Photonic waveguide power and phase monitor

A method for optical monitoring, the method comprising:

• receiving, from a first optical signal propagating in a first waveguide, a portion of the first optical signal coupled from the first waveguide into a first input of an optical monitoring device;
• receiving, from a second optical signal, at least a portion of the second optical signal coupled into the second input of the optical monitoring device;
• controlling, by a mixing unit, combining of the portion of the first optical signal with the at least a portion of the second optical signal into at least one combined signal at at least one output from the mixing unit;
• applying a modulation signal in the mixing unit so as to modulate, after the portion of the first optical signal having been coupled from the first waveguide into the first input, at least one of a phase of the portion of the first optical signal, or an amplitude of the portion of the first optical signal being transferred into one of the at least one combined signal, and/or to modulate, after the at least a portion of the second optical signal having been coupled into the second input, at least one of a phase of the at least a portion of the second optical signal, or an amplitude of the at least a portion of the second optical signal being transferred into one of the at least one combined signal;
• and
• detecting, by at least one photodetector, the at least one combined signal by generating an electric signal dependent on an amplitude of the at least one combined signal incident onto the at least one photodetector.

An optical monitoring device comprising:

• a first input configured to receive a portion of a first optical signal coupled from a first waveguide into the first input;
• a second input configured to receive at least a portion of a second optical signal coupled into the second input;
• a mixing unit configured to control combining of the portion of the first optical signal with the at least a portion of the second optical signal into at least one combined signal at at least one output from the mixing unit;
• at least one photodetector configured to detect the at least one combined signal by generating an electric signal dependent on an amplitude of the at least one combined signal incident onto the at least one photodetector,
• wherein the optical monitoring device is further configured to apply a modulation signal so as to modulate at least one of a phase of the portion of the first optical signal, a coupling of the portion of the first optical signal into the first input, or an amplitude of the portion of the first optical signal being transferred into one of the at least one combined signal, and/or to modulate at least one of a phase of the at least a portion of the second optical signal, a coupling of the at least a portion of the second optical signal into the second input, or an amplitude of the at least a portion of the second optical signal being transferred into one of the at least one combined signal;
• and
• a dynamic coupling element configured to tunably couple the portion of the first optical signal from the first waveguide such that an amplitude of the portion of the first optical signal, coupled from the first waveguide, is controllable,
• wherein the optical monitoring device is further configured to apply a modulation signal to the dynamic coupling element so as to modulate the coupling of the portion of the first optical signal in response to the modulation signal.