Do single mode fiber optics have a higher data transfer rate than multi mode?
Topic: Do single mode fiber optics have a higher data transfer rate than multi mode?
April 25, 2019 / By Aldridge Question:
1) Do single mode fiber optics have a higher data transfer rate than multi mode?
1a) If so, why? At first glance it seems that since multi-mode can have multiple light rays transmitting in parallel, it should be able to transfer more data. Does signal dispersion really impact that much?
2) I'm trying to understand the point of multi-mode. I know it's made of cheaper material, so did they compensate by fitting multiple beams in to bring its data rate up to par?
3) Also, this may be naive but why not (or do they) make cable with the good quality material of single mode cables and the dimensions of multimode, and send multiple beams over a good quality material cable?
Best Answers: Do single mode fiber optics have a higher data transfer rate than multi mode?
Talisha | 9 days ago
Single Modem fiber is used in many applications where data is sent at multi-frequency (WDM Wave-Division-Multiplexing) so only one cable is needed - (single-mode on one single fiber)
Single Mode cable is a single strand (most applications use 2 fibers) of glass fiber with a diameter of 8.3 to 10 microns that has one mode of transmission. Single Mode Fiber with a relatively narrow diameter, through which only one mode will propagate typically 1310 or 1550nm. Carries higher bandwidth than multimode fiber, but requires a light source with a narrow spectral width. Synonyms mono-mode optical fiber, single-mode fiber, single-mode optical waveguide, uni-mode fiber.
Single-mode optical fiber is an optical fiber in which only the lowest order bound mode can propagate at the wavelength of interest typically 1300 to 1320nm.
Multi-Mode cable has a little bit bigger diameter, with a common diameters in the 50-to-100 micron range for the light carry component (in the US the most common size is 62.5um). Most applications in which Multi-mode fiber is used, 2 fibers are used (WDM is not normally used on multi-mode fiber). POF is a newer plastic-based cable which promises performance similar to glass cable on very short runs, but at a lower cost.
Multimode fiber gives you high bandwidth at high speeds (10 to 100MBS - Gigabit to 275m to 2km) over medium distances. Light waves are dispersed into numerous paths, or modes, as they travel through the cable's core typically 850 or 1300nm. Typical multimode fiber core diameters are 50, 62.5, and 100 micrometers. However, in long cable runs (greater than 3000 feet [914.4 meters), multiple paths of light can cause signal distortion at the receiving end, resulting in an unclear and incomplete data transmission so designers now call for single mode fiber in new applications using Gigabit and beyond.
There are 2 major differences one color code. single mode will be white or yellow. multimode will be black or tan. 2nd the hole in the connector ferrel for the fiber. fiber is 125 microns. in a single mode connector the opening is 126 microns. multimode is 127/128.
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The body needs a certain number of calories just to keep up regular bodily functions. It also needs calories to provide energy for the physical work you do each day. When you drastically cut calories, your metabolism slows down so not to use up the calories you do have. These calories are stored as fat so your body has an energy supply and keeps running. It's like if you knew your job was going to stop paying you, you'd slow down your spending and start saving. That's what your body does.
1) data-rate is not a limit imposed by the fiber, it depends on how good your receivers are.
1a) single mode fiber can also transmit multiple colors of light in parallel, the difference is that a multimode fiber has multiple paths for a single frequency (color) of light. Since these paths are of different length, the end result depends on how long your fiber is (thats dispersion). A receiver just measures the sum of all intensities.
2) Multimode fiber is just used with short cable lengths, so dispersion is not an issue. For example TOSLINK is a (very thick) multimode fiber used for digital audio. They even use a LED as a transmitter because they don't care about dispersion.
Multiple beams are also very expensive because you need multiple lasers with different colors, so you generally only use single-mode fiber of great length (like, transatlantic). For shorter lengths you use multiple cables.
3) Multimode fiber is almost never used these days. It is not just the quality, also the thickness of the fiber has to be an exact diameter (not too thick) or it will become multimode. In the past this was difficult, but now it has been perfected (and therefore cheaper).
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Actually the maximum data-rate IS limited in multimode.
When you inject a pulse of light down a MM fibre it will take multiple (hence the name multimode) paths through the fibre, as the length of the fibre increases the difference in transit time of these different paths causes a 'smearing' of the pulse, so even with a 'perfect' 100% sensitive receiver the time-smearing will limit the maximum distance for a given signal bandwidth.
MM fiber is cheaper primarily because it uses cheaper materials and manufacturing techniques and the connectors don't need to be as precise.
So to answer your questions:
1a) See previous answers. Different 'colours' of light are used when transmitting multiple streams, the separation in wavelengths between different colours can be very small (a few nM), so dozens of different coloured data-streams can be sent in 'parallel'. This is called WDM (wavelength division multiplexing).
2) See previous answers. MM is fine for short distances or when you don't need very high data rates, the main reason MM exists is the cost of the substantially lower connectors, the cheaper (sometimes non-existent) focusing optics in the transmitters and receivers.
3) Don't confuse WDM with the transmitting parallel signals of the same wavelength. SM fiber by definition can't be bigger than a certain size.
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No, the gentle won't mirror/refract properly interior the middle of the Fiber, and you will lose your sign, or have reflections back to the transmitting optics. single mode with single mode, multimode with multimode.
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