European equivilents of T1/T3. 

E1 - 2.048mb/s

E3 - 34.386mb/s

Not compatible with T* (or J*). 

Fiber Optics

To Curb: Service ends at the telephone pole 

To Desktop: Service ends at the user's computer

Bright red/orange wires: Fiber optics.

Started out prorietary and not intercompliable.

AT&T's split prompted a standard emergence.

Syncronous Digital Heirarchy: US calls it Syncronous Optical NETwork.

Fiber Optic Service Levels (like T*).

  • STS1 only exists in NA. 51.84mbits/s
  • STS3. 155.52mbits/s
  • ... 
  • STS768 (aka STM256) 40gbits/s
  • Number is a direct multipler (number of pipes).

STS1 frames are 90*9 bytes.

Sections of a frame: Section Overhead, Line Overhead, Payload.

A section is the length of fiber between two repeaters/terminals/switches.

A line is the length of fiber between two terminals/switches.

A path is the length of fiber between two terminals.

Path overhead is small by compasison to section/line.

Overhead on frame is small compared to payload, efficient in that regard.

Path overhead is inside the payload, 9 bytes big.

Non-concatinating frames on larger pipes scale the size of the frame.

If you use STS3c frames, they are STS1 size but only every 3 frames needs overhead.  If they are bound for the same destination the other frames can be pure payload.

Transforming metal carriers into optical

T3 is 45mbits/s, close to STS1.  What if you need to transport multiple T1s < 45mbits/s?

You need to operate using inflexible virtual tributaries: logical units used to carry T1 signals over optical.

VT1+1/2: 1.128mbits/s

VTG: Virtual Tributary Group

All tributaties in the group need to be the same capacity.

Fiber Topology 

Laying fiber: $75,000-$250,000 per mile

Mesh topology is too expensive, star is too fragile, ring is good.  Interlocking rings are even better.

Multiplexing 

Frequencing Division Multiplexing, oldest type.

Fiber uses Wavelength Division Multiplexing (color).  Laser can produce a pefect wavelength.  Used on single mode fiber. 4-16 colors can be used (or even more).

Elias Dope Amplifier (not regenerator).  Shorter wavelengths will bleed enegery into longer ones.  So induce a really short one that isn't used for data.  Works best on fiber doped with urbium.

On fiber optics noise is minimal.