Wavelength selective mode couplers
AssigneeAT&T Bell Laboratories
InventorCraig D. Poole
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Abstract
A mode coupler is disclosed which utilizes a circularly symmetric perturbation in an electromagnetic waveguide. Due to the circular symmetry of the perturbation, exact cross-sectional alignment of the perturbations is not needed when several of the devices are cascaded. Further, the mode coupling response is wavelength dependent, and therefore, may be employed in electromagnetic filtering applications.
Claims8
A wavelength selective mode coupler for optical energy, the optical energy being comprised of low frequencies below a first predetermined value, high frequencies above a second predetermined value, and midrange frequencies between the first and the second predetermined values, the mode coupler comprising:
- a waveguide capable of supporting at least a first mode and a second mode, the waveguide including:
- an input, for receiving optical energy in a first mode,
- a substantially circularly symmetric perturbation of a predetermined period, the period being such that energy at the low frequencies and at the high frequencies remains in the first mode, energy at a predetermined frequency of the midrange frequencies is substantially coupled entirely from the first mode to the second mode, and energy at the midrange frequencies and not at the predetermined frequency is coupled to the second mode by an amount which varies with frequency.
A method of coupling optical energy in a first mode from the first mode to a second mode the method comprising the steps of:
- (a) injecting the optical energy in the first mode into a waveguide;
- (b) passing the optical energy through a substantially circularly symmetric perturbation in the waveguide, for coupling selected wavelengths of the optical energy from the first mode to a second mode and maintaining wavelengths not selected in the first mode, and
- (c) outputting the optical energy obtained in step (b) from the waveguide.
Dependencies are inferred from the claim text.