2018年3月12日星期一

FAQs on Fibre Optics

by Fiber-MART.COM
How to classify fibre optic cable?
 
It is a broad question.
 
a. By NEC - UL - flame retardancy;
b. By cable types (tight buffer/distribution/breakout/loose tube);
c. By fibre types:
 
Multimode fiber optic cable
Single-mode fiber optic cable
Hybrid fiber optic cable
d. Whether it has fibre and wire (composite cable).
 
What Type of fibre is Required to Run at Gigabit Network?
 
Depends on how far you want to go. Plain old FDDI fibre (160 MHz-km bandwidth at 850 nm and 500 MHz-km at 1300 nm ) will go ~240 m with a 850 VCSEL or 500 m with a 1300 laser. Practically every fibre manufacturer has 50/125 laser-optimized premium fibre (OM2/OM3/OM4) that will go a lot further -as far as 2 km - and while it's more expensive, we recommend it for any backbone applications.
 
Is There Special Tools to Pull fibre Optic Cable or Copper Cable?
 
fibre pulling gear is similar to all cable pulling gear, with one big caveat: ALL fibre optic cables must be pulled by the strength members, which are usually kevlar fibres. You should not simply put a grip on the jacket and pull - that will ruin most cables.
 
When is it Viable to String fibre Cable Overhead?
 
There are two solutions: self-supporting aerial cable or regular cable lashed to a messenger (maybe even the old telephone wire!) Most cablers can help you with a suggestion of the proper cable types.
 
What is The Difference Between Indoor and Outside Cables?
 
Generally, outside cables are designed to resist water penetration by using a gell fill or dry water-blocking compounds and a polyethelene jacket. The new dry cables are getting very popular, since they can be made as distribution types which are easier to terminate. Many also have a PE jacket over a UL-rated PVC jacket so you can bring the cable into the building, strip off the outside jacket and run it anywhere in the building (not the 50 feet limit of PE.) Indoor or premises cable must be rated for flame retardance for safety and to meet code.
 
How soon will it be, until we are able to communicate via the internet/television by means of fibre optics?
 
The answer to this question is complicated. The Internet is all fibre optics today, as is most of the phone and CATV systems. It's only the final connections to the home that is still copper and activity in that area is very high in 2005. The telephone companies have been pushing DSL, but it is a flawed concept - bandwidth is heavily dependent on the length of the lines, so generally it's not much better than a telephone modem. CATV companies are happy with coax cable, as it has gigibit capability. Both complain fibre to the home is too expensive, but the alternatives are not many, forcing the issue from a competitive standpoint!
 
How many fibre optics would be required for a small town?
 
As to how much fibre is needed, that depends on the system used. Two fibres to the home are probably adequate (one transmits, the other receives.) Backbone cables are usually 72-288 fibres, since it is more economical to install large fibre count cables now and leave them dark. Several techniques exist to multiplex signals on the fibres, including frequency-division, time-division and wavelength-division multiplexing, so one pair of backbone fibres can serve thousands of connections.
 
What is the difference in connectorization in tight buffered and loose tube type of cables?
 
A tight buffer cable can be terminated directly. THe 900 micron coating on the fibre is rugged enough to allow the connnector to be connected directly and if there is a 3 mm jacket, it is crimped to the connector for strength.
 
A loose tube cable has 250 micron buffer on the fibre in it and is too fragile to attach a connector directly. It has be be used with a breakout kit that sleeves the fibre in a protective tube before termination.
 
What is modal bandwidth, and how does it effect what distances gigabit ethernet can travel over fibre?
 
Modal bandwidth is caused by the fact that light in multimode fibre travels in rays or "modes" that take different times to get to through the fibre, causing dispersion. The longer the fibre, the greater the effect. This is a major factor in the distance limitation of GBE and the incentive for fibre manufacturers to develop better multimode fibre.
 
While the worst case distance for 62.5/125 FDDI-spec fibre using a 850 nm VCSEL source is only 220 m, laser-optimized 50/125 fibre capable of 1 km is now available.
 
What the unrepeatered length limitations are for 62.5/125 multimode fibre for?
 
The answer is:
 
10BaseFX : 12.5 dB loss at 850 nm, could equal 4 km
100BaseFX: 2 km, bandwidth, not loss limited, depending on LED source
GBit Ethernet: 220 m at 850 nm (bandwidth limited, and this distance is likely to get longer) or 500 m at 1300 nm with a singlemode pigtailled laser.
These are on FDDI grade 62.5/125 multimode fibre, which has a bandwidth of 160 MH-km at 850 nm and 500 MHz-km at 1300 nm. 62.5/125 fibre with 500 MHz-km bw at 850 nm and 50/125 laser-optimized fibres are available, specifically designed for premises applications of GBE.
 
Where to Buy Fiber Optics?
 
Corning SMF-28e+
Fiber optic cable comes in lots of types, depending on where it will be installed. Where to buy fibre optic cable? As the best OEM fiber optic cable manufacturer, fiber-mart.com provides a wide range of quality optical fiber cables with detailed specifications displayed for your convenient selecting, such as corning fiber optic cable, aerial fiber cable and zipcord fiber optic cable, etc. Per foot price of each fiber cable is flexible depending on the quantities of your order, making your cost of large order unexpected lower.

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