Technical analysis: comparison of optical fiber transmission and wireless transmission

According to the traditional communication system model, its basic framework is: source-transmitter-transmission system-receiver-host
.
The transmission system (channel) is what we call the system model
composed of transmission media.
Since the transmission of signals in the channel is unidirectional and will be affected and interfered by noise, the appropriate selection of transmission media is of great significance
to improve the performance of signal transmission, that is, reliability and effectiveness.
Communication quality depends on the characteristics of the signal and the nature of the transmission medium, and the key is whether the signal spectrum characteristics and channel transmission characteristics
can be matched.
Transmission medium, in a narrow sense, refers to the transmission system between the transmitter and the receiver, which is aimed at the signal; Broadly speaking, it refers to the system between the source and the source, which is aimed at information
.
We divide the transmission media into two types: guided and non-directed, and the difference between the two is subject to the characteristics of the media itself and the signal itself
.
Guided and non-guided is what we often call wired communication and wireless communication
.
Wired communication is divided into four categories
: twisted pair, coaxial cable, overhead open wire and optical fiber.
Optical fiber, that is, optical fiber, is an extremely fine (50μm~100μm) and soft medium
that can conduct optical signals.
The cross-section of the optical fiber is circular and consists of three parts from the outside to the inside: shell, cladding, and core
.
The optical properties of the three are different: the fiber core is often composed of silica, which is the optical path;
。 The cladding consists of multiple layers of reflective glass fibers designed to reflect light onto the
core.
From the transmission point modulus, optical fiber can be divided into single-mode and multi-mode transmission modes, single-mode provides a single optical path; Multimode optical fiber, that is, divergence into multiple light waves, each light wave takes one path
.
Single-mode fiber has more capacity because of its low attenuation, but it is more expensive
to produce than multimode fiber.
Optical fiber can only be transmitted in one direction at any time, so to implement two-way communication, it must appear in pairs, one for input and one for output, with both ends of the fiber connected to the
optical interface.

Optical fiber has four significant advantages: First, large bandwidth and large
capacity.
At present, optical fiber has basically realized the practical application of engineering, which can not only meet the transmission needs of comprehensive business information such as telephone, data, text, and images, but also adapt to the development of
the information society in the future.
Compared with other wired transmission methods, optical fiber is currently the best performance transmission medium, through frequency division, time division and wavelength division multiplexing, it will be more and more used in daily life
.
Second, the loss is small and the relay distance is long
.
Optical fiber transmission loss does not change with frequency and temperature changes, so the installation of optical fiber does not need strict stability; Its long relay distance performance can be applied to submarine optical cable communication and defense long-distance communication, which is of great significance
for solving submarine communication.
Third, the anti-interference is good
.
Optical fiber is an insulating material, can only guide light but not conduction, so optical fiber is not subject to electromagnetic interference, therefore, it can not only prevent electromagnetic wave radiation from eavesdropping, but also prevent the influence of external interference signals, which plays an extremely important role
in improving the security and confidentiality of modern communications.
4.
Small size and light
weight.
Because the optical fiber can be multiplexed and the capacity is large, only a very small and very fine optical fiber is required to transmit a large number of signals, which reduces the cost
of transportation and construction.

The opposite of wired communication is unlimited communication, including radio wave communication, infrared communication and microwave communication
.
Since they all travel in a straight line and both need to have a line-of-sight pathway in terms of sending and receiving, they are also called line-of-sight media
.
Radio waves are omnidirectional and have a small frequency; Infrared frequency is minimal, often used for the detection of temperature-related things; The frequency of microwaves is somewhere in between, and it is directional, mainly taking advantage of its ability
to penetrate the ionosphere and enter space.
Now microwave is the most widely used, mainly divided into two types, namely terrestrial microwave relay communication and satellite communication
.
Since microwaves propagate in a straight line in space, and the surface of the earth is curved, their propagation distance on the ground is limited
.
In order to increase the transmission distance, the height of the antenna tower is increased, the higher the tower, the farther
the transmission distance.
Terrestrial microwave communication has the following main characteristics: high frequency, large bandwidth, long transmission distance, strong anti-interference ability, high
reliability.
However, due to its high frequency, there can be no obstacles between adjacent stations, and it is easily affected by weather and caused by distortion
.
The principle of satellite communication and ground microwave communication is similar, and its essence is to use artificial synchronous earth satellites located at an altitude of 36,000km as a kind of microwave relay communication
.
With three suitably configured satellites, it is possible to cover all parts of the globe except the two-level sound zone
.
The biggest advantage of satellite communication is that the communication is covered by the surface, and the electromagnetic waves emitted by synchronous satellites can radiate to one-third of the earth, so it is convenient to realize multiple access and mobile communications, and it is also convenient to form a communication network
.
Therefore, it is widely used to transmit multi-channel long-distance telephone, telegraph, television and other services, and we can enjoy live broadcasts
in other regions in different regions.
However, it also has its drawback, that is, it has too
much delay.
No matter how far apart the two stations on the ground, the delay from the transmitter to the receiver via satellite is 270us, which is much longer than other wireless communications, and because of this, satellite communications are less confidential.

