Single and Multi-mode in Fiber Optic Cable

Hello

What do you mean that Mode of Communication? I think that it is a cable specification.In a fiber optik cable,according to Signal sending angle; it is defined that which elektromagnetic signals can be sent.

That is,There are some elektromagnetic signal modes.(E00,E10,M11 etc.)

İn single mode,E00 wave can be transported.However in multimode more modes of wave can be transported.You can define that which modes are transported by make a number of process.

The modal behaviour depends on the kind of fiber (construction parameters such as materials, kind of construction, width of the core ....) and also depends on the wavelength the fiber is working on. A multimode fiber in the first window (850 nm) could work as single mode in the third window (1550nm).

In single mode only a mode(solution of the wave equation in the waveguide under study) is transmitted and in multimode many modes at the same time. Many modes usually is "bad".

To calculate your link first of all you have to know the requirements of the link (minimun binary rate and distance to cover) Then you have to choose the equipments(fiber, tx, rx) that satisfy the Power-Balance of the link and the disperssion balance.

Gustavo Sutil

gustavosutil (at) gmail.com

Multimode (M/M) fiber optic cable is typically listed as 62.5/125 where the 62.5 identifies the diameter in microns of the central fiber core (the part where the light actually goes through) of the cable and the 125 is the diameter in microns of the entire glass element within the cable. Single mode (S/M) fiber optic cable will have a specification of around 9/125 which indicates a central core of only 9 microns.

As a practical matter M/M cable is useful over distances of up to 1000 meters. It is possible to go longer distances with M/M cable but beyond this distance you start to run into problems. S/M cable is useful for much greater distances; 50 KM is not too much of a problem.

Other considerations are that S/M components such as connectors, NIC cards and other electronics are much more expensive than M/M components. It is also more difficult to make good connections with S/M than with M/M due to the small size of the central glass core. Interestingly enough the S/M fiber optic cable is slightly less expensive than a similar M/M cable.

Hello

Thanks for the reply.It means if i have multimode cable i can not use it for distance more than 1000mts. Also if the patch panel BLACK BOXES connectors are designed for mullti mode cables we can not connect single mode cable since the diameter of central core is different.Hope i am making some sense.pl.clarify

Chandrashekar NB

The tolerances for S/M cable are much tighter than for M/M cable. We have found that we can use S/M connectors and patch panels for M/M cables but not the reverse.

As noted previously it is possible to go further than 1000 Meters with M/M cable but not recommended. 3000 Meters is way too far to try a M/M fiber link.

50/125 is now popular for M/M fiber cable. 50/125 has a smaller core and focuses lightwaves tighter, resulting in 3X the bandwidth of 62.5/125.

Go here for a good explaination of fiber optic cable info and assembly photos

http://www.techcable.com/HTML/optical.htm

you can use mm cable for more than 1000 m but it depends on th binary rate you need. if the requirements aren't so big (in optic no big is 100Mbps or more) you can use mm. Also is important the attenuation of the fiber.

Gustavo Sutil

With multimode the signal is made up of several different wavelengths and these travel at slightly different speeds so by the end of 3kM you may find that the original binary bits have been all mixed up as the slower wavelengths lag far enough to interfear with the next bit. Single mode only transmit at one wavelength so the signal is pure when it reaches the other end giving you a much faster transmission speed. Another advantage of single mode is the ability to send several signals down one line at different wavelenghts then splitting them out at the other end. I'm not sure how far they got with this Agilent (Ipswich) were working on this right upto the point they closed us down.