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You don’t need to observe the field pattern to determine if it is a cladding mode. There is another way to identify cladding modes. They are the ones whose modal index is smaller than the refractive index of the cladding layer. When the modal index is smaller than the cladding index, the mode number in the radial direction is a real number. Then the wavefunction follows harmonic Bessel functions and not exponential ones. That is why the field can persist to the cladding boundary. The modal field propagates out to the cladding boundary and it makes it a cladding mode.