferometric measurement, based on the Mach-Zehnder configuration, is the predominant architecture for LDVs, widely adopted for its simple, stable design, and robust resistance to signal interference. Building upon this, fiber-optic interferometric LDVs have seen rapid development, benefiting from advantages such as easy alignment, superior stray light suppression, and high integration levels [3]. In traditional vibration measurement applications, the targets are typically non-cooperative. The speckle effect of the laser results in a returned wavefront that deviates from the ideal spherical shape, which can cause interference signal loss between the measurement and reference beams. Additionally, the target's vibration induces continuous changes in the speckle pattern, further increasing the likelihood of short-term signal loss. Traditional orthogonal demodulation algorithms can introduce spike noise, thereby decreasing the data reliability [4; 5]. Consequently, investigating the relationship between speckle behavior and coupling efficiency, along with the development of effective spike noise suppression methods, is crucial for improving the stability of LDV data acquisition and enhancing target adaptability. Considerable research has been conducted on the generation and suppression of spike noise. [PERSON] et al. developed a light field transmission model for the transmission and coupling processes in fiber-optic LDVs, providing an explanation for the origins of spike noise [6]. While the impact of transmitting-receiving lens f-number on speckle patterns was thoroughly analyzed, the wavelength-dependent effects remain unexamined in the current study. One optical method to mitigate spike noise is diversity reception. [PERSON] et al. proposed multi-aperture reception of the returning light signal, which reduced the probability of spike noise due to signal loss by a factor of 30 [7]. However, non-coaxial errors exist in vibration measurements across different sub-apertures. [PERSON] et al. examined the statistical distribution characteristics of the signals received by LDV detectors and suggested polarization diversity reception to enhance signal quality [8]. However, the polarization diversity reception scheme is susceptible to stray light interference, which can degrade the signal quality in one polarization channel. [PERSON] et al. introduced a multi-channel demodulation technique based on carrier power energy combination, significantly improving the stability of vibration measurements [9]. The algorithm computes weights based on random noise assumptions but fails to specify the methodology for real-time carrier amplitude acquisition. Additionally, [PERSON] applied the Kurtosis coefficient to identify spike noise in speech and employed adaptive filtering to smooth the spike components, greatly improving speech intelligibility [10]. However, this solution only compensates for missing data algorithmically and cannot enhance system performance at the hardware level. [PERSON] established a probabilistic model for dual-wavelength backscattered energy from rough targets, which suppresses spike noise but fails to account for the impact of limited transceiver aperture size on speckle noise [11]. This study simulates the laser transmission and reception processes, rough surface generation, and fiber coupling to examine the correlation of coupling energy under different wavelength conditions. The proposed dual-wavelength LDV leverages the distinct speckle characteristics of each wavelength, where the moments at which spike noise occurs in the interference signal do not completely coincide. By combining the amplitude envelopes derived from orthogonal demodulation with a weighted aggregation of dual-channel velocity data, the likelihood of spike noise occurrence is substantially reduced.