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single mode setting…

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(joined April 2014)
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In opti bpm which setting is considered better or almost definition of the setting to how to recognize the wave guide as single mode or multi-mode? is it reliable? (scalar?, complex or real?, number of mode?)

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    • #14583

      In opti bpm which setting is considered better or almost definition of the setting to how to recognize the wave guide as single mode or multi-mode? is it reliable? (scalar?, complex or real?, number of mode?)

    • #14607
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      Damian Marek
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      The Mode solver can be very reliable! Remember though sometimes the user may need to make some changes to the simulator to give a more accurate result much quicker.

      Scalar mode solvers will approximate that the two transverse components are independent and thus will find less modes. For example in a optical fiber a scalar mode solver will calculate the LP modes but not the EH and HE modes that constitute the LP modes. These will be calculated by a vector method. Generally if polarization effects are important you should use a vector method.

      Whether a complex or real option is chosen will determine whether the mode solver will calculate a complex propagation constant which includes modal loss information.

      Since a mode solver generally just solves an eigenvalue equation, it is hard for it to know the number modes that a waveguide should support. This option will tell the solver to assume that waveguide will have x number of modes and try to solve for all of them.

      Regards

      +2
    • #14836

      still I have problem that some times if I choose real in setting I will get single mode other side if I choose the complex I will get at least 2 modes, which one I have to go for? I am not using scalar this time, just follow the defaults but changing the real and complex and I saw the modes will be changed, I need single mode, do I have to change my design and recheck it again in both sides? I mean real and complex should be single mode both?

      • #14870
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        Damian Marek
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        You should be fine with using the real solver. The complex solver would be useful if you materials were defined as lossy materials with a complex index of refraction. If you use a complex solver with real materials the mode solver can find leaky modes, which you are not interested in.

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