# UltraFast Optical Imaging using Multimode Fiber based Compressed Sensing and Photonic Time Stretch

## TL;DR

This paper introduces an ultrafast optical imaging system using a single multimode fiber for all-optical random pattern generation combined with photonic time stretch, enabling high-speed compressive sensing imaging with low-cost components.

## Contribution

The work demonstrates a novel all-optical speckle pattern generation method using multimode fiber and photonic time stretch for ultrafast compressive sensing imaging.

## Key findings

- Achieved 27x27 pixel image reconstruction within 500 measurements.
- Analyzed FFT spatial resolution, achieving 50x50 pixels with 4 speckle patterns.
- Confirmed low correlation (0.074) of speckle patterns across wavelengths.

## Abstract

An ultrafast single-pixel optical 2D imaging system using a single multimode fiber (MF) is proposed. The MF acted as the all-optical random pattern generator. Light with different wavelengths pass through a single MF will generator all-optical random speckle patterns, which have a low correlation of 0.074 with 0.1nm wavelength step from 1518.0nm to 1567.9nm. The all-optical random speckle patterns are perfect for compressive sensing (CS) imaging with the advantage of low cost in comparison with the conventional expensive pseudorandom binary sequence (PRBS). Besides, with the employment of photonic time stretch (PTS), light of different wavelengths will go through a single capsuled MF in time serial within a short pulse time, which makes ultrafast single-pixel all-optical CS imaging possible. In our work, the all-optical random speckle patterns are analyzed and used to perform CS imaging in our proposed system and the results shows a single-pixel photo-detector can be employed in CS imaging system and a 27 by 27 pixels image is reconstructed within 500 measurements. In our proposed imaging system, the fast Fourier transform (FFT) spatial resolution, which is a combination of multiple Gaussians, is analyzed. Considering 4 optical speckle patterns, the FFT spatial resolution is 50 by 50 pixels. This resolution limit has been obtained by removing the central low frequency components and observing the significant spectral power along all the radial directions.

---
Source: https://tomesphere.com/paper/1803.03061