Research
Broad-bandwidth, long-haul, underwater fiber-optic sensing system
Underwater applications of distributed fiber-optic sensors comprise seismic sensing, earthquakes and tsunami monitoring and early warning, pipeline defense and leak detection, harbor security, monitoring the sounds used by marine animals for navigation and communication and more.
The technology that is being developed in our lab allows achieving simultaneously both very high sensitivity and very long range of operation. This is achieved by working with sensing fibers that comprise arrays of weak mirrors in their core and a pulse sequence which is accurately tailored to the sensing fiber. The careful design of the pulse sequence ensures that the returns from the fiber will not overlap even when the sampling rate increases by a factor of more than 50. Poster
A fiber-optic implementation
use sound and ultrasound for navigation and communication
Under water communication experimental setup with ten mandrels serving as a distributed receiver.
A fiber-optic implementation
Single-core optical fiber shape sensing and imaging
Optical fibers are used nowadays in many fields including structural health monitoring and medicine for purposes of shape sensing and imaging. In our research, we study methods for using a single-core optical fiber as an endoscope that can deliver shape information as well as images of the inspected object. For this purpose we mostly use speckle patterns acquired either at the proximal facet or at the distal facet of the fiber, and analyze them using deep learning algorithms. Poster
A multi-mode optical fiber (orange) is held on three mechanical stages for shape sensing experiment
A multi-mode optical fiber (orange) is held on three mechanical stages for shape sensing experiment
Pulse compression comparison in Q-DAS system: Ternary codes vs. Binary codes
Pulse compression techniques became popular in the last decade in many optical fields such as Laser Range Finders (LRF), Quasi and fully Distributed Acoustic Sensing (Q-DAS and DAS), Brillouin Sensing and more. In general, it allows increasing the transmitted energy while keeping the spatial resolution the same as that of a single pulse. A promising approach for implementing pulse compression is via Perfect Periodic Autocorrelation codes (PPA). Ideally, the autocorrelation of PPA codes is a sequence delta functions. This is a manifestation of the codes ability to achieve perfect compression. Therefore, replacing each transmitted pulse by a PPA code and compressing the received returns, leads to a significant improvement in the SNR. Out of the binary PPA codes, i.e. codes whose basic elements (bits) are two complex numbers, the largest families are the M-sequence and the Legendre code. Poster Abstract
