404
etc. In fiber-optic transmission systems, losses are unchanged at all transmission speeds in
the entire specified frequency range.
The peculiarities of fiber-optic transmission systems, in which there is fundamentally no
interaction of individual circuits that is significant for practice, are due to the fact that the
photon stream serves as the information carrier. The features of the optical range and the
element base used impose their limitations on the capabilities of the system.
The main
disadvantages of fiber-optic communication lines are: the susceptibility of optical fibers to
radiation, which causes the appearance of a darkening spot; hydrogen corrosion of glass,
which generates microcracks in the fiber.
The fiber optic transmission system model includes the following components:
a transmitter that converts an electrical signal into a light signal;
fiber-optic cable (the medium through which the light signal propagates),
consisting of an optical fiber and protective sheaths;
a receiver that receives a light signal and converts it back into an electrical
signal;
couplers (connectors) used to connect an optical fiber to a source,
a detector,
and to connect optical fibers to each other.
The selected fiber optic transmission system technology depends on the transmission
distance, customer applications, bandwidth requirements, and transmission speed. When
designing fiber optic transmission systems, it is important to determine the expected
growth in terms of data transmission volumes at the node (bandwidth reserve of
communication lines), since adding additional optical
fibers in the cable span, upgrading
installed cables is more expensive.
The choice of operating wavelength is dictated by the application used in the system. For
example, the FDDI (Fiber Distributed Data Interface) standard requires transmission at a
wavelength of 1300 nm. This wavelength is recommended to be used throughout the
network, which will eliminate problems with the compatibility of transmitting and
receiving equipment, duplication of spare parts and test and maintenance equipment.
Achieving a given transmission distance was previously achieved by the introduction of
optical and quantum technologies in two directions: the
development of new types of
optical fiber with attenuation close to the theoretical limit; the creation of optical
amplifiers that make it possible to sharply increase the power of optical signals at the line
input and compensate for losses in the optical fiber. In optical networks of the new
generation
NGN
(NextGenerationNetworks),
optical
access
networks
PON
(PassiveOpticalNetwork) are used to solve this problem.
With the growth of bandwidth and volume of traffic,
the problems associated, for
example, with the consequences of losses, are exacerbated. This requires additional control
and monitoring systems that allow you to control the operation of client equipment
directly from the technical support center. GPON technology has a built-in mechanism for
managing and monitoring network traffic, which guarantees high access speed and quality
of services provided. The higher the bandwidth and traffic volume, the greater the
responsibility and the more in demand additional control and monitoring systems become.
High-speed GPON access provides 40 Mbps channels (from the station to the service
consumer) per client. One promising HD (high definition) quality TV channel will require a
bandwidth of 20 Mbps. In particular, Motorola has developed an intermediate amplifier for
GPON
networks, which allows increasing the maximum distance between OLT and ONT
devices in a GPON network to at least 60 km.
The benefits of expanding the GPON network: significant savings in capital and
operating costs; single interface for optical fiber; easily upgradeable to 40 Gbps; easy
scalability and upgradeability; fault tolerance and traffic balancing; high-quality provision
