Optical device producing an intensity dependent phase shift
AssigneeBritish Telecommunications public limited company
InventorNicholas J. Doran
Life of this patent
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Abstract
An optical device comprises an optical waveguide (2) formed from at least a first material having a non-linear refractive index n.sub.2 coupled to a first pair of ports (4,5) of an optical coupler (3). An optical signal input at one of the second pair of ports (6,7) of the coupler (3) is split to provide two signals counter propagating around the waveguide loop (2). By selecting the coupling ratio and appropriate waveguide parameters to ensure an asymmetry in the device it is possible to produce an intensity dependent relative phase shift between the counter propagating signals, thereby to vary the device output. Embodiments of the invention may be used to perform logic functions on, to amplify, switch or otherwise modify an input signal.
Claims14
An optical device comprising a coupling means having first and second pairs of optical communication ports, in which portions of an optical signal received at a port of one pair are coupled into each port of the other pair in a predetermined coupling ratio;
- and an optical waveguide including a first material having a non-linear refractive index, and a second material in series with the first material, the first and second materials having non-commuting effects on an optical signal at a working intensity travelling along the waveguide, the optical waveguide coupling together the first pair of ports;
- the coupling ratio and appropriate waveguide parameters being selected such that in use the portions of an optical signal at a working intensity received at one of the second pair of ports of the coupling means, and coupled into each end of the waveguide, return to said coupling means with an intensity dependent relative phase shift after travelling around the waveguide.
A method of processing an optical signal comprising the steps of:
- providing an optical device having a coupling means having first and second pairs of optical communication ports, in which portions of an optical signal received at a port of one pair are coupled into each port of the other pair in a predetermined coupling ratio;
- and an optical waveguide at least a portion of which includes a first material having a non-linear refractive index, and a second material in series with said first material, the first and second materials having non-commuting effects on an optical signal at a working intensity travelling along the waveguide the optical waveguide coupling together the first pair of ports;
- the coupling ratio and appropriate waveguide parameters being selected such that in use the portions of an optical signal at a working intensity received at one of the second pair of ports of the coupling means, and coupled into each end of the waveguide, return to said coupling means with an intensity dependent relative phase shift after travelling around the waveguide;
- and
- inputting an optical signal into one of the second pair of ports of the device to produce two counter propagating signals within the waveguide, thereby to provide a processed pulse signal output at least at one of the second pair of ports.
An optical device comprising:
- a coupling means having first and second pairs of optical communication ports, in which portions of an optical signal received at a port of one pair are coupled into each port of the other pair in a predetermined coupling ratio;
- and
- an optical waveguide comprising material which supports soliton effects when optical pulses at appropriate working intensities are injected into the device, the length of the waveguide being sufficient such that the intensity dependent phase of an injected pulse is substantially uniform throughout the pulse after propagation through the waveguide, at least a portion of such waveguide including a first material having a non-linear refractive index, the optical waveguide coupling together the first pair of ports;
- the coupling ratio and appropriate waveguide parameters being selected such that in use the portions of an optical signal at a working intensity received at one of the second pair of ports of the coupling means and coupled into each end of the waveguide return with an intensity depending relative phase shift after travelling around the waveguide.
An optical amplifier including an optical device comprising:
- a coupling means having first and second pairs of optical communication ports, in which portions of an optical signal received at a port of one pair are coupled into each port of the other pair in a predetermined coupling ratio;
- and
- an optical waveguide at least a portion of which includes a first material having a non-linear refractive index, the optical waveguide coupling together the first pair of ports, the coupling ratio and appropriate waveguide parameters being selected such that in use the portions of an optical signal at a working intensity received at one of the second pair of ports of the coupling means and coupled into each end of the waveguide return with an intensity dependent relative phase shift after travelling around the waveguide;
- additional coupling means having a pair of input ports and an output port optically coupled with one of the second pair of ports of the one coupling means;
- and
- a bias signal source coupled with one of the input ports of the additional coupling means.
An optical logic gate including an optical device comprising:
- a coupling means having first and second pairs of optical communication ports, in which portions of an optical signal received at a port of one pair are coupled into each port of the other pair in a predetermined coupling ratio;
- and
- an optical waveguide at least a portion of which includes a first material having a non-linear refractive index, the optical waveguide coupling together the first pair of ports;
- the coupling ratio and appropriate waveguide parameters being selected such that in use the portions of an optical signal at a working intensity received at one of the second pair of ports of the coupling means and coupled into each end of the waveguide return with an intensity dependent relative phase after travelling around the waveguide.
Dependencies are inferred from the claim text.