Optical Fiber Current Sensor with Opposite Windings
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Solution Overview
Problem
Existing optical fiber-based current measuring equipment faces challenges in accurately measuring low current values and direct current, often requiring filters to mitigate noise, which can be impractical or ineffective.
Innovation Solution
The equipment employs a configuration with two optical fiber windings of equal length but opposite orientation, using a splitter and Faraday mirrors, allowing for precise current measurement by combining cross signals to achieve high signal/noise ratio and eliminate noise without filters, while also accounting for fiber attenuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If filters are used to mitigate noise in existing optical fiber-based current measuring equipment, then noise is reduced, but the measurement of low current values and direct current becomes impractical or ineffective
Solution Approach 1:
The measurement system is segmented into two separate sensing branches: a first sensing branch for measuring current in a first conductor and a second sensing branch for measuring current in a second conductor. Each branch independently measures current without being affected by noise from the other conductor, enabling accurate measurement of low current values and direct current without requiring filters that would block the desired signal.
Solution Approach 2:
The patent introduces an intermediary processing mechanism that combines the measurements from both sensing branches. By processing the differential signals from the two branches, the system eliminates common-mode noise while preserving the actual current measurements, achieving both noise reduction and accurate low current measurement without using traditional filters.
2Measurement precision
If a single sensing branch is used in existing equipment, then the device complexity is low, but the dynamic range and precision for low current measurement are insufficient
Solution Approach 1:
The single sensing branch is divided into two separate sensing branches, each with its own optical fiber winding, polarizer, and detection path. This segmentation enables differential measurement that significantly improves precision for low current values while maintaining a modular architecture that manages complexity through functional separation.
Solution Approach 2:
The two-sensing-branch configuration serves multiple functions: it measures current in two different conductors simultaneously, provides differential noise rejection, extends the dynamic range of measurements, and enables accurate direct current measurement. This multi-functionality justifies the increased structural complexity by delivering superior measurement capabilities across multiple operating conditions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enables precise and high dynamic range current measurement, particularly for low current values and direct current, with improved noise cancellation and accurate fiber attenuation calculations.
Implementation Method 1
Optical fiber-based sensors for measuring the current circulating through a conductor are known. Said sensors work according to the Faraday effect, i.e., the magnetic field generated by the current circulating through the conductor causes a rotation in the polarization of light circulating through the optical fiber arranged around the conductor.
Implementation Method 2
a first sensing branch comprising a first optical fiber winding arranged in the proximity of the conductor and a first Faraday mirror
Data Source
Figure 1~2
AI summary
The invention relates to optical fiber-based measuring equipment for measuring the current circulating through at least one conductor (4), the measuring equipment (1) comprising an interrogator and a sensing portion (3) connected to the interrogator (2) and configured for being arranged in the proximity of the conductor (4). The sensing portion (3) comprises a first input branch (30) and a second input branch (31) coupled by means of a splitter (34) to a first sensing branch (32) and to a second sensing branch (33). The first sensing branch (32) comprises a first optical fiber winding (320) arranged in the proximity of the conductor (4), and the second sensing branch (33) comprises a second optical fiber winding (330) arranged in the proximity of the conductor (4), the first optical fiber winding (320) and the second optical fiber winding (330) comprising the same number of turns that are, however, wound in opposite directions. The invention also relates to a method for measuring current.