- 2079 Chaitra · 3 marks
Short note: Splicing
Short answer
Splicing permanently joins two optical fibres. Fusion splicing melts fibre ends with an electric arc (loss ~0.02–0.1 dB), while mechanical splicing aligns ends using a V-groove and index-matching gel (loss ~0.1–0.5 dB). Loss sources include misalignment and Fresnel reflections.
Write a short note on splicing.
Splicing is the permanent (or semi-permanent) joining of two optical fibres end to end so that light passes from one to the other with minimum loss. It is needed because cables come in limited lengths (2–6 km) and for repairs.
Types of splicing
- Fusion splicing: the cleaned and cleaved fibre ends are aligned (often automatically using cameras) and fused by an electric arc, so the glass melts into one piece.
- Loss: about 0.02–0.1 dB; very low back-reflection; strong and stable.
- Needs an expensive fusion splicer; used in backbone and long-haul links.
- Mechanical splicing: fibre ends are held in alignment by a mechanical structure such as a V-groove, an elastomeric splice or a precision tube, with index-matching gel to reduce reflection.
- Loss: about 0.1–0.5 dB; quick, cheap tools; used for field repairs and drops.
Causes of splice loss
- Extrinsic: lateral (offset) misalignment, longitudinal gap, angular tilt, poor end-face cleave.
- Intrinsic: mismatch in core diameter, NA, index profile or core ellipticity between the two fibres.
- Fresnel reflection at a glass–air gap (≈ 0.17 dB per surface) in mechanical joints without gel.
Splices are protected with heat-shrink sleeves and kept in splice trays inside joint closures.
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