Optical Fiber Preform Refractive Index Profile Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for manufacturing optical fibers, such as dispersion-shifted and highly nonlinear dispersion-shifted fibers, face challenges in maintaining consistent profile shape parameters and optical characteristics over long lengths due to difficulties in measuring and controlling the core portion diameter and refractive index profiles, leading to variations in chromatic dispersion and zero dispersion wavelength.
Innovation Solution
A method involving the preparation of an intermediate preform, precise measurement of refractive index profiles, demarcation of the outer diameter shape, grinding to achieve a uniform diameter, and elongation to produce an optical fiber preform with controlled characteristics, ensuring consistent chromatic dispersion and zero dispersion wavelength across the fiber length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the core portion diameter is reduced to 10 μm or less to achieve desired optical characteristics, then the optical performance is improved, but the measurement precision of the core portion shape deteriorates
Solution Approach 1:
The patent introduces a reference mark as an intermediary element that enables accurate measurement of the core portion shape. The reference mark with known dimensions serves as a calibration standard, allowing the measurement system to accurately determine the core portion diameter and shape even when the core is extremely small (10 μm or less). This intermediary reference structure bridges the gap between the measurement system's capabilities and the required measurement precision for ultra-small core portions.
2Reliability
If the relative refractive index difference Δ is increased to 1% or more to achieve desired optical characteristics, then the optical performance is improved, but the measurement precision of the refractive index profile deteriorates
Solution Approach 1:
The patent uses the reference mark as an intermediary that provides a known refractive index profile for calibration. By comparing the measured profile against the known reference mark profile, the system can accurately determine the actual refractive index distribution in the core portion, even when the relative refractive index difference is large (1% or more), which would otherwise cause measurement errors.
3Ease of manufacture
If conventional measurement methods are used to determine the outer diameter of the preform, then the manufacturing process is simple, but the manufacturing precision of the final optical fiber deteriorates due to wide variation in chromatic dispersion
Solution Approach 1:
The patent performs preliminary measurement and calculation of the core portion shape and refractive index profile before completing the preform manufacturing. By measuring the intermediate preform, calculating the actual core portion characteristics, and determining the required outer diameter adjustment beforehand, the system ensures that the final preform will produce optical fibers with chromatic dispersion within the desired range, preventing defects before they occur.
Solution Approach 2:
The patent implements a feedback mechanism where the measured core portion shape and refractive index profile are used to calculate and determine the appropriate outer diameter of the preform. This feedback loop ensures that the preform dimensions are precisely controlled based on actual measurements, thereby guaranteeing that the final optical fiber will have chromatic dispersion within the specified range.
Data Source
AI summary
Provided is a method of manufacturing an optical fiber preform from which an optical fiber having the desired characteristics can easily be produced. The method comprises the steps of: (1) preparing an intermediate preform for manufacturing an optical fiber preform; (2) measuring a refractive index profile in a radial direction at each of a plurality of positions in the longitudinal direction of the intermediate preform; (3) demarcating the outer diameter shape of the intermediate preform based on the result of the step of measuring the refractive index profile so that an optical fiber preform can be manufactured such that an optical fiber having the desired characteristics may be produced from the optical fiber preform; (4) elongating the outer periphery of the intermediate preform so that the outer diameter shape may be formed as demarcated in the step of demarcating the outer diameter shape; and (5) drawing, so as to have a substantially constant outer diameter, the intermediate preform that has been subjected to the grinding step.