A fiber optic cable

A fiber optic cable is a communication cable consisting of two or more glass or plastic optical fiber cores within a protective cladding covered by a plastic PVC outer sleeve. Signal transmission along the internal fiber optics typically uses infrared light.

A dielectric waveguide that transmits light waves. Optical fiber is a kind of fiber composed of two layers of transparent media in concentric circles. The most widely used dielectric material is quartz glass (SiO2). The inner medium, called the core, has a higher refractive index than the outer medium (called the cladding). The refractive index of the core or cladding is adjusted by doping germanium, phosphorus, fluorine, boron and other impurities in the quartz glass. The transmission wavelength of optical fiber for communication is mainly near-infrared light of 0.8-1.7 microns. The core diameter of the optical fiber varies from type to type, usually a few microns to 100 microns, and most of the outer diameters are about 125 microns. It has a plastic covering on the outside. Optical cables are made by combining single or multiple optical fibers and strengthening and protecting them. Fiber optic cables can be used in a variety of environments. Optical cables are manufactured in a similar way to electrical cables.

fiber optic cable

Optical fiber communication is one of the important ways of modern information transmission. It has the advantages of large capacity, long relay distance, good confidentiality, no electromagnetic interference and copper saving.

The report utilizes the market data collected from long-term tracking of the optical fiber and cable industry market, and constructs an analysis system from the overall height of the industry. The report mainly analyzes the development status and prospects of China’s optical fiber and cable industry; the pattern and concentration of the optical fiber and cable industry; and the technical status of the optical fiber and cable industry.

3G network construction, FTTH (fiber-to-the-home) implementation, triple-network integration pilot , village-to-village project in the west, and “fiber into copper retreat”, China’s optical fiber and cable industry has a good momentum of development, and China has become the world’s largest The main fiber optic cable market and the world’s largest fiber optic cable manufacturing country, and has achieved remarkable achievements.

In 2011, there were 149 enterprises above designated size in China’s optical fiber and cable industry , a decrease of 21 from the previous year; the total industrial output value was 68.802 billion yuan; the sales revenue was 64.310 billion yuan, a year-on-year increase of 24.68%; the profit was 6.554 billion yuan, a year-on-year increase of 4.739 billion %.

With the adoption of FTTH and FTTC systems in my country, the integration of three networks and the continuation of large-scale 3G construction, the market demand for optical fiber and cable is still very large, which provides a strong impetus for the development of my country’s optical fiber and cable industry, and the industry has a bright future.

As the competition in the optical fiber and cable industry continues to intensify, mergers and acquisitions among large optical fiber and cable companies and capital operations are becoming more frequent, domestic excellent optical fiber and cable manufacturers are paying more and more attention to the research of the industry market, especially the development environment of enterprises and customer demand trends An in-depth study of changes. Because of this, a large number of excellent domestic optical fiber and cable brands have risen rapidly and gradually become leaders in the optical fiber and cable industry!

The birth and development of optical fiber communication is an important revolution in the history of telecommunications. The informatization construction of human society is accelerating. Even in the case of global economic downturn, the communication and information industry is still very hot. Optical fiber communication is developing in the direction of high-speed, ultra-high-speed, ultra-large-capacity optical fiber transmission and all-optical networks. In the process of realizing informatization in our country, during the “Ninth Five-Year Plan” period, China Telecom completed the laying of “eight vertical and eight horizontal” optical cable trunk lines. A backbone communication network with optical cable as the main body is gradually formed. The trunk line of high-capacity optical cables extending in all directions has become the “information channel” of our country. With the continuous development of the communication industry, optical cables have been laid from provinces to cities, counties and even towns. The date of “fibre-to-the-home” is getting closer. In recent years, with the advancement of technology, the reform of the telecommunication system and the gradual and comprehensive opening of the telecommunication market, and due to the huge demand for bandwidth brought about by the explosive development of IP services, the development of optical fiber communication has once again shown a booming trend. new situation.

