Measuring fiber optic wire vibration during manufacturing
Measuring fiber optic wire vibration during manufacturing
(OP)
What would be the best method to measure the vibration of a .007" fibre optic wire? The manufacturing process is likely causing the wire to vibrate and I want to measure the frequency that it is vibrating at, the phyical displacement of the vibration etc. Laser or strobe is about all I can come up with since it must be done without contact to the wire. I'll need to gather as much information on the wire as I can before I can decide how to proceed with determining the source and stopping the vibration. Let me know your ideas!
Thanks!
Thanks!





RE: Measuring fiber optic wire vibration during manufacturing
RE: Measuring fiber optic wire vibration during manufacturing
RE: Measuring fiber optic wire vibration during manufacturing
To answer your 2nd question, higher tension will cause higher frequency of vibration. An example of this is how a guitar or piano is tuned. The fundamental frequencies of a vibrating string is given by:
fn = Kn/(2*Pi)*sqrt((T*g)/(w*L^2)), where
fn = Natural frequency (hz)
Kn = Pi, 2*Pi, 3*Pi, etc.
T = String tension (lbf)
g = 386 lbm*in/lbf/s^2
w = Weight of string (lbm/in)
L = Length of strin (in)
This is assuming small displacements and zero bending stiffness of the fiber. For large displacements, the tension will fluctuate with displacement and cause a nonlinear stiffness increase.
RE: Measuring fiber optic wire vibration during manufacturing
RE: Measuring fiber optic wire vibration during manufacturing
Thanks again!
RE: Measuring fiber optic wire vibration during manufacturing
fn = Kn/(2*Pi)*sqrt((T*g)/(w*L^2)), where
fn = Natural frequency (hz)
Kn = Pi, 2*Pi, 3*Pi, etc.
T = String tension (lbf)
g = 386 lbm*in/lbf/s^2
w = Weight of string (lbm/in)
L = Length of strin (in)
RE: Measuring fiber optic wire vibration during manufacturing
RE: Measuring fiber optic wire vibration during manufacturing
Is it totally impossible to send a laser signal down the length of the fiber? Is the free end of the fiber accessible (even there's a mile of fiber between it and the vibration source)? Maybe there is a sharp enough impedance change at the point of extrusion to bounce a laser off of it. I ask because I have a friend at MIT who's doing part of his PhD work on phase smearing due to acoustical waves inside installed fiber optics. He would know.
Barring that, maybe a good question to ask would be: where exactly does the vibration input matter? If the problem is occurring at the point of extrusion and goofing up the cross-sectional integrity, then maybe measuring equipment displacement would be a good proxy for displacement in the fiber.
Also, have you considered modeling any parts of the system? Depending on where the vibration input is occurring, maybe a bit of finite element work on the equipment design would give you some direction on what to look for.
Byron
J. Byron Davis
Vibro-Acoustic Consultants
byron@va-consult.com
RE: Measuring fiber optic wire vibration during manufacturing