Fiberooptic Laser Doppler Velocimeter

In summary, the conversation discusses a Laser Dopler velocimeter (LDV) system, which uses a light source (laser) and a flow seeded with particles to measure particle velocity. The system includes a directional 3DB coupler that allows light to pass through it, scattering on particles in the flow and then returning to the detector. The detector uses the Doppler-effect to determine the particle velocity. The conversation also raises questions about how the light is divided after passing through the 3DB coupler and when it returns from the fiber after scattering.
  • #1
Zokisa
1
0
Hi,

I have problem understanding some things about this particular LDV system(a Laser Dopler velocimeter).

google.jpg

Source is a light source - laser. On the right there is a flow seeded with particles that scatters the light.

So here we have a simple directional 3DB coupler. Light goes thought it, part of light goes thought the all fiber's length and on the distant end it comes out, scatters on a particle inside the flow and then it goes back to the fiber, comes thought the coupler and then reaches the detector. Detector determines particle velocity thought difference of frequencies of the light because of the Doppler-effect in the process of scattering.

Providing this is a 3 db counter, how is the light divided after passing thought it?
When the light comes back from the fiber after the scattering(in different direction than the laser light) how is it divided?

I hope somebody learned in school about such LDV's.
 
Last edited:
Science news on Phys.org
  • #2
Your picture link appears to be broken. At least to me.
 

What is a Fiberoptic Laser Doppler Velocimeter?

A Fiberoptic Laser Doppler Velocimeter (FLDV) is a scientific instrument used to measure the velocity of moving objects or fluids. It uses the Doppler effect, which is a change in frequency of light waves when reflected off a moving object, to determine the velocity of the object.

How does a Fiberoptic Laser Doppler Velocimeter work?

The FLDV consists of a laser, a fiberoptic probe, and a detector. The laser emits a beam of light that is split into two beams by a beam splitter. One beam is sent through the fiberoptic probe and directed towards the moving object, while the other beam is directed towards a stationary reference surface. The beams are then reflected back and combined, producing an interference pattern. The detector measures the changes in this pattern, which are used to calculate the velocity of the object.

What are the advantages of using a Fiberoptic Laser Doppler Velocimeter?

One advantage of using an FLDV is that it is a non-intrusive measurement technique, meaning it does not physically interfere with the object being measured. This makes it ideal for measuring delicate or complex objects. Additionally, FLDVs have a high accuracy and can measure velocities in a wide range of fluids, including opaque and highly turbid fluids.

What are some common applications of Fiberoptic Laser Doppler Velocimeters?

FLDVs have a wide range of applications in various fields, including fluid mechanics, aerodynamics, bioengineering, and environmental science. They are commonly used to study and analyze the flow of fluids in pipes, rivers, and oceans, as well as the movement of particles in suspensions.

Are there any limitations to using Fiberoptic Laser Doppler Velocimeters?

One limitation of FLDVs is that they require a clear line of sight between the probe and the moving object, which may be difficult to achieve in certain applications. Additionally, FLDVs are sensitive to environmental factors such as vibrations and temperature changes, which can affect the accuracy of the measurements. Proper calibration and maintenance are necessary to ensure reliable results.

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