Cable itself, single mode is cheaper than multi mode fiber. But for overall cost, including the cost of the transceiver, the cost of single mode "system" is much expensive.
e.g
From Amazon
Fiber cost
Multi mode 500 ft 50/125 is $ 229.95 (page archived at https://archive.is/M69VR)
Single mode 500 ft 9/125 is $99.99 only (page archived at https://archive.is/BDSOe)
The youtube video provide a clear explanation.
https://youtu.be/OFcvpaQThA8?t=132
What is multi mode optical fiber video
https://www.youtube.com/watch?v=6xYOzY4zj0o
Fiber Optic Connector Types Explained in Details
https://www.youtube.com/watch?v=4Ovqe3XjRqM
A discussion forum about if single mode can work with multi mode, normally no, depends on a lot of factor, such as the characteristics of the transceiver and the fiber itself etc. (archived here)
==========================================================================
Optical Fiber Tutorial (from lansharck.com)
Fiber Specifications
The usual fiber specifications you will see are size, attenuation and bandwidth. While manufacturers have other specs that concern them, like numerical aperture (the acceptance angle of light into the fiber), ovality (how round the fiber is), concentricity of the core and cladding, etc., these specs do not affect you.
Fiber Itself
Fiber Optics, as we said, is sending signals down hair-thin strands of glass or plastic fiber. The light is "guided" down the center of the fiber called the "core". The core is surrounded by a optical material called the "cladding" that traps the light in the core using an optical technique called "total internal reflection." The core and cladding are usually made of ultra-pure glass, although some fibers are all plastic or a glass core and plastic cladding. The fiber is coated with a protective plastic covering called the "primary buffer coating" that protects it from moisture and other damage. More protection is provided by the "cable" which has the fibers and strength members inside an outer covering called a "jacket".
Multimode & Singlemode Fibers
Multimode & Singlemode fiber are the two types of fiber in common use. Both fibers are 125 microns in outside diameter - a micron is one one-millionth of a meter and 125 microns is 0.005 inches- a bit larger than the typical human hair. Multimode fiber has light traveling in the core in many rays, called modes. It has a bigger core (almost always 62.5 microns, but sometimes 50 microns ) and is used with LED sources at wavelengths of 850 and 1300 nm (see below!) for slower local area networks (LANs) and lasers at 850 and 1310 nm for networks running at gigabits per second or more. Singlemode fiber has a much smaller core, only about 9 microns, so that the light travels in only one ray. It is used for telephony and CATV with laser sources at 1300 and 1550 nm. Plastic Optical Fiber (POF) is large core ( about 1mm) fiber that can only be used for short, low speed networks.
Step index multimode was the first fiber design but is too slow for most uses, due to the dispersion caused by the different path lengths of the various modes. Step index fiber is rare - only POF uses a step index design today. Graded index multimode fiber uses variations in the composition of the glass in the core to compensate for the different path lengths of the modes. It offers hundreds of times more bandwidth than step index fiber - up to about 2 gigahertz.
Singlemode fiber shrinks the core down so small that the light can only travel in one ray. This increases the bandwidth to almost infinity - but it's practically limited to about 100,000 gigahertz - that's still a lot!
Size Matters
Fiber, as we said, comes in two types, singlemode and multimode. Except for fibers used in specialty applications, singlemode fiber can be considered as one size and type. If you deal with long haul telecom or submarine cables, you may have to work with specialty singlemode fibers.
Multimode fibers originally came in several sizes, optimized for various networks and sources, but the data industry standardized on 62.5 core fiber in the mid-80s (62.5/125 fiber has a 62.5 micron core and a 125 micron cladding.) Recently, as gigabit and 10 gigabit networks have become widely used, an old fiber has been revived. The 50/125 fiber was used from the late 70s with lasers for telecom applications before singlemode fiber became available. It offers higher bandwidth with the laser sources used in the gigabit LANs and can go longer distances. While it still represents a smaller volume than 62.5/125, it is growing.
Fiber Types and Typical Specifications
Core/Cladding | Attenuation | Bandwidth | Applications/Notes |
| Multimode Graded-Index | |||
| @850/1300 nm | @850/1300 nm | ||
| 50/125 microns | 3/1 dB/km | 500/500 MHz-km | Laser-rated for GbE LANs |
| 50/125 microns | 3/1 dB/km | 2000/500 MHz-km | Optimized for 850 nm VCSELs |
| 62.5/125 microns | 3/1 dB/km | 160/500 MHz-km | Most common LAN fiber |
| 100/140 microns | 3/1 dB/km | 150/300 MHz-km | Obsolete |
| Singlemode | |||
| @1310/1550 nm | |||
| 8-9/125 microns | 0.4/0.25 dB/km | HIGH! ~100 Terahertz | Telco/CATV/long high speed LANs |
| Multimode Step-Index | |||
| @850 nm | @850 nm | ||
| 200/240 microns | 4-6 dB/km | 50 MHz-km | Slow LANs & links |
| POF (plastic optical fiber) | |||
| @ 650 nm | @ 650 nm | ||
| 1 mm | ~ 1 dB/m | ~5 MHz-km | Short Links & Cars |
CAUTION: You cannot mix and match fibers! Trying to connect Singlemode to Multimode fiber can cause 20 dB loss - that's 99% of the power. Even connections between 62.5/125 and 50/125 can cause loss of 3 dB or more - over half the power.
