Dielectric waveguides
AssigneeThe Post Office
InventorJohn Edwin Midwinter
Life of this patent
Estimating the term…
Abstract
The number of modes propagating as guided modes along a dielectric optical waveguide depends on the refractive index difference between core and cladding materials. By altering this difference the number of modes which are permitted to propagate may be controlled. The effective bandwidth of a dielectric optical waveguide depends on the number of modes transmitted because of group delay dispersion and hence this bandwidth may be controlled by controlling the number of propagating modes. In the case of a liquid cored dielectric optical waveguide, the difference between core and cladding refractive indices and hence the bandwidth may be controlled by controlling the temperature of the dielectric optical waveguide.
Claims7
A mode limiter for use in an optical communications system in which signals are modulated on to a light beam transmitted over a multi-mode dielectric optical waveguide, including more trimmer means, through which said light beam can propagate in only a limited number of modes, to a detector, said signals having a bandwidth after detection determined by said number of modes, said mode limiter comprising:
- mode trimmer means including a section of liquid cored dielectric optical waveguide whose temperature determines said number of modes;
- control means for varying the temperature of said guide to vary the number of modes propagating through said trimmer means in response to an error signal;
- an optical detector for extracting said signals from said light beam after said light beam has propagated through said mode eliminator means;
- bandwidth measuring means connected to said optical detector for producing an output representative of said bandwidth;
- and
- comparator means connected to said bandwidth measuring means for producing said error signal when said bandwidth deviates from a predetermined bandwidth.
Dependencies are inferred from the claim text.