**3.5 Splicing of plastic optical fibres**

Fusion splicing of plastic optical fibres (POF) made of poly-methyl-methacrylate (PMMA) or TOPAS polymer is very hard. For example, the tip of microstructured fibre made of PMMA forms a cone when heated, instead of rounding typical for fused silica fibre (Figure 10).

Filament splicing and split-mould fusion of POF were reported, but failed to find acceptance. Butt-coupling is adopted for large diameter (up to 1 mm) solid POFs used in car, aircraft and industrial networks, and gluing is used as well. Microstructured plastic optical fibre (mPOF) can be glued, also to glass fibre (Bang, 2010). Polymer fibres are cleaved by cutting with razor blade at controlled speed. Blade and fibre must be heated; the temperature range for PMMA fibres is 60-90C (Law et al., 2006).

Fig. 8. Sharp bend of SMF observed with OTDR at 1310 nm (left) and 1550 nm (right).

introduction of short fibre with intermediate MFD, as shown in Figure 9.

Fig. 9. Principle of splicing through intermediate fibre.

temperature range for PMMA fibres is 60-90C (Law et al., 2006).

**3.5 Splicing of plastic optical fibres** 

MFDA

If fibres having substantially different MFD must be spliced, loss can be reduced by

**(a) Direct splicing** 

MFDA MFDB

Fibre A Fibre B

**(b) Splicing through intermediate fibre**

MFDI MFDB

**MFDA MFDI MFDB** 

Fibre A Fibre B

Intermediate fibre

Fusion splicing of plastic optical fibres (POF) made of poly-methyl-methacrylate (PMMA) or TOPAS polymer is very hard. For example, the tip of microstructured fibre made of PMMA forms a cone when heated, instead of rounding typical for fused silica fibre (Figure 10).

Filament splicing and split-mould fusion of POF were reported, but failed to find acceptance. Butt-coupling is adopted for large diameter (up to 1 mm) solid POFs used in car, aircraft and industrial networks, and gluing is used as well. Microstructured plastic optical fibre (mPOF) can be glued, also to glass fibre (Bang, 2010). Polymer fibres are cleaved by cutting with razor blade at controlled speed. Blade and fibre must be heated; the

Fig. 10. Deformation of fibre tips by heat of electric arc: DTU MIK125/0.5 made of PMMA (left) and Corning SMF-28 made of fused silica (right). Top: cleaved fibres, middle: after 1st heating, bottom: after 2nd heating.

Handling and splicing of thin mPOF with standard equipment is difficult due to softness of polymers in comparison to fused silica. In experiments at NIT, mPOF of 125 μm diameter exhibited unacceptable sag and curl when clamped 4 mm away from tip, while standard V-groove clamps usually damaged the fibre.
