Fiber Optic Rotary Joint Gap Control for Low Insertion Loss
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Solution Overview
Problem
Existing fiber optic rotary joints face challenges in maintaining precise end-to-end relative position between optical fibers, leading to mechanical damage and high insertion loss due to large gaps, which are difficult to maintain without fiber contact, especially when using broadband light or multiple wavelengths.
Innovation Solution
A fiber optic rotary joint with a control system that uses a light intensity sensor to measure interference between fiber end faces and adjust the gap between them using a linear actuator, maintaining the gap constant through a feedback loop to prevent mechanical damage and minimize insertion loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If beam expansion optics (collimators) are used for beam transmission in a gap between stationary and rotating fibers, then positional accuracy requirements at the FORJ are reduced, but chromatic aberration creates challenges in systems with more than one working light wavelength or in systems using broadband light
Solution Approach 1:
The patent removes beam expansion optics (collimators) from the FORJ system entirely, replacing them with a direct fiber-to-fiber junction approach. This extraction eliminates the chromatic aberration problem caused by lenses while maintaining positional accuracy through precise alignment features and control mechanisms.
Solution Approach 2:
The patent replaces the optical-mechanical collimator system with a mechanically-controlled direct fiber junction system. Instead of using lenses to expand and transmit beams, the system uses precision mechanical alignment and control to maintain optimal fiber end-to-end positioning across different wavelengths.
2Reliability
If a larger gap between fibers is used, then the risk of fiber ends coming into contact and touching each other during rotation is reduced, but insertion loss of the rotary junction increases
Solution Approach 1:
The patent implements dynamic control of the fiber gap distance through a control system that adjusts the position of one fiber relative to the other. This dynamic adjustment maintains an optimal gap size that prevents fiber contact during rotation while minimizing insertion loss, adapting to different operating conditions in real-time.
Solution Approach 2:
The patent employs a feedback control system using light intensity sensors to monitor the gap between fiber ends and automatically adjust the fiber position to maintain optimal alignment. This closed-loop control ensures minimal insertion loss while preventing fiber contact during rotation.
3Loss of energy
If a smaller gap between fibers is used, then insertion loss of the rotary junction is reduced, but the risk of fiber ends coming into contact and touching each other during rotation increases
Solution Approach 1:
The patent uses dynamic positioning control to maintain a precisely optimized gap distance that is small enough to minimize insertion loss but large enough to prevent fiber contact during rotation. The system continuously adjusts fiber positions to maintain this optimal distance under varying operational conditions.
Solution Approach 2:
The feedback control system monitors light intensity to detect changes in fiber gap distance and automatically adjusts fiber positioning to maintain the optimal gap. This ensures minimal insertion loss while preventing fiber contact through real-time monitoring and adjustment.
4Reliability
If index matching lubricating liquid is used to reduce reflections from fiber ends and provide lubrication for the rotating fiber, then sealing elements such as rubber or plastic o-ring are required, which makes the rotary joint more costly and prone to malfunction
Solution Approach 1:
The patent eliminates the index matching lubricating liquid and associated sealing elements from the FORJ system. Instead, it uses direct fiber-to-fiber junction with precision alignment and control mechanisms to achieve low reflections and smooth rotation without requiring additional sealing components.
Solution Approach 2:
The patent replaces the lubricating liquid intermediary with a direct mechanical and optical coupling system. Precision alignment features and controlled fiber positioning serve as the intermediary mechanism to reduce reflections and enable smooth rotation without requiring liquid lubricants or sealing elements.
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 solution dynamically adjusts the gap between fiber ends to prevent mechanical damage and achieve optimal light transmission with minimal insertion loss, ensuring long operational lifetimes and efficient broadband light transmission.
Implementation Method 1
A light intensity sensor is adapted to measure light intensity changes due to optical interference between light reflected from the fibers' end faces
Implementation Method 2
An actuator is configured to axially translate at least one of the first and second optical fibers relative to the other in a reciprocal motion
Implementation Method 3
a control system is configured to receive light intensity measurements from the sensor and to use the light intensity measurements to control the reciprocal motion of the linear actuator to maintain the length of the gap between fibers' end faces substantially constant
Implementation Method 4
The FORJ is adapted to transmit light between the fibers' end faces
Data Source
AI summary
According to at least one embodiment of the present disclosure, there is provided an apparatus comprising: a first optical fiber in communication with a light source; a second optical fiber in communication with an imaging probe; and a fiber optic rotary joint (FORJ) where a distal end of the first optical fiber and a proximal end of the second optical fiber are positioned coaxially with a gap between the fibers' end faces. The FORJ is adapted to transmit light between the fibers' end faces, and to rotate at least one of first and second optical fibers relative to the other. An actuator is configured to axially translate at least one of the first and second optical fibers relative to the other in a reciprocal motion. A light intensity sensor is adapted to measure light intensity changes due to optical interference between light reflected from the fibers' end faces. And, a control system is configured to receive light intensity measurements from the sensor and to use the light intensity measurements to control the reciprocal motion of the linear actuator to maintain the length of the gap between fibers' end faces substantially constant.