Resonance modes of optical fibers

  • 21 January 2023
  • 5 replies

Hello to Zemax community

In our last publication (, the aim was to detect micro-structures as the nuclei. Now, we interest us more specifically to the collagen fibers.

To start this study, the model given by the three equations of optics (supplementary 1 of the paper), is applied to classical step-index fibers (see a few results below).

Simulation of a few resonance modes of the 62.5/125 µm fiber with refractive index of the core nc=1.54, refractive index difference Δ=0.01 (a/ LP01,b/ LP11,c/ LP21,d/ LP02,e/ LP21,f/ LP22).

Do we can simulate these different resonance modes of fibers with OpenStudio? Thank you in advance to give us the procedure, if it exists.

Kind regards, Benoît.


Best answer by Jeff.Wilde 21 January 2023, 09:37

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You should be able to do this in OpticStudio using Physical Optics Propagation (POP) with an input beam defined either by a DLL (e.g., Laguerre-Gauss modes with a DLL that is provided with the software), or by LP modes that can be imported into OpticStudio as ZBF files.  For the DLL approach, this article may help:




Dear Jeff,

Thank you for your reply.

Best regards,


Hello everybody,

The “Physical Optics propagation” module can allowed compute the light propagation in optical fibers (see below two simulations).


However, the figure resolution is not very good (spot at end of fiber). Do you have a solve to improve it? Thank you in advance.

Kind regards, Benoît.

PS The simulation files are attached to this message.

Userlevel 6
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Hi Benoît,

POP is designed to model free-space propagation, not guided-wave propagation.  So, POP can simulate light that exits a multimode fiber (a discrete mode or combination of modes) and subsequently propagates through a free-space optical path.  It can also be used to calculate the coupling efficiency of a focused free-space beam into a specific mode of a multimode fiber.  By stepping through a set of modes, you can obtain the coupled mode power distribution inside the fiber at the launch point, which may be what you are looking to determine (although this distribution could change with subsequent propagation due to mode coupling).

For large-core multimode fibers (say 50 microns or greater), where the mode structure can be neglected, then ray tracing (not POP) can be used to model light propagation inside the fiber.  This is done using a non-sequential model for the fiber.

Alternative software exists for modeling guided-wave/fiber propagation, for example, OptiFiber (by Optiwave) or OptSim (by Synopsys).



Hello Jeff,

Thanks for your precious data. I began to study the products that you advise me:

First one, OptiFiber by Optiwave seems me build using the electromagnetic theory as Mie’s computations (TFDT). The break with the geometric aspect (Pieper (RJ.), Nassopoulos (A.), The Eikonal Ray Equations in Optical Fibers, IEEE Transactions on Education, 40(2) (1997)) is annoying to me. In particular, the mode LP01 shows light for radius equal than zero (see the figure below).

Perhaps, this result is due to the Gaussian beam which occupies the center of fiber (Gaussian aspect); I rather expected to observe a ring. It seems me not logical compared to the mode LP11 (see the reference above).

Second one, OptSim by Synopsys seems deduct directly to the Helmholtz equation and seems show only the transversal modes (because scalar field?).

I will better examine these two references, thank for your answer.

Kind regards, Benoît.