US 12,085,749 B2
Optical fiber evaluation device and optical fiber evaluation method
Nobutomo Hanzawa, Musashino (JP); Takashi Matsui, Musashino (JP); Yuto Sagae, Musashino (JP); and Kazuhide Nakajima, Musashino (JP)
Assigned to NIPPON TELEGRAPH AND TELEPHONE CORPORATION, Tokyo (JP)
Appl. No. 18/009,784
Filed by NIPPON TELEGRAPH AND TELEPHONE CORPORATION, Tokyo (JP)
PCT Filed Jun. 24, 2020, PCT No. PCT/JP2020/024854
§ 371(c)(1), (2) Date Dec. 12, 2022,
PCT Pub. No. WO2021/260855, PCT Pub. Date Dec. 30, 2021.
Prior Publication US 2023/0221487 A1, Jul. 13, 2023
Int. Cl. H04B 10/00 (2013.01); G02B 6/02 (2006.01); H04J 14/00 (2006.01)
CPC G02B 6/02042 (2013.01) [G02B 6/02342 (2013.01)] 4 Claims
OG exemplary drawing
 
1. An optical fiber evaluation equipment, comprising:
an image capture unit that captures a cross-sectional image at one end of a multi-core optical fiber; and
a computation circuit that performs:
approximating a circumference of a cladding of the multi-core optical fiber by a circle based on the cross-sectional image;
determining a center and diameter of the circle as a center and diameter of the multi-core optical fiber, respectively and defining any coordinate system with an origin at the center of the multi-core optical fiber on the cross-sectional image;
detecting measurement centers that are centers of cores of the multi-core optical fiber from the cross-sectional image;
overlaying, on the cross-sectional image, design centers that are the centers of cores on design of the multi-core optical fiber, with the origin at a center on design of the multi-core optical fiber;
detecting an inter-core distance between the measurement center and the design center for each core of the multi-core optical fiber and calculating an average value or mean-square value of the inter-core distances of all the cores of the multi-core optical fiber;
deriving a rotation angle in the coordinate system, the rotation angle minimizing the average value or mean-square value; and
determining each of the inter-core distances at the rotation angle as an amount of deviation of each core of the multi-core optical fiber.