Description of the problem:
In addition to transmitting information, what are the other uses
Answer:
Fiber optics are not only used for the transmission of large quantities of information, but also, and generally most commonly used, for the transmission of images, for example, to allow engineers to check the radiation area of a nuclear power plant from a safe distance, and to provide a safe environment for the transmission of information. Fiber optics are also used in a variety of medical applications, such as endoscopes, which are flexible, bendable tubes containing several "optical fibers". When it is slipped into the patient's mouth, nose,
digestive tract, and other areas of the heart that are not visible from outside the body, the doctor can see internal changes through the endoscope,
reducing the need for risky surgery.
Fiber optics are used in a wide range of applications. In addition to being used for communication
purposes, fiber optics can also be used to make medical devices such as endoscopes, fiber optic sensors or fiber optic decorations, transportation, night vision
sensors for metrology, measurement, and control engineering, microscopy, microscope, machine vision, illumination, imaging, health,
charge-coupled devices (CCDs) in automobiles, and so on. etc. So it is gradually replacing copper wire as the main communication medium.
New technologies in fiber optic applications
In the late 1970s, fiber optic technology began to enter the commercial field, and some of the inherent characteristics of fiber optics (e.g., not subject to noise interference and high transmission bandwidth, etc.)
make it an ideal transmission medium for a variety of applications. Vertical trunks for high rate
systems have become the preferred design option for network designers
. The investment in optoelectronics on these vertical backbones is usually
compensated for in bandwidth and confidentiality. However, in the horizontal workspace,
the use of fiber optics has long been neglected. In the early 1980s, end-users began installing fiber optic cables to the information outlets of their workstations in the hope that cost-effective
fiber optic products would be available in the future, but the horizontal cables installed by most users operated in "dark" mode because the system optoelectronics could not meet the requirements of
This is because the system optoelectronics cannot achieve the required bandwidth and are too expensive.
Users lost interest in fiber-optic horizontal zone cabling due to the lack of cost-effective fiber-optic products. Recently, due to changes in cabling standards as well as advances in optoelectronic devices
, cables, connectors, and bandwidth escalation, many
users have begun to reconsider the use of fiber-to-the-desk as an alternative to copper in horizontal cabling systems
. Some of the technical issues and
standards associated with this are discussed below.
Advances in Fiber Optic Connector Technology
In recent years, fiber optic technology, such as fiber optic connectors, cables, and optoelectronic devices, has
come a long way. Changes in the physical size and form factor of fiber optic connectors (e.g., ST,
SC interfaces) have been of interest to product developers and end users.
Since many LAN applications require only two fibers (one for transmission and one for reception), dual fiber connectors are required in most cases. Dual fiber connectors are always much larger than the RJ45 jacks used for unshielded
shielded twisted pair (UTP) cabling systems, and given the density of connectors on the patch panel, unshielded twisted pair (UTP) cabling systems will be much more attractive.
The RJ45 jacks are also much larger than the RJ45 jacks used for unshielded twisted pair (UTP) cabling. At the workstation information outlet, dual fiber connectors also
have serious space issues - it is difficult to design panels and modules that can support more than 2 dual fiber connectors on a single-hole AFSL mounting box.
To address this issue, several manufacturers have developed small form factor dual
core fiber optic connectors that allow fiber optic connectors to compete in size with RJ45 connectors
. Several of these connectors are very creative in design and greatly reduce
the time required for fiber termination. Some vendors have also partnered with optoelectronic device manufacturers
to produce couplers in the same form factor to arrange LE
D/PIN pairs, supporting the production of new fiber optic connectors. However, the current EI
A/TIA TR41.8 recommendation states that SC Dual Fiber connectors will remain the standard fiber optic connector at the workstation end, while any fiber optic connector can be used at the intercom end. Regardless of what TR41.8 thinks about this issue, the development of small
size fiber optic connectors has made fiber optic connectors and UTP connectors roughly equivalent in size
size.
Developments in Fiber Optic Technology
The short wavelength is 850nm and the long wavelength is 1300nm. Table 1 gives
the separate operating windows for the two bands of multimode fiber. These operating windows are
determined by the attenuation characteristics of the fiber. However, after 1996, the attenuation characteristics of optical fibers have improved due to advances in fiber
manufacturing technology, allowing optical fibers to be used across the entire 720nm to 1370nm band. This is important for the development of wavelength division multiplexing
(WDM) systems.
Table 2 gives a comparison of the characteristics of 62.5nm and 50nm fibers in specific bands.
Both fiber core sizes can be used for LANs. It is clear from Table 2 that the bandwidth of 5
0nm fiber is wavelength-independent, which is a major advantage of 50nm fiber, however
Using 50
nm fiber incurs a 3dB energy degradation due to the difference in core size from the commonly used 62.5nm fiber. If the energy is large enough to accommodate this 3 dB attenuation in the worst-case link
scenario, then it increases the bandwidth to support more applications (such as Gigabit Ethernet) with a lot of bandwidth to spare
.
Since the signal attenuation of 62.5nm fiber is
greatest in the 820nm to 920nm band, why does it still operate in this band? Simply, it is because the optoelectronic devices (LEDs and PINs) are very inexpensive compared to their long wavelength counterparts, at about 30% of the price, making the use of shorter wavelength optoelectronic
devices very important.
