High speed optical analog to digital converter and digital optical wavemeter

A method of analogue to digital (A/D) conversion, comprising the steps of;

• frequency modulating an optical signal with an Input analogue voltage signal,
• splitting the frequency modulated optical signal and generating at least one differentially delayed optical signal and at least one reference signal,
• combining the or each of the delayed optical signal with the or one of the reference signal(s) to generate a combined signal or signals, and converting the or each combined signal into a digital signal.

A digital optical wavemeter for generating a digital representation of the frequency of an input optical signal, comprising:

• delay means for splitting the input optical signal and generating at least one differentially delayed optical signal and at least one reference signal,
• at least one combining means arranged to combine the or each delayed optical signal with the or one of the reference signal(s), and
• at least one converter means for converting a combined signal output from an associated one of the combining means to digital output.

A method for generating a digital representation of the wavelength of an input optical signal, comprising the steps of:

• splitting the input optical signal and generating at least one differentially delayed signal and at least one reference signal,
• combining the or each of the differentially delayed signal with the or one of the reference signal(s) to generate at least one combined signal, and
• converting the or each combined signal into a digital signal.