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New Member

OC1/OC3/OC12/OC48/OC192

I understand that each of these OC levels have a different bandwidth, but how does the bandwidth increase? All of my web searches just define the data rate and do not explain how. A T1 line is 24 64kbps channels, a T3 is 28 T1's. Do the OC levels work in a similar manner?

3 REPLIES
Green

Re: OC1/OC3/OC12/OC48/OC192

Yes,they do.

An OC1 is roughly 50Mbps.OC3 is 155, OC12 is 622 (4 X OC3), OC48 is 2.4G (4 X OC12), OC192 is ~10Gig (4 X OC48).

(numbers rounded for simplification)

The hierarchy works well for upstream/downstream MUX/DEMUX, just like the DS0/T1/DS3 hierarchy.

FWIW

Scott

New Member

Re: OC1/OC3/OC12/OC48/OC192

Thanks for the info. Another question, physically the MMF fiber I have that connects my switches (3550's and 2950's) can operate at 100Mbps or at 1Gbps. I do not need to bundle a group of lines together to get it to operate at 1Gbps I use the same fiber strand. The speed is a matter of configuration on the ports. Is the fiber any thicker for an OC192 connection then an OC1? Could the same strand of fiber that is used to operate at OC1 (~50Mbps)speed also operate at OC12 speed (~622)? Or is their some physical limitation to the speed and therefore to get to the higher speeds the lines are grouped together?

Green

Re: OC1/OC3/OC12/OC48/OC192

No, actually, after OC12 (622Mbps) you'll see exclusively single-mode cabling. Single mode fiber is 8.3 micron "conductors", where multi-mode glass is usually either 62.5 micron or 50 micron.

The transmitters (and to some extent, the receivers) are the limiting factor.

Multimode generally uses an LED to generate the signal - which can only switch on and off so fast. The light is less coherent, and relys bascally on the light "bouncing" through the glass from wall-to-wall (/\/\/\/\/\/\/\/ ...).

Single mode transmitters are usually some flavor of laser/laser diode, which (may/usually) has a faster switching rate. The laser light is coherent (a single tight pencil of light) that is more like a direct, straight ine through the glass ( ======== ).

Up to OC12, either single or multimode fiber may be used, depending on the transmitter (the choice is usually a matter of the distance you need to cover - single mode / laser can achieve greater distances).

An organization may also implement single mode fiber as their inside plant to "future proof." GENERALLY SPEAKING, using single mode for shorter distances requires some sort of optical attenuator to reduce the signal strength (otherwise you may burn out the receiver or the receiver overloads and distorts the signal).

You can find devices that will do 10 Meg Ethernet over single mode, you can find devices that will do OC12 over multimode ... there are reasons for each ... but GENERALLY SPEAKING, Multi-Mode is used for indoor / local plants, and single mode is used for distance and extremely high speeds (regardless of the distance).

FWIW

Scott

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