This simulator places two opposing ceramic ferrules on a micrometer stage. Change lateral core offset, axis angle, interface condition, air gap, mode radius, wavelength and contamination, and see the overlap of the two guided modes, the transmitted power from a 1 mW input and the insertion loss.
• A 3D scene with a fixed ferrule and fiber core, a micrometer alignment carriage, a mode-overlap interface, an end-face contamination patch, a first-facet return path and a coupled-power monitor. • Nine controls for lateral offset, angle, interface condition, air gap, mode radius, wavelength, obscured fraction, offset sweep and markers. • Ten readouts: current offset, lateral, angular and gap overlaps, two-interface transmission, combined coupling, insertion loss, power from 1 mW, first-facet reflected power and air Rayleigh range. • Four guided experiments, a verification bench, Curves & measurements and a Learn & assess tab.
With identical Gaussian modes of radius w, lateral offset d gives ηlateral = exp[−(d/w)²], so an offset of one mode radius couples e⁻¹ = 36.79% and costs 4.343 dB. Angle contributes ηangular = exp[−(π n w sinθ/λ)²] and an air gap contributes ηgap = 1/[1 + (g / 2zR)²] with zR = πw²/λ. An incoherent air gap also adds two Fresnel interfaces, each reflecting [(1.468 − 1)/(1.468 + 1)]² ≈ 3.6%.
The combined coupling is the product of the factors times one minus the obscured fraction, and insertion loss is −10 log10 of it. Loss from dirt and from misalignment are separate: an assigned 50% obscuration alone costs 3.0103 dB.
The model uses identical scalar Gaussian modes, a fixed glass index of 1.468 and a separated-factor approximation for combined misalignment. Matched contact ignores gap diffraction and reflection, the air-gap treatment is first-pass only with no coherent interference or multiple reflections, and uniform obscuration is a teaching approximation. The return readout is first-facet reflection only, and there is no connector certification or damage model.
The lateral overlap is exp(−1) = 36.79%, which is an insertion loss of 4.343 dB in the simulator. Loss grows with the square of offset before it is converted to decibels.
The beam diffracts across the gap, reducing mode overlap, and the glass-to-air and air-to-glass interfaces each reflect about 3.6% of the light. The simulator combines both effects.
No. Insertion loss is the power lost in transmission through the joint, while return loss describes power reflected back toward the source. The simulator reports the first-facet reflection separately.
As a uniform fraction of obscured power. It is a simple teaching approximation rather than a particle-scattering calculation, but it shows that contamination and misalignment are independent contributors.