Meiyuan Wen

A multimode fiber sensor using the intensity inner product of speckle fields is presented. The sensitivity and the dynamic range of the displacement sensing are quantitatively analyzed. We show that the sensitivity of displacement can be in the submicrometer range. Experimental performances show that the results are consistent with the calculated results.

An optical interconnection architecture using a photo-refractive (PR) crystal with low power visible light tunable laser diode array is proposed.

Clinical imaging protocols designed to accelerate acquisition or reduce radiation dose often lead to degraded image quality, compromising diagnostic confidence. The heterogeneity in degradation types and severities across imaging modalities further challenges the development of generalized restoration solutions. In this work, we introduce a unified framework that formulates medical image restoration as posterior sampling from self-supervised Latent Diffusion Models (LDMs), pretrained on multi-modal high-quality images. At the core of our method is an Estimation Posterior Sampling (EPS) strategy, which enhances both data fidelity and anatomical detail retention. EPS incorporates two key components: (i) estimated diffusion initialization to constrain sampling within the measurement-consistent solution space, and (ii) gradient-balanced optimization to adaptively trade off denoising strength and detail preservation throughout the diffusion trajectory. Unlike traditional task-specific models, our approach enables Plug-and-Play (PnP) deployment, supporting diverse degradations without retraining. Extensive experiments conducted on deterministic degradations (e.g., under-sampled MRI, sparse-view CT) and blind degradations (e.g., low-dose PET) across multiple degradation levels demonstrate superior quantitative and qualitative performance compared to both supervised baselines and state-of-the-art posterior sampling methods. Notably, our method achieves PSNR improvements of up to +2.9 dB (MRI), +1.1 dB (CT), and +0.9 dB (PET) in PnP mode. These results highlight the robustness and broad applicability of our framework for clinical deployment.

It is well known that by perturbing a multimode fiber, a complicated speckle pattern can be observed in the far field. The speckle field is highly sensitive to the fiber status changes, and this sensitivity is caused by the surrounding sensing environment. The proposed technique is based on the fact that taking the intensity inner product of two speckle fields, for example, before and after the perturbation, represents the similarity between the two speckle patterns that is related to the external changes (such as strain or displacement). Preliminary analysis and experimental demonstrations are provided, in which we have shown that the sensitivity of the proposed multimode fiber sensor can be as high as 0.1 μm.