
> 360 URLs

WELCOME
to
williamsonlabs.com
HOME

> 90 Subjects



Soliton P
l e

{As of ~ 1995}
There is a new fiber optic data transmission scheme that utilizes something
called Soliton Pulses. These are very
short bursts of light generated in an Erbiumdoped Fiber LASER. Soliton
light can be used to transmit data at rates in excess of 50 Gb/s, at distances
over 19,000 km of DispersionShifted Fiber, requiring no repeaters,
and with no errors. This data rate is the equivalent of sending 6,200 bibles
per second. At this rate, one bible could be sent to everyone on earth5.5
^{9}peoplein
about 10 days.
In the case of repeaters, in a longhaul fiber: instead of converting
the light into electrical signals, amplifying, correcting errors, retiming
and retransmitting light pulses, an optical amplifier is used. It consists
of about 30 meters of Erbiumdoped fiber, assorted filters and beam splitters,
and pumped by a 15 mW LASER diode operating at 1550 nm. This arrangement
adds about 30 dB of gain with no appreciable noise. Also, the bandwidth
of this amplifier is on the order of 40 THz. At this rate, one bible could
be sent to everyone on earth, 5.5 ^{9 }people, in about 18 minutes.
The Shortest LASER pulse, to date, is ~10 Femtoseconds (10 ^{15
}sec).
Light would travel 1/8th the thickness of a sheet of paper in that time.
10 Fsec is to one second as one second is to 3.2 million years. 
A Soliton Pulse is: a pulse
of lightof sufficient intensity and correct wavelength traveling down
a special nonlinear optical fiber known as, DispersionShifted Fiber,
is classified as a Soliton Pulse. This Soliton light pulse exhibits a unique
characteristic of getting shorternot longer, as conventional wisdom would
dictate. Due to the nonlinearly of the fiber in the presents of light
exceeding some quantum threshold of intensitythe leading edge of the
pulse is being overtaken by the faster trailing edge. That is, the leading
edge of the light is undergoing a Doppler
RedShift,
while the trailing edge is experiencing a
DopplerBlueShift.
The result of this effect is a shortening of the pulse duration, with a
corresponding increasing Peak Power.
As the pulse looses energy (joules) over distance, it increases in Peak
powerthus insuring itself's staying above the peak threshold of the fiber
needed for the phenomenon in the first place! 
..
The Dichotomy of Soliton Pulses in DispersionShifted Fiber


Starting Out
Midway
Destination

In normal Dispersive finite bandwidth media, the greater the Distance
traveled, there is a Spreading of the pulse width, i.e., Signal Bandwidth
is reduced (resulting in Intersymbol Interference).
However, the opposite is true with Soliton pulses in DispersionShifted
Fiber. As can be seen in the above figure, the leading edge of the
light pulse is undergoing a Doppler RedShift,
while the trailing edge is experiencing a Doppler BlueShift,
narrowing the pulse; which Spreads the Bandwidth and Increases the Peak
Power.
Even though Average Power is Decreasing, the narrowing pulse forces
the Peak Power to Increaseassuring the continued operation in the Nonlinear
region of the DispersionShifted Fiber.

..
Conventional Fiber Communications
1.7 GBit/sec


[Light to Electronic] [Electronic to Light] (1800cu ft.)
Repeaters spaced ~ 20 km

..

Soliton Pulses in
DispersionShifted Fiber Communications, 25 Gbit/sec
< 19,000 km >
With No Errors


Optical/Light Amplifier Repeaters (0.5cu ft.) spaced ~ 30
km  100 km

..

> 50 Gbit/sec No Repeaters
Needed
< 19,000 km >
With No Errors


No Repeaters Needed

..
..
..

Distance Traveled

Time


Millisecond
1 ^{ 3 }= 1 msec 
300 km
186.4 miles 
is to one second as one second is to:

16.6 Minutes 
Microsecond
1 ^{ 6 }= 1 µ sec 
300 m
984.25 feet 
is to one second as one second is to:

11.574 Days 
Nanosecond
1 ^{ 9 }= 1 nsec 
300 mm
11.8 inches 
is to one second as one second is to:

31.7 Years 
Picosecond
1 ^{12 }= 1 psec 
300µ
12/1000 inches 
is to one second as one second is to:

31,688 Years 
Femtosecond
1 ^{15 }= 1 fsec 
300 nm
12/1,000,000 inches
Thickness of 1 sheet of paper
divided into ~ 130 parts 
is to one second as one second is to:

31,688,000 Years 
..
Velocity of Light in:
Free
Space =
Water
=
Quartz
=
Glass
~
Diamond
=


186,282
miles/sec
140,000
miles/sec
110,000
miles/sec
122,000
miles/sec
77,000
miles/sec 
Velocity of Sound in Air:
at
sea level @ 32°F (0°C) =
at
sea level @ 72°F (25°C) =

1,088 ft/sec; 337.28
m/sec = 742 MPH
1,136 ft/sec; 352.16
m/sec = 775 MPH 
Velocity of Sound in Water:
@
32°F (0°C)=

4,938 ft/sec;
1,530.78 m/sec = 3,366 MPH 
Velocity of Sound in Glass: 
18,046 ft/sec;
5,594.26 m/sec = 12,307 MPH 
..
~Doppler
Shift
~

Frequency Shift per
1 MPH of Velocity

F_{beat}
= 89.4 (V/wl)
fr/ft = 1(V/C)
where:
V = MPH
C = Light Velocity in MPH
F_{beat} = in Hz
wl = in cm (Wavelength)
C = 186,282.397 miles/sec
C = 299,792,458 meters/sec
1 meter = 39.37 inches 
© 1999  2011
Questions or Comments about this site webmaster
Suggestions are Solicited, P l e a s e !

