Fiber optic magneto-responsive sensor assembly

A method of passively monitoring a location of a downhole assembly moving through a well via casing collar detection, the method comprising:

• transmitting light over a fiber optic line to a poled monolithic structure of the assembly during the moving thereof through the well;
• utilizing a magneto-responsive sensor of the assembly to generate voltage as the assembly passes a casing collar at a known location in the well;
• obtaining the voltage at a first portion of the poled monolithic structure to increase a diameter thereof;
• obtaining the voltage at a second portion of the poled monolithic structure to decrease a diameter thereof;
• relaying light from each of the increased diameter and decreased diameter ends of the poled monolithic structure over the fiber optic line;
• and
• calculating a differential of the diameters to confirm casing collar detection by the assembly.

A casing collar locator assembly for traversing a well, the assembly comprising:

• a magneto-responsive sensor for detecting a casing collar at a wall of the well;
• a voltage responsive structure with first and second portions each coupled to the sensor for obtaining voltage therefrom upon the detecting of the casing collar, the obtaining of the voltage to dimensionally alter the portions;
• and
• an imbalanced multi-fiber optic line having a first fiber about the first portion of the device and a second fiber about a second portion of the device, the fibers about the portions of predetermined optically detectable different lengths from one another.

A method of passively monitoring a location of a downhole assembly moving through a well via casing collar detection, the method comprising:

• transmitting multiple wavelengths of light over an imbalanced multi-fiber optic line to a voltage responsive device of the assembly during the moving thereof through the well, the multi-fiber optic line including a first fiber about a first portion of the device and a second fiber about a second portion of the device that is of an optically detectable different length from the first fiber;
• utilizing a magneto-responsive sensor of the assembly to generate voltage as the assembly passes a casing collar at a known location in the well;
• obtaining the voltage at the voltage responsive device for dimensional altering thereof;
• utilizing an interferometer to return the multiple wavelengths of light, the multiple wavelengths affected by the dimensional altering of the voltage responsive device to confirm casing collar detection.