Apparatuses and methods for optical code-delay reflectometry (OcoDR)

An apparatus, comprising:

• a receiver configured to:
• generate interfered electromagnetic (EM) radiation responsive to reference EM radiation and reflected EM radiation, the reflected EM radiation received from a system under test responsive to modulated EM radiation provided to the system under test, the reference EM radiation and the modulated EM radiation including continuous-wave EM radiation;
• and
• generate a continuous interferogram responsive to the interfered EM radiation;
• and
• control circuitry configured to:
• provide a sequence to a modulation signal source to generate the modulated EM radiation responsive to incident EM radiation;
• digitize the continuous interferogram to obtain a digitized continuous interferogram;
• and
• extract phasors corresponding to different delays responsive to applying one of the sequence or a complex conjugate of the sequence to the digitized continuous interferogram.

A method of performing Optical Code Delay Reflectometry (OCoDR), the method comprising:

• modulating a sequence on incident electromagnetic (EM) radiation to obtain modulated EM radiation, the sequence having at least substantially zero circular autocorrelation for non-zero shifts of the sequence;
• injecting the modulated EM radiation into a system under test;
• interfering reflected EM radiation received from the system under test responsive to the modulated EM radiation with reference EM radiation to obtain interfered EM radiation, the reference EM radiation including substantially fixed frequency continuous-wave EM radiation;
• converting the interfered EM radiation into an electrical signal;
• digitizing the electrical signal to obtain a digitized continuous interferogram;
• and
• applying one of the sequence or a complex conjugate of the sequence to the digitized continuous interferogram to obtain phasors corresponding to different delays.

A method of performing Optical Code Delay Reflectometry (OCoDR), the method comprising:

• modulating a Zadoff-Chu sequence on incident electromagnetic (EM) radiation to obtain modulated EM radiation, the incident EM radiation and the modulated EM radiation including continuous-wave EM radiation;
• injecting the modulated EM radiation into an optical fiber;
• interfering reflected EM radiation received from the optical fiber responsive to the modulated EM radiation with reference EM radiation to generate interfered EM radiation;
• converting the interfered EM radiation to an electronic signal comprising an interferogram;
• digitizing the electronic signal to generate a digitized interferogram;
• determining a complex conjugate of one of the Zadoff-Chu sequence or the digitized interferogram;
• multiplying the complex conjugate of the one of the Zadoff-Chu sequence or the digitized interferogram with the other of the Zadoff-Chu sequence or the digitized interferogram to generate a product;
• and
• determining a frequency-domain representation of the product to recover a vector of phasors.