Can a single optical fiber transmit a complete image, just like an endoscope?
This is a classic problem in optical engineering. In short: a standard single-core optical fiber cannot directly transmit a complete image (2D image). The reason endoscopes can transmit images is due to a “fiber image bundle” composed of tens of thousands of optical fibers, or by utilizing cutting-edge computational optical imaging technology.
Here’s a detailed explanation from the perspective of physics and general engineering principles:
1. Why Can’t Ordinary Single-Core Optical Fibers Transmit Images Directly?
A standard single-mode or multi-mode optical fiber has only one unified transmission channel in space.
- Single-Mode Fiber (SMF): Its core diameter is extremely narrow (typically around 9\ \mu\text{m} ), allowing only a single fundamental mode ( \text{LP}_{01} ) of light to pass at a given operating wavelength. It can only transmit a single intensity and wavelength signal at a time and lacks any spatial resolution. Therefore, it cannot carry two-dimensional spatial distribution information (images).
- Multi-Mode Fiber (MMF): It has a slightly larger core diameter (e.g., common sizes are 50\ \mu\text{m} or 62.5\ \mu\text{m} ). Although it allows hundreds or thousands of higher-order modes (spatial orbits) of light to transmit simultaneously, due to modal dispersion and intermodal coupling caused by fiber bending, lights of different modes travel at different speeds and become randomly mixed during transmission. If you project an image onto the input end of a multi-mode fiber, the phase and amplitude will be completely scrambled after transmitting a very short distance. At the output end, what appears is a uniformly mixed, random speckle pattern, and the image cannot be directly reconstructed.
2. How Do Endoscopes Achieve Image Transmission via Optical Fibers?
In medical and industrial endoscopes, the following methods are typically used for image transmission:
Method A: Coherent Fiber Bundle — The Principle of Classic Rigid/Flexible Scopes
As you mentioned, “one fiber transmits an image.” Inside the flexible tube of an endoscope, there is actually an “image bundle” composed of tens of thousands to hundreds of thousands of extremely thin optical fibers (each with a diameter of only a few micrometers) bundled together.
- Core Requirement: It must be a “Coherent Bundle.” This means that the spatial arrangement and geometric order of each individual sub-fiber in the input end must be strictly one-to-one corresponding (absolutely symmetrical) with the output end.
- Imaging Principle: Each sub-fiber is responsible for transmitting only one pixel ( \text{pixel} ) of the image. Light rays pass through the objective lens at the front and hit the input end of the image bundle. Each fiber performs its duty, transmitting the brightness and color of its assigned pixel to the output end, where they are reassembled to restore a complete two-dimensional image.
Method B: Computational Imaging with a Single Multi-Mode Fiber — Cutting-Edge Academic Research
In recent years, academia has successfully achieved image transmission using “only a single multi-mode fiber” through physical computation. However, this requires complex algorithms:
- Measure the transmission matrix ( \mathbf{T} ) of the optical fiber using a Spatial Light Modulator (SLM).
- Use algorithms or deep learning neural networks to “mathematically unscramble” the messy speckle pattern generated at the output end and infer the input image.
- Limitation: This system is extremely sensitive to fiber bending and temperature. If the fiber bends slightly, the original transmission matrix becomes invalid. It is currently difficult to widely popularize in daily and industrial scenarios.
3. OFSCN® (DaCheng YongSheng) Related Specialty Optical Fibers and Spatial Sensing Technology
Although DaCheng YongSheng (OFSCN®) does not produce flexible endoscope image bundles for video image transmission (as these products are not part of our core product line), we possess advanced proprietary R&D products in the fields of spatial geometric state sensing and multi-core fiber technology.
For example, in situations requiring the reconstruction of an object’s three-dimensional “spatial geometric image (shape),” multi-core fibers combined with Fiber Bragg Grating (FBG) technology can be used for high-precision 3D shape reconstruction:
- OFSCN® Multi-Core Fiber Bragg Gratings / FBG Bare Grating Arrays: Integrates multiple independent cores within a single optical fiber and inscribes high-precision Fiber Bragg Gratings. By measuring the minute changes in the grating wavelength within each core, the direction and degree of bending can be sensed in real-time.
- OFSCN® Fiber Bragg Grating 3D Shape Sensors: Using multi-core FBG, algorithms can reconstruct a real-time 3D curve image of the entire fiber’s position in 3D space. In applications like minimally invasive surgery and robotic arm control, which require “position and motion tracking,” it acts as a “spatial mapping” tool independent of cameras.
Related Product Standard Images:
In summary, a single ordinary single-core/multi-mode optical fiber cannot directly transmit images. It requires either “multi-fiber pixel combination” (image bundles) or “computational de-scrambling” methods. To reconstruct the spatial geometric state of a 3D object, multi-core FBG shape sensing technology can be utilized.