Multimode couplers are manufactured using a technique or fusion technique. They are available for all common multimode fibres with core diametres from 50 µm to 1500 µm.

Fusion and taper couplers offer different advantages. They are used for signal division and signal combination.

Fusion couplers' mode-sensitivity of the coupling ratio can couse problems in certain applications.

When coupling conditions alter, the ratio of the coupler may also change, for example a 50/50 coupler may become a 75/25 coupler.

The taper coupler from SEDI is a mode-insensitive, wavelength-independent alternative to fusion couplers. The coupling ratio remains virtually unchanged, even with varying coupling conditions. Another important advantage of a taper coupler is its absolute wavelength independence.

Manufacturing of taper couplers

When manufacturing a taper coupler with a splitting ratio of 50/50, the ends of the two fibres are first beveled to a specified angle equal to half of the fibre diametre and then polished. The two fibres are glued to a third fibre, forming a Y-shape.

The mode field of the input signal is effectively split down the middle. Thus, the coupler ratio for all modes is practically the same. Other division ratios can be achieved by simply varying the polish section angle of the fibres.

Areas of Application for Taper Couplers

The main areas of application for taper couplers are the so-called "large core” fibres. These are step index fibres with a core diametre of 200 µm – 1000 µm. The couplers can be supplied in various designs and assembled for use with all common connectors. They are available for all common multi-smode fibres with core diametres ranging from 50 µm to 1500 µm.