Light-emitting fiber
Optical fibers made of fluorescent substances are used. It is a part of the fluorescence generated when irradiated by light waves such as radiation and ultraviolet rays, and can be transmitted through the optical fiber closure. Luminescent fibers can be used to detect radiation and ultraviolet rays, perform wavelength conversion, or be used as temperature sensors and chemical sensors. In the detection of radiation, it is also called a flash fiber (Scintillation Fiber). Light-emitting optical fibers From the perspective of fluorescent materials and doping, plastic optical fibers are being developed.

Multicore fiber
A typical optical fiber consists of a core region and a cladding region surrounding it. But a multi-core fiber (Multi Core Fiber) has multiple cores in a common cladding region. Due to the proximity of the cores to each other, two functions are possible. One is that the spacing between the cores is large, that is, a structure that does not produce optocouplers. This optical fiber can improve the integration density per unit area of ​​the transmission line. In optical communication, ribbon cables with multiple cores can be made, while in non-communication fields, there are thousands of fiber cores used as optical fiber image beams. The second is to make the distance between the cores close, which can produce light wave coupling. Using this principle, dual-core sensors or optical circuit devices are being developed.

hollow fiber
The optical fiber is made hollow to form a cylindrical space, and the optical fiber used for light transmission is called a hollow fiber. Hollow core fibers are mainly used for energy transmission, which can be used for X-ray, ultraviolet and far infrared light energy transmission.
There are two types of hollow fiber structures:
One is to make the glass into a cylindrical shape, and its core and cladding principle is the same as that of the step type. Use the total reflection of light between air and glass to propagate. Since most of the light can propagate in the air without loss, it has a certain distance propagation function.
The second is to make the reflectivity of the inner surface of the cylinder close to 1 to reduce reflection loss. In order to improve the reflectivity, some dielectrics are set in the structure to reduce the loss in the working wavelength band. For example, it can achieve a loss of several dB/m at a wavelength of 10.6pm.