Fiber with three guiding layers: a doped single-mode or few-mode core, a large inner cladding often 125 to 400 µm across with a high NA around 0.46, and a low-index polymer or glass outer cladding. Bright but multimode pump diodes are launched into the inner cladding and absorbed gradually as their light crosses the core. Noncircular inner claddings, octagonal or D-shaped, stop pump rays from spiraling around and never hitting the core.
It's 20/400 double-clad fiber, so check the cladding absorption at 976 on the datasheet and cut the gain fiber length to match.
Pump light left in the cladding at the output end has to be stripped and dumped as heat before the splice or connector, or it cooks the coating.
Also heard as
- DCF
- double-clad
- cladding-pumped fiber
Related terms
Fiber laser
A laser whose gain medium is an optical fiber with a rare-earth-doped core, pumped by diodes.
Pump combiner
A fused fiber component that merges the outputs of many pump diodes into the inner cladding of a double-clad fiber.
LMA
Large Mode Area: fiber with an enlarged core that spreads light out to raise nonlinear and damage limits.
Pump
The energy source that excites a gain medium, or the act of supplying it, usually with diodes, flashlamps or current.