Complete characterization of polarization-maintaining fibers using distributed polarization analysis
View Patent ↗Devices, systems and techniques for measuring optical polarization-related parameters in optical materials and devices such as polarization maintaining (PM) fiber links based on polarization crosstalks that spatially distribute over a length of a material such as a PM fiber link.
1. A method for measuring polarization-related parameters in a birefringent material; comprising:
engaging a fixture having a spatially periodic structure to a birefringent material along a length-wise direction of the birefringent material to cause polarization crosstalk peaks at different stressed and periodic spatial locations having a known spacing between two adjacent stressed and periodic spatial locations as defined by the spatially periodic structure where each crosstalk peak is generated by coupling light in one optical polarization supported by the birefringent material into another different optical polarization supported by the birefringent material at each stressed spatial location;
directing probe light into the birefringent material having the stressed and periodic spatial locations to cause coupling between different optical polarizations supported by the birefringent material;
detecting the probe light coming out of the birefringent material to determine spatial positions and spatial widths of the induced polarization crosstalk peaks; and
using the determined spatial positions and spatial widths of the induced polarization crosstalk peaks to extract one or more polarization-related parameters of the birefringent material including a birefringence thermal coefficient that is measured based on both (1) a shift in spatial position of one of the polarization crosstalk peaks and (2) the known spacing between two adjacent stressed and periodic spatial locations as defined by the spatially periodic structure.
2. The method as in claim 1 , wherein the one or more polarization-related parameters of the birefringent material include birefringence (or a beat length) of the birefringent material.
3. The method as in claim 1 , wherein the one or more polarization-related parameters of the birefringent material include a spatial birefringence variation along the birefringent material.
4. The method as in claim 1 , wherein the one or more polarization-related parameters of the birefringent material include birefringence dispersion of the birefringent material.
5. The method as in claim 1 , wherein the one or more polarization-related parameters of the birefringent material include a birefringence temperature coefficient of the birefringent material.
6. The method as in claim 1 , wherein the one or more polarization-related parameters of the birefringent material include birefringence (or a beat length) of the birefringent material, a spatial birefringence variation along the birefringent material, or birefringence dispersion of the birefringent material.
7. The method as in claim 1 , wherein the determined spatial positions and spatial widths of the induced polarization crosstalk peaks are used to extract a collection of polarization-related parameters of the birefringent material,
wherein the collection includes birefringence (or a beat length) of the birefringent material, a spatial birefringence variation along the birefringent material, birefringence dispersion of the birefringent material, and a birefringence temperature coefficient of the birefringent material.
8. The method as in claim 1 , wherein the birefringent material is a polarization maintaining fiber link.
9. A device for measuring distribution of polarization coupling in a length of polarization maintain (PM) fiber, comprising:
a structure engaged to a length of PM fiber and having a spatially periodic structure with a known spatial period to cause a series of polarization crosstalk peaks along the length of PM fiber at different stressed and periodic spatial locations where each crosstalk peak is generated by coupling light in one optical polarization mode supported by the PM fiber into another orthogonal optical polarization mode supported by the PM fiber at each stressed spatial location;
a mechanism that couples a linearly polarized light of a broadband spectrum into the length of PM fiber;
an optical delay device located downstream from the PM fiber in an optical path of an optical output signal out of the PM fiber to produce a modified optical output signal, the optical delay device structured to cause an added optical delay greater than an optical delay between the two orthogonal polarization modes caused by the PM fiber in the optical output signal to produce the modified optical output signal;
a linear optical polarizer which is polarized in a direction to cause a mixing between the two orthogonal polarization modes in optical transmission light of the linear optical polarizer, the linear optical polarizer placed in an optical path of the modified optical output signal to produce the optical transmission light;
an optical interferometer located to receive the optical transmission light of the linear optical polarizer and structured to obtain optical interference of light between the two orthogonal polarization modes in the PM fiber; and
a processing device that processes the obtained optical interference to identify spatial positions and spatial widths of polarization cross talks between the two orthogonal polarization modes in the PM fiber at the induced series of polarization crosstalk peaks, and uses the determined spatial positions and spatial widths of the induced polarization crosstalk peaks to extract one or more polarization-related parameters of the PM fiber,
wherein the processing device extracts a birefringence thermal coefficient of the PM fiber based on both (1) a shift in spatial position of one of the polarization crosstalk peaks and (2) the known spacing between two adjacent stressed and periodic spatial locations as defined by the spatially periodic structure.
10. The device as in claim 9 , wherein the one or more polarization-related parameters of the PM fiber include birefringence (or a beat length) of the PM fiber.
11. The device as in claim 9 , wherein the one or more polarization-related parameters of the PM fiber include a spatial birefringence variation along the PM fiber.
12. The device as in claim 9 , wherein the one or more polarization-related parameters of the PM fiber include birefringence dispersion of the PM fiber.
13. The device as in claim 9 , wherein the one or more polarization-related parameters of the PM fiber include a birefringence temperature coefficient of the PM fiber.
14. The device as in claim 9 , wherein the processing device uses the determined spatial positions and spatial widths of the induced polarization crosstalk peaks to extract a collection of polarization-related parameters of the PM fiber including birefringence (or a beat length) of the PM fiber, birefringence variation along the PM fiber, birefringence dispersion of the PM fiber, and a birefringence temperature coefficient of the PM fiber.