Discussion Forum

Hi

basically you must first analyis and identify which elements of the stress analysis is influencing the light propagation (probably the stress but how, and what else?), and then which parameter of the light interacts with the structure (perhaps intensity and absorption through temperature ?) etc.

Then, you must plug these vaiables or derivation from these variables into the respective other applications.

Read through the documentation again and search the model gallery, there are different examples of coupling physics, if you cannot find it readily made up in one of the prepared Comsol application modes

Good luck
Ivar

Ivar,

thanks for giving your reply,

Actually my structure is step index single mode fiber, i can apply force on the fiber, by that there is change in the fiber structure (i.e fiber length) corresponding there is a change in the refractive index of the fiber and after change in the intensity.

I have certain relations based on that i can measure, How can i edit these equations for my model.
For my analysis relations are 1) force and fiber length
2) force and intensity variations
3) force and refractive index
if you know please help me.


Nagamalli

Hi

At least we can try to get some steps further.

Here would be my way to consider this, with what I understand so far:

I know (whithout having the references to say how and how much with me just now, but there are also many refereces on the web) that when you apply stress on glass or most glassy-type materials you will have an index of refraction change. I assume you have an amorphe glass so we can forget about an optical index tensor, at least to begin with, crystalline material would typically have a index of refraction tensor defined with respects to the crystalline coordinate system.

This means that for the optical application mode we must state that the index is something like

n = n0 + nstree*mises_WhateverStructuralApplicationModeName

You might also add a temperature dependance on the index if required and known f the type +n_temp*(T-T_opticalReference), with T_opticalReference being your reference temperature w.r.t. which the n_temp is defined.

Then, when you apply a force on the fibre, through the Young modulus you can calculate the fibre elongation. A longer fibre means more material with high index hence hence phase change if you use the fibre in an interferometer. This is treated/solved in the structural application mode and does not need any further specificities.

One thing though, usually we solve for the pressure p [Pa=N/m^2], which is defied as Force over Area, so if we know the force, we must apply it to an area (or an edge in 2D with a given depth, hence still an area) to get the units OK.

Finally, we need to select in which order to solve the problem. I beleive from this there is no direct implication from the light intensity on the structure (i.e. no heat generation from the optical power) then I would start by solving for the structural case alone, hence calculating size changes and stress changes in the fibre, then save the model, and then run the optical analysis from the saved solution to use the deformations and stress levels as base for the optical analysis. This you can select in the Solver Manager manually, or use the segregated solver sequenceer in the Solver Settings menu

I hope this helps, good luck
Ivar

thank you Ivar