Active optical lattice filters

A method of optical signal processing, the method comprising the steps of:

• amplifying an optical signal in a first gain block and amplifying said optical signal in a second gain block, wherein said first gain block is coupled in cascade to said second gain block, said coupling providing partial reflection and partial transmission of said optical signal between said gain blocks;
• controlling a first gain associated with said first gain block and controlling a second gain associated with said second gain block, wherein said controlling is performed by applying a first control signal and a second control signal;
• and
• transmitting at least one output signal comprising partial transmission signals from said first gain block and said second gain block, wherein said gains are controllably set to cause said optical signal processing to be governed by a first transfer function which causes said output signal to comprise a first line frequency component, and at a later time in response to a switching control signal, to controllably set said gains to cause said optical signal processing to be governed by a second transfer function which causes said output signal to comprise a second line frequency component.

An optical signal processor comprising:

• a first gain block and a second gain block, wherein said first gain block is coupled in cascade to said second gain block, said coupling providing partial reflection and partial transmission of an optical signal between said gain blocks;
• a first controllable gain associated with said first gain block and second controllable gain associated with said second gain block, wherein said first and second controllable gains have values which force said optical signal processor to operate in an unstable region and thereby produce an oscillation so that an output signal comprises a tunable line frequency;
• and
• an output coupling transmitting an output signal comprising partial transmission signals from said first gain block and said second gain block, wherein said optical signal processor is a wavelength division multiplexer using said tunable line frequency as an optical carrier which is modulated onto an information sequence.