Light Interference Unit Noise Reduction via Fiber Path Design
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Solution Overview
Problem
Noise is generated in the whole waveform of the interference signal due to the fiber device's separation portion when laser light with a temporally swept emission wavelength is used in light interference units and measurement devices.
Innovation Solution
The light interference unit and measurement device incorporate a fiber device with a separation portion where the laser light is temporarily separated from the optical fiber core to an area with a different refractive index and then re-incident, with a transmission light path length equal to or greater than the reflection light path length, specifically using a reference light or measurement light device to minimize noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a fiber device with a separation portion is used to adjust light path, then light path adjustment function is achieved, but noise is generated in the interference signal waveform
Solution Approach 1:
The patent converts the harmful reflection light into a beneficial element by intentionally designing a reference light path that includes a separation portion. The reference light device is configured to generate reflection light that matches the measurement light's reflection characteristics, thereby converting the noise-source into a reference signal that helps cancel out similar noise in the measurement channel through differential processing
Solution Approach 2:
The reference light device acts as an intermediary that replicates the optical path characteristics of the measurement light device. By introducing a separate reference path with identical separation portion characteristics, the system creates a mediator that carries the same noise signature, enabling noise cancellation through comparison and differential measurement
2Measurement precision
If post-detection data processing is performed to remove noise, then measurement precision is improved, but processing time increases
Solution Approach 1:
The patent performs noise cancellation in advance by designing the optical system to inherently separate reference and measurement paths with matched characteristics. The reference light device is pre-configured to replicate the measurement path's reflection properties, so that when the lights are recombined, the noise components are already correlated and can be easily subtracted, reducing the need for complex post-processing
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 effectively decreases noise in the interference signal, allowing for more precise measurement and reducing the need for post-detection data processing, thereby shortening processing time.
Implementation Method 1
a light interference unit including a branching optical element, a multiplexing optical element and a fiber device... The multiplexing optical element multiplexes the reference light and the measurement light... and causes the reference light and the measurement light to interfere
Implementation Method 2
a fiber device which includes a separation portion in which the laser light introduced by an optical fiber is temporarily separated from a core of the optical fiber to an outside having a refractive index different from that of the core
Implementation Method 3
The multiplexing optical element multiplexes the reference light and the measurement light reflected by an object to be measured, and causes the reference light and the measurement light to interfere
Data Source
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AI summary
A light interference unit (20) includes a branching optical element (21), a multiplexing optical element (23), and at least one fiber device (22). The branching optical element (21) branches a laser light for which an emission wavelength is temporally swept, into a measurement light and a reference light. The multiplexing optical element multiplexes the reference light and the measurement light reflected by an object to be measured, and causes the reference light and the measurement light to interfere. The at least one fiber device includes a reference light device (22A). A transmission light path length is defined by a light path length of the reference light, which transmits the reference light device, from the reference light device to the multiplexing optical element. A reflection light path length is defined by a light path length of the reference light, which is reflected by a separation portion of the reference light device, from the reference light device to the multiplexing optical element. In this case, the transmission light path length is equal to or more than the reflection light path length.