If there is no selection standard for empty racks under the outdoor optical cable laying standard and the laying distance is far, direct burial laying is widely used, and direct burial laying should meet the following requirements:

Avoid areas with strong acid and alkali corrosion or severe chemical corrosion; when there is no corresponding protective measures, prevent termite damage areas and areas that are easily damaged by pyrogens or external forces.

The optical cable should be laid in the trench, and the periphery of the optical cable should be covered with a soft base treatment or sand layer with a thickness of not less than 100 mm.

Along the total length of the optical cable, a protective plate with a total width of not less than 50 mm on both sides of the optical cable should be covered, and the protective plate should be made of concrete.

In areas where foundation pits are frequently excavated, such as urban and rural paths, at the laying site, a conspicuous marking tape can be laid on the top layer of the protection board.

Located on the outskirts of the city or at the laying part of the wide belt, at the distance of about 100 mm between parallel lines along the path of the optical cable, at the corners or at the joint positions, prominent direction signs or signposts should be erected.

When laying in the non-frozen soil area, the optical cable skin to the underground building should not be less than 0.3m, and the optical cable skin to the road depth should not be less than 0.7m; when it is located in the motorway or agricultural underground, it should be as heavy as possible, and it is not suitable for less than 1m.

When laying the outdoor optical cable in the permafrost area, it should be buried below the permafrost. When it cannot be buried, it can be laid in dry frozen soil or backfill with good water permeability, or other measures to prevent damage to the optical cable can be adopted. When the optical cable route laid by direct burial intersects with railway lines, roads or sub-district offices, maintenance pipes shall be worn, and the protection standard shall exceed the subgrade, the two sides of sub-district office grounds and the side of sewage ditch by more than 0.5m.