What is a "mechanical splice"?

OFSCN Global Technical Center OFSCN Technical Knowledge Base
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When there is no power in the field, how can I quickly reconnect a broken optical fiber?

2

In situations where no external power is available in the field and a Fusion Splicer cannot be used, the quickest and most reliable fiber optic emergency connection solution in optical engineering is Mechanical Splice.

I. Working Principle of Mechanical Splice

Mechanical splicing is a technology that achieves fiber optic connection entirely through precise mechanical alignment and physical crimping. Its core principles include:

  1. Precision Mechanical Alignment:
    The interior of a mechanical splice connector typically features a micro V-groove manufactured with extremely high precision. By inserting two fibers, stripped and cleaved at their ends, into the groove, the V-groove geometry constrains and aligns the cores of the two fibers with micrometer-level accuracy.

  2. Index-Matching Gel:
    Unlike fusion splicing, mechanical splicing cannot eliminate the physical interface between the fiber ends. To prevent strong Fresnel reflection and loss caused by the air gap (refractive index of air n \approx 1.0) between the two end faces, the mechanical splice connector is pre-filled with an index-matching gel whose refractive index is very close to that of the silica fiber core (n \approx 1.46). This allows the optical signal to pass smoothly across the connector interface.

  3. Mechanical Locking:
    Once the fibers are inserted, they are mechanically secured by the connector’s integrated crimp clip, slider, or a specialized cold connection tool. This locks the fiber’s coating and bare fiber, maintaining connection stability.

II. Field Emergency Operation Steps (Requires only passive manual tools)

  1. Strip Protective Layers：Use fiber optic strippers to remove the outer jacket and the 250\ \mu\text{m} coating of the fiber, exposing the bare fiber.
  2. Clean：Use lint-free wipes moistened with anhydrous ethanol to clean the surface of the bare fiber.
  3. High-Precision Cleaving：Use a portable Fiber Cleaver to create a flat 90^\circ perpendicular end face (the flatness of the end face directly determines cold splice loss and return loss).
  4. Insert and Crimp：Insert the ends of the fibers into the mechanical splice connector respectively. Observe the micro-bending of the fibers to confirm end face contact, then press down the locking cover/clip to complete the fixation.

III. Technical Characteristics and Precautions

  • Insertion Loss：The typical insertion loss for conventional single-mode fiber mechanical cold splices is approximately 0.1\ \text{dB} \sim 0.3\ \text{dB}.
  • Environmental Tolerance：The index-matching gel inside may degrade or volatilize in extreme high/low temperatures or dusty/humid environments. Therefore, field cold splicing is often used for emergency repairs or temporary testing. When conditions permit, it is usually recommended to ultimately replace important sensing backbone links with arc fusion splicing or armored pre-terminated fiber optic cables.

(Note: Standard general-purpose fiber optic cold splice connectors/mechanical splice accessories are common fiber optic communication construction tools and do not belong to Beijing Dacheng Yongsheng Technology Co., Ltd.'s OFSCN® core series of fiber Bragg grating sensors and metal-encapsulated devices.)