Fused Silica core
optical fibers are capable of conducting very high laser energy
under cw, average power and pulsed power levels. The actual
allowable maximum energies are dependant on:
- Fiber
Quality
Fused Silica (SiO2) with lowest contaminants has the highest
power handling capabilities
- Fiber face
polishing at both the input and the output ends
The polishing procedure must ensure that there are not any
sub-surface flaws remaining from the grinding and polishing
of the fiber ends. The final polishing step should use
polishing particles that are a small fraction of the
operating wavelength such as 0.1µm.
- Laser
wavelength, intensity level and mode distribution
The damage threshold of the fibers is less at shorter
wavelengths.
- Fiber
mounting
Fiber mounting at both the input and output should use
thermally resistant buffers and epoxies to handle any
thermal biuld up.
- Cleanliness
conditions
Dust particles on the fiber face introduce hot-spots that
may lead to catastrophic failures.
- Fiber core
diameter
Power handling is proportional to core area, ie diameter
squared. Maximum cw power handling is usually constrained by
thermal consideration. With good polishing, alignment, and
cleanliness conditions cw powers should be limited to about
126kW/cm2 at wavelengths of greater than 500 nm. Under very
carefully controlled conditions including special cooling
these levels can be increased by a factor of 3- 3.5.
|
Fiber Core/CW Power
Limitation
|
FIBER CORE DIAMETER
(µm)
|
CW POWER LIMITATION
(watts)
|
|
|
50
|
|
2.0
|
|
|
100
|
|
8.0
|
|
|
200
|
|
32
|
|
|
400
|
|
128
|
|
|
600
|
|
288
|
|
|
1000
|
|
800
|
|
 High-power
laser transmission cables |