=============================================================================
http://www.multicominc.com/training/technical-resources/single-mode-vs-multi-mode-fiber-optic-cable/
Fiber Optics is sending signals down hair-thin strands of glass or plastic fiber. The light is “guided” down the center of the fiber called the “core”. The core is surrounded by a optical material called the “cladding” that traps the light in the core using an optical technique called “total internal reflection.”
The core and cladding are usually made of ultra-pure glass. The fiber is coated with a protective plastic covering called the “primary buffer coating” that protects it from moisture and other damage. More protection is provided by the “cable” which has the fibers and strength members inside an outer covering called a “jacket”.
Single Mode Fiber Optic Cable
Single Mode fiber optic cable has a small diametral core that allows only one mode of light to propagate. Because of this, the number of light reflections created as the light passes through the core decreases, lowering attenuation and creating the ability for the signal to travel faster, further. This application is typically used in long distance, higher bandwidth runs by Telcos, CATV companies, and Colleges and Universities.Multimode Fiber Optic Cable
Multimode fiber optic cable has a large diametral core that allows multiple modes of light to propagate. Because of this, the number of light reflections created as the light passes through the core increases, creating the ability for more data to pass through at a given time. Because of the high dispersion and attenuation rate with this type of fiber, the quality of the signal is reduced over long distances. This application is typically used for short distance, data and audio/video applications in LANs. RF broadband signals, such as what cable companies commonly use, cannot be transmitted over multimode fiber.What’s Happening Inside The Multimode Fiber
Step-Index Multimode Fiber
Due to its large core, some of the light rays that make up the digital pulse may travel a direct route, whereas others zigzag as they bounce off the cladding. These alternate paths cause the different groups of light rays, referred to as modes, to arrive separately at the receiving point. The pulse, an aggregate of different modes, begins to spread out, losing its well-defined shape. The need to leave spacing between pulses to prevent overlapping limits the amount of information that can be sent. This type of fiber is best suited for transmission over short distances.
Graded-Index Multimode Fiber
Contains a core in which the refractive index diminishes gradually from the center axis out toward the cladding. The higher refractive index at the center makes the light rays moving down the axis advance more slowly than those near the cladding. Due to the graded index, light in the core curves helically rather than zigzag off the cladding, reducing its travel distance. The shortened path and the higher speed allow light at the periphery to arrive at a receiver at about the same time as the slow but straight rays in the core axis. The result: digital pulse suffers less dispersion. This type of fiber is best suited for local-area networks.
======================================================================================
http://www.blackbox.com/resources/blackboxexplains.aspx?id=bbe_2124
Black Box Explains...Multimode vs. single-mode Fiber.. (from Blackbox)
Multimode vs. single-mode. Multimode cable has a large-diameter core and multiple pathways of light. It can be used for most general data and voice applications, such as adding segments to an existing network.
Multimode comes in two core sizes and four varieties: 62.5-micron OM1, 50-micron OM2, 50-micron OM3, and 50-micron OM4. (OM stands for optical mode.) All have the same cladding diameter of 125 microns, but 50-micron fiber cable has a smaller core (the light-carrying portion of the fiber). Although all can be used in the same way, 50-micron cable, particularly laser-optimized OM3 and OM4 50-micron cable, provides longer link lengths and/or higher speeds and is recommended for premise applications (backbone, horizontal, and intrabuilding links) and should be considered for new installations. OM3 and OM4 can also be used with LED and laser light sources.
Single-mode cable (OS1, OS2) has a small (8–10-micron) glass core and only one pathway of light. (OS stands for optical single-mode.) With only a single wavelength of light passing through its core, single-mode realigns the light toward the core center instead of simply bouncing it off the edge of the core as multimode does. OS1 is applied to inside-plant tight-buffered cable. OS2 is applied to loose-tube cables.
Single-mode provides far greater distances than multimode cable and can go as far as 40 km so it’s typically used in long-haul network links spread out over extended areas, including CATV and campus backbone applications. Single-mode cable also provides higher bandwidth than multimode fiber.
Specification comparison
OM1 62.5-/125-Miron Multimode Fiber
850-nm Wavelength:
Bandwidth: 160 MHz/km;
Attenuation: 3.5 dB/km;
Distance: 220 m;
1300-nm Wavelength:
Bandwidth: 500 MHz/km;
Attenuation: 1.5 dB/km;
Distance: 500 m
OM2 50-/125-Micron Multimode Fiber
850-nm Wavelength:
Bandwidth: 500 MHz/km;
Attenuation: 3.5 dB/km;
Distance: 550 m;
1300-nm Wavelength:
Bandwidth: 500 MHz/km;
Attenuation: 1.5 dB/km;
Distance: 550 m
OM3 50-/125-Micron Multimode Fiber
850-nm Wavelength:
Bandwidth: 1500 MHz/km;
Attenuation: 3.5 dB/km;
Distance: 550 m;
1300-nm Wavelength:
Bandwidth: 500 MHz/km;
Attenuation: 1.5 dB/km;
Distance: 550 m
OM4 50-/125-Micron Multimode Fiber
850-nm Wavelength:
Bandwidth: 3500 MHz/km;
Attenuation: 3.5 dB/km;
Distance: 550 m;
1300-nm Wavelength:
Bandwidth: 500 MHz/km;
Attenuation: 1.5 dB/km;
Distance: 550 m
OS2 8–10-Micron Single-Mode Fiber
Premise Application:
Wavelength: 1310 nm and 1550 nm;
Attenuation: 1.0 dB/km;
Outside Plant Application:
Wavelength: 1310 nm and 1550 nm;
Attenuation: 0.1 dB/km
No comments:
Post a Comment