Also known as a pump coupler, the pump combiner is an optical passive component that is used for sending pump and signal light into an amplifier or laser fiber. As pump combiners are used in varied applications, they are specially designed for high-power use. The high power of the combiner makes its use easy and quick in different industries.

The design of the pump combiners is based on the Fused Biconical Taper (FBT) technique. This means several pump fibers are arranged around a signal fiber and the whole bundle that is typically surrounded by a glass tube is tapered down in a way, aligning perfectly with that of the active fiber.

All pump combiners are not the same. They are structurally different, helping in different industries. The different constructions of a pump combiner are:

Multimode pump combiner

As the name suggests, the multimode pump combiner couples 7 or 19 multimode sources into a cladding-pumped fiber. The combination of the optical power with different optical fibers creates a high power output.

The multimode pump combiners are used in industrial, military, and medical industries. Other than this, the multimode combiner facilitates highly efficient power transfer, catering to the needs of high-power applications. The high power applications include direct diode material processing and pump cascading, ensuring maximum brightness conservation.

The multimode pump combiners are available in different configurations, which are used in different applications.

Single-mode combiner

Opposite to multimode pump combiner, the single combiners couple 6 or 18 multimode sources and 1 single-mode signal source for combined power output or use with a cladding power. Though a single-mode combiner has certain limitations, it is used in different applications because of the “Signal fiber design”.

The single-mode pump combiner is used in industrial, military, and medical industries like the multimode pump combiner. Other than this, the single-mode combiner is used to construct an amplifier for use in telecommunications.

Polarization maintaining combiner

Completely different from multimode and single-mode pump combiners, the polarization-maintaining combiner couples 6 multimode sources and 1 polarization-maintaining source for combined power output or use with a PM cladding-pumped fiber. The polarization-maintaining combiner possesses polarization-maintaining properties for signal use only.

Even here, the “Signal fiber design” comes into the picture. The design is used to construct amplifiers requiring signal polarization outputs, which are used in industrial, military, medical, and telecommunication industries.

What are the different configurations of multimode, single, and PM pump combiners?

Nx1 multimode combiners

  • 19×1 multimode combiner
  • 7×1 multimode combiner
  • 4×1 multimode combiner
  • 3×1 multimode combiner
  • 2×1 multimode combiner

(N+1) x1 single combiners

  • (18+1)x1 single combiner
  • 1.5um (6+1)x1 single combiner
  • 2.0um (6+1)x1 single combiner
  • 1.0um (6+1)x1 single combiner
  • 1.5um (2+1)x1 single combiner
  • 1.0um (2+1)x1 single combiner
  • 2.0um (2+1)x1 single combiner

Polarization maintaining combines

  • 5um (6+1)x1 PM combiner
  • 2.0um (6+1)x1 PM combiner
  • 1.0um (6+1)x1 PM combiner
  • 1.5um (2+1)x1 PM combiner
  • 1.0um (2+1)x1 PM combiner
  • 2.0um (2+1)x1 PM combiner

The use of different pump combiner constructions varies from industry to industry. So, choose wisely.