Through the comparison of microwave, the representative of wired communication - optical fiber and wireless communication, we can see that each has its own advantages and disadvantages
.
Optical fiber is subject to the characteristics of the media itself, which requires the matching of the signal and the channel, which is the concept of the road; Wireless communication relies on the characteristics of the signal itself and is a field concept
.
This is the most basic difference
in their appearance.
With the rapid development of the economy, the research on transmission media has become more and more profound
.
Optical fiber can transmit signals at high speed and accurately, and the quality is light, easy to build, and the cost is low, but it is precisely because of its advantages that it also has great disadvantages, that is, it may not meet the construction requirements
.
For example, when communication lines have to pass through certain buildings, mountains, construction excavations, cable laying and other projects, they can only be bypassed, which is time-consuming and laborious, so optical fiber needs free space to show its talents
.
Wireless communication masks this shortcoming, which can be freely transmitted
through different obstacles by selecting different waves as carriers.
However, satellite communications also have significant drawbacks
.
It does not rely on a real medium to transmit signals, which can cause errors
.
For example, in microwave communication, sometimes the signal emitted by one antenna will also split into several slightly different paths to reach the antenna, resulting in distortion; During the transmission process, it will also be interfered
by greater environmental factors such as weather than wired transmission.

So, how to choose the transmission method? For example: when we want to build an office building, we have to choose the network coverage method, whether to choose to lay high-speed, lightweight optical fiber, or choose wireless network coverage: if we are fixed-point office, then of course we choose optical fiber, because its transmission rate is extremely high and stable; If you need to work on the move, then choose wireless communication, so that you can access the Internet anytime, anywhere without being limited by location, but then the network is not very stable
.
If you choose the communication between the seabed and the land, we generally choose optical fiber, although this laying will require a lot of materials, the signal will have a great time delay, require a lot of manpower, material resources, but if you choose wireless communication, due to the great resistance of seawater, the signal will have a great attenuation, resulting in a very short transmission distance.
.
.
Experts in Pinheng communication technology suggest that it should be selected according to needs and adapted to
local conditions.

According to the current research level of transmission media, optical fiber has great application prospects
in both civilian and military applications.

Shanghai Pinheng Building Intelligent Engineering Co.
, Ltd.
is a modern high-tech company specializing in the field of wireless communication, is a collection of wireless communication full range of products research and development, production, sales and service in one of the professional suppliers, the current products cover optical transmission, wireless intercom, microwave transmission and wireless bridge and other fields, have passed the non-commissioned radio testing, and widely used in the Internet, operators, government, finance, energy, manufacturing, education, medical and health, culture and sports, transportation and other industries, for user communication to create value
。

Shanghai Pinheng takes scientific and technological innovation as the guide, based on advanced manufacturing, has carried out a lot of R&D investment in wireless communication products, integrated into today's most advanced wireless communication technology, and has become the preferred partner
of many domestic weak current integrators, wireless private network system subcontractors, wireless intercom equipment agents and distributors.
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integrating project planning, survey and design, installation and commissioning, and system maintenance.
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from the majority of users.
Over the years, Shanghai Pinheng has steadily advanced on the road of independent research and development, leading and promoting the development of
China's cutting-edge network technology.