Fiberglass has been used to transmit light for more than 30 years. The initial application of optical fiber was limited to certain optical machinery and medical equipment (such as light guidance and gastroscope, etc.), which transmitted visible light with an attenuation of up to 1000 decibels/km. In 1966, Kao first proposed the idea of using quartz-based glass fibers for long-distance optical information transmission. In 1970, a high- purity silica optical fiber was made by chemical vapor deposition in the United States , and its attenuation was reduced to 20 decibels/km, thus making long-distance transmission a reality. Afterwards, the attenuation of optical fiber decreased rapidly, and by the late 1970s it had dropped to the theoretical limit level of 0.2 decibels/km. The bandwidth of optical fiber is continuously increasing, and single-mode optical fiber with a bandwidth of hundreds of gigahertz kilometers has been available for practical use in the early 1980s. A fiber optic communication system with a relay distance of over 100 kilometers and a capacity of hundreds of megabits per second has been developed. Optical fiber communication equipment manufacturing has developed into a new industrial sector. The characteristics that the intensity and phase of light waves in optical fibers change with changes in physical quantities such as temperature, electric field, and magnetic field have been used in high-sensitivity telemetry sensors.

Fundamental

Optical fiber transmission is based on the principle of total reflection of available light at the interface of two media. Abrupt fiber , n 1 is the refractive index of the core medium, n 2 is the refractive index of the cladding medium, n 1 is greater than n 2, the light entering the core reaches the interface between the core and the cladding (referred to as the core-cladding interface) When the incident angle is greater than the critical angle of total reflection θ c, total reflection can occur and no light energy can pass through the fiber core, and the incident light can be transmitted forward through countless total reflections at the interface. turn out to be

When the fiber is bent, the interface normal turns and the incident angle is small, so the incident angle of some light rays becomes smaller than θc and cannot be totally reflected. However, those rays with larger incident angles can still be totally reflected, so the light can still be transmitted when the fiber is bent, but it will cause energy loss. Generally, when the bending radius is greater than 50-100 mm, the loss is negligible. Small bends will cause severe “microbend loss”.

The electromagnetic wave theory is often used to further study the mechanism of optical fiber transmission, and the wave equation is solved by the boundary conditions of the optical fiber dielectric waveguide. The light propagating in the optical fiber contains many modes, each mode represents an electromagnetic field distribution, and corresponds to a certain ray described in geometric optics. The conduction mode present in the fiber depends on the normalized frequency ν value of the fiber

formula

Where NA is the numerical aperture, which is related to the refractive index of the core and cladding medium. ɑ is the radius of the fiber core, and λ is the wavelength of the transmitted light. When the fiber is bent, mode coupling occurs, and a part of the energy is transferred from the conduction mode to the radiation mode, and is lost outside the core.

Performance: The main parameters of optical fiber include attenuation and bandwidth.

fiber attenuation

Factors that cause fiber attenuation include scattering loss, absorption loss, and microbending loss. Scattering loss is mainly produced by Rayleigh scattering, which is caused by the microscopic refractive index fluctuation caused by the irregular molecular structure of glass. It is the inherent loss of optical fiber and the lowest limit of optical fiber attenuation. It is inversely proportional to λ4 . When the wavelength is less than 0.8 microns, the Rayleigh scattering loss rises rapidly, which limits the use of optical fibers. The intrinsic absorption loss of the fiber matrix material SiO2 and doped oxide molecules makes the attenuation of the fiber increase rapidly when the wavelength is greater than 1.7 microns. Therefore, the use wavelength of this type of fiber is limited in the range of 0.8 to 1.7 microns. In this range, the attenuation is mainly due to the transition metal ions and OH- of impurities such as Fe++ + and Cu++ contained in the quartz glass. caused by the absorption loss. With the improvement of the purification process, the impurity absorption loss has been basically eliminated, thus reaching the limit of Rayleigh scattering loss. Irregular micro-bends of optical fibers cause mode coupling and cause micro-bend loss, so micro-bending of optical fibers should be avoided as much as possible during processing and use.