Development of Fiber Optic Devices
Light Emitting Diodes (LEDs) and PIN Photodiodes are the most commonly used light source and light detector in short wavelength multimode optical
fibers. LEDs can support data rates
up to 125 Mbps. ordinary PINs are subject to high noise levels. In order to minimize the effect of noise, a mutual impedance amplifier is added to the PIN package, and this optical detector
is the PIN-FET component. The advantage of this device is that it is less expensive, but LE
D can support lower transmission rates, making it difficult to use it in high-speed data transmission
applications.
Lasers and APDs are another class of light sources and detectors used in fiber optic systems.
These devices can support very high data rates. These devices can support very high data rates.
APDs have high quantum efficiency, which makes them ideal for "low light" applications. However, both devices are complex, and keeping them stable
requires a high degree of electronic and temperature control. It is this complexity
that makes them expensive to apply and limits their use.
An exception to the "laser principle" is the vertical
cavity surface emitting laser (VCSEL), which operates in the short wavelength band. Its advantage over LEDs is that it is a semiconductor laser that can support transmission rates of up to 2Gbps. Moreover, it
has a low drive current, an output optical power of up to 1mW (0dBm), and a spectral width of less than
0.5nm. More importantly, it requires less circuitry, which greatly simplifies the design requirements and reduces the cost of the device.VCSELs are also better packaged than LEDs, and don't require prisms, so several VCSELs can be packaged together in a single base. Several VCSELs can form an array on the same substrate,
making them ideal for ribbon fiber and WDM applications.
These advantages make VCSELs an ideal light source, and the superior bandwidth performance of VCSELs
makes multimode fiber one of the best choices for Gigabit Ethernet applications. Table 3 gives a comparison between LEDs and VCSELs.
Fiber Standards
Users and network designers are increasingly concerned about electromagnetic interference/Radio Frequency Interference (
EMI/RFI), bandwidth, link distances, data security, and network failures
. The only medium that meets all of these criteria is optical fiber.
The introduction of the TIA/EIA TSB-72 standard in 1995 and the formation of the TIA Fiber Optic LAN Subgroup (FOLS) Short Wavelength Consortium in 1998 are the best evidence of this.
TSB-72 is a standard for centralized fiber optic cabling systems. TSB-72
allows for fiber optic cabling distances of up to 300 meters, allowing network designers to take advantage of the long distances to centralize network electronics (such as routers, hubs, and switches
) into one equipment room. p>) into a single device room. This architecture gives users a way to transition from the current
******* bandwidth environment to a switched environment. The centralized network architecture
increases network flexibility, simplifies network expansion, movement, change and
management, reduces network downtime, and most importantly, significantly reduces
installation costs.
100Mbps Fast Ethernet is one of the fastest growing LAN applications
The 1995 IEEE802.3u 100BASE-FX standard defines the standard for Fast Ethernet over fiber-optic media. 100BASE-FX standard uses the FDDI standard for signaling
The 100BASE-FX standard is based on the FDDI standard. The 100BASE-FX standard uses the signaling
encoding (4B5B encoding) method of the FDDI standard and the physical media signaling portion. It uses long-wavelength (1300 nm) optoelectronics, which are significantly more expensive than short-wavelength (850 nm) optoelectronics (as described earlier). As a result, the IEEE is currently developing a new standard, 100BA
SE-SX, and a number of interested vendors have formed the Short Wavelength Consortium in the first quarter of 1998.
Its mission is to develop a standard for the use of low-cost, low-wavelength optoelectronics. Its mission is to develop standards for fast
Ethernet using low-cost short-wavelength fiber optic devices. Note that this is very important. Its short-term goals are:
1. Reduce cost, i.e., use common optoelectronic devices, by using short-wavelength optoelectronic devices (LEDs and PINs) that have already been developed
.
2. The 100BASE-SX standard will be compatible with the 10BASE-FL standard.
3. connectors can be used.
4. Easy upgrade to 100Mbps.
Media Conversion
A complete consideration of a fiber-to-the-desktop solution requires not only fiber
information outlets (ST, SC, flat or angled, etc.) and fiber distribution enclosures (ST
, SC, wall-mounted, cabinet-mounted, tiltable, etc.), but it also
Need to consider the fiber directly to the desktop after the computer network cards and hubs and other equipment
.
Therefore, in the many fiber-to-the-desk solutions, many technical people
will come across the cost of network equipment will increase a lot of such a very realistic
problem, that is, we usually use the computer NICs will be replaced with fiber-optic NICs,
ordinary hubs of RJ45 outlets can not be used again, but by the pure fiber-optic out of the hub
The main reason is that the computer NICs will be replaced with fiber-optic NICs, and the hubs will be replaced with fiber-optic outlets. p>
Hubs with pure fiber optic outlets have been replaced. Due to fiber-optic cards and optical export hub prices
very expensive, resulting in the entire system cost increases, so fiber to the desktop now
in the country is still basically only on paper.
A very practical way to achieve fiber to the desktop is to use the media converter
converter (i.e., photoelectric converter). This device makes LAN upgrades very simple
and protects the investment in copper LAN equipment.