- Fiber Optics
- Fiber Connectby Technology Explained Date Added: Thursday 23 February, 2012Compared to single mode optical fiber, multimode optical fiber has following feature:
The core diameter of the fiber is much larger. This means multiple transmission modes are permitted in the fiber at the wavelength of the light.
A larger fiber core means larger numerical aperture (NA). So multimode fiber can accept light from wider incident angle. This makes it easier to couple light into the fiber. Hence the cost of optical transmitters for multimode fiber links is lower. Typical wavelengths used in such link are 850nm and 1310nm. Low cost laser diodes at those wavelengths, or even low cost LEDs (light emitting diodes), can be used as light source.
Because of multiple transmission modes, there is a limit caused by mode dispersion on the maximum signal bandwidth and transmission distance product achievable for the multimode fiber. Mode dispersion is that different transmission mode has different propagation constant inside the fiber. Optical pulse is broadened by mode dispersion along the fiber. The longer the transmission distance, more severe the broadening on the optical pulse becomes.
The limit from mode dispersion restricts the application of multimode fiber to short reach networks, such as 2km for 100Mb Ethernet link, or 550m for 1Gb Ethernet. Multimode fibers are mostly used in high speed point-to-point connections within a single building or a small campus.
Currently, higher bit-rate multimode fiber transceivers are developed, for example 10Gb transceivers. Although the transmission distance is further shortened at such bit-rate, multimode fiber can play a role at high speed backbone networks.Rating: [5 of 5 Stars!]
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- Fiber Optics