Wide range optical wavelength fast detection for narrowband signal

A wavelength detection system comprising:

• one or more wavelength detection stages configured to receive at least a portion of an input light signal, wherein each wavelength detection stage comprises:
• a splitter to split a portion of the input light signal into two arms, wherein a free spectral range associated with the respective wavelength detection stage is associated with an optical path length difference between the two arms, wherein each of the one or more wavelength detection stages has a unique optical path length difference to provide a unique free spectral range;
• a 90-degree optical hybrid configured to accept light from the two arms, where the 90-degree optical hybrid provides two in-phase channel outputs and two quadrature channel outputs;
• and
• two differential detectors configured to generate an I-channel differential signal based on a difference between light from the two in-phase channel outputs and generate a Q-channel differential signal based on a difference between light from the two quadrature channel outputs, wherein a wavelength of the input light signal is linearly proportional to an arctangent of a ratio of the Q-channel and I-channel differential signals within the free spectral range of each of the one or more wavelength detection stages;
• and
• a logic device communicatively coupled to the two differential detectors of each wavelength detection stage, wherein the logic device is configured to:
• receive one or more sets of detection signals, wherein each of the one or more sets of detection signals includes an I-channel differential signal and a Q-channel differential signal from one of the one or more wavelength detection stages;
• and
• determining a wavelength of the input light signal based on an arctangent of a ratio of the Q-channel and I-channel differential signals for each of one or more sets of detection signals.