Special optical fibers are used at specific wavelengths, made of special materials and have special functions. It has a wide variety and develops rapidly.

Classification of special optical fibers

1.1 Polarization maintaining single-mode fiber

Polarized light is light whose vibration direction is inconsistent with the propagation direction. Linear polarized light refers to polarized light in which light waves vibrate only in a fixed direction. Polarization maintaining fiber refers to a single mode fiber that enables linearly polarized light input into the fiber to transmit independently and stably in the fiber.

Single polarization optical fiber - through special design and manufacturing process, one of the two linear polarization modes constituting the basic mode in the optical fiber is the guided mode, which can transmit with low loss. At the same time, the other mode is cut off or attenuated due to serious leakage, so that the output light of this optical fiber always has only one polarization mode.

Infrared optical fiber - transmission wavelength is 2~4 μ M optical fiber of optical signal or optical information in the mid infrared band. In the wide band, the dispersion is very low, and the sensitivity to radiation is also very low. It can be used for ultra long distance without relay. Super large capacity communication system, anti radiation communication system, infrared optical fiber sensor and nonlinear optical element, infrared energy transmission line, etc. Infrared fiber bundles can be used in various infrared light sources, endoscopes, encoders and fiber optic panels.

Plastic optical fiber optical fiber made of transparent plastic with high refractive index core and low refractive index cladding. The diameter is tens of micrometers to several millimeters. Compared with glass fiber, it is light in weight, good in toughness, low in cost and simple in process; The transmissivity in the far infrared and ultraviolet bands is 50% higher than that of optical glass, and the transmissivity in the visible and near infrared bands is close to that of optical glass. The loss of plastic optical fiber is generally 100~200dB/km. Used together with LED, it can be used to transmit low rate optical communication systems within 120m. It can also be used as a beam transmitting device. Manufacturing materials mainly include polystyrene, polymethacrylate, polycarbonate, etc.

Radiation resistant optical fiber -- optical fiber made of radiation resistant material can work normally in he radiation environment. Generally, glass fiber will lose its light transmission ability due to dyeing when it is radiated by he. Glass containing cerium has good radiation resistance, which can be used to make optical fiber to obtain better results.

1.2 Large core diameter and large numerical aperture optical fiber

The core diameter and numerical aperture are greater than the nominal value, that is, the core diameter is greater than 62.5 μ m, and the numerical aperture is greater than 0.23 μ m. Compared with ordinary optical fiber, this kind of optical fiber has large loss and low bandwidth, and can be used in systems with special requirements. Image transmission fiber bundle - a fiber optic element used to transmit images, which is composed of tens of thousands to hundreds of thousands of bare optical fibers with a diameter of 10 microns to 20 microns, with fiber cores and cladding arranged in a dense and regular manner. It is mainly used for monitoring, endoscopy, periscope, etc. in industry, medicine and national defense. The position of each fiber on its two ends is strictly corresponding. There are two main types of image transmission fiber. One is to use optical glass to make a single fiber and then arrange it into bundles, with good flexibility, high brightness, large size, low resolution and small light transmission wavelength range. The other is made of tens of thousands to hundreds of thousands of quartz glass fibers, with good light transmittance, wide light transmission wavelength range, high resolution, and use length of tens of meters. Wider application.

1.3 Double clad optical fiber

Divided into dispersion shifted fiber (DSF) and dispersion flattened fiber (DFF): dispersion flattened fiber is suitable for wavelength division multiplexing systems, which can increase the transmission capacity several times to dozens of times.

1.4 Triangular core optical fiber

It is an improved dispersion shifted fiber with a large effective area, which is conducive to improving the optical power of the input fiber and increasing the transmission distance.

1.5 Optical fiber bundle

A large number of optical fibers are randomly arranged and put into a sheath to form a channel for light transmission. The monofilament diameter is 30~100 μ m. The main technical indicators are numerical aperture, light transmittance and minimum bending radius. The beam transmission can flexibly change the direction of light transmission or the position of the light source, and can also change the shape of the two end faces or divide the ends into several strands to change the shape of the light source and make a spatial distribution converter and distributor of light energy. As a light transmitting element, it is widely used in industry and medicine.