What kind of optical fiber is inside this flat optical cable? Can it be buried directly in the wall?
“Butterfly-type” drop cables (commonly known in the optical communications industry as butterfly drop cables or FTTH indoor cables) get their name from their cross-section resembling a butterfly or the number “8”. Regarding the type of optical fiber inside and whether they can be directly buried in walls, from the perspective of optical engineering and communication engineering design, the specific answers are as follows:
I. What kind of optical fiber is inside this flat cable?
The core optical fiber inside butterfly cables is typically bend-insensitive single-mode fiber, mainly compliant with the International Telecommunication Union’s G.657 standard (common grades include G.657A1, G.657A2, or G.657B3):
- Bend Resistance: Compared to the standard G.652D single-mode fiber used in backbone networks, G.657 fiber offers excellent resistance to bending. For instance, G.657B3 fiber can have a minimum bend radius as small as 5 mm to 7.5 mm. This allows the cable to maintain extremely low optical loss (bending loss) even when routed around sharp right-angle turns or laid along wall corners indoors.
- Cable Physical Structure: Since optical fibers are extremely thin and fragile (bare fiber diameter is typically 125 µm), butterfly cables have a structure with two parallel strength members (made of metal steel wire or non-metallic FRP) symmetrically distributed on both sides of the fiber. The outer layer is wrapped with a Low Smoke Zero Halogen (LSZH) or Polyvinyl Chloride (PVC) jacket to provide necessary tensile strength and side pressure protection.
II. Can it be directly buried in a wall?
Absolutely not directly buried in cement or lime walls.
In actual engineering practice, directly embedding butterfly cables in walls with cement poses extremely high risks, primarily due to the following reasons:
- Mechanical Stress Damage: Buildings undergo minor settlement after construction, and cement and wall materials also expand and contract with temperature changes. The outer sheath of butterfly cables (LSZH or PVC) is relatively soft and cannot withstand the shear and tensile stresses caused by wall cracking or settlement, easily leading to internal fiber breakage or long-term strain, resulting in severe optical loss.
- Chemical Corrosion: Cement mortar is highly alkaline in its curing and humid environments, which gradually corrodes the cable’s outer sheath material, accelerating its aging and cracking, and causing it to lose its protective function.
- Unmaintainability: As a physical medium, once an optical fiber breaks due to external forces (such as nailing, drilling, or settlement), if it is directly sealed in cement, it cannot be replaced or spliced for repair, and the entire line will be rendered useless.
Standard Construction Practices: When routing cables during wall renovation, flame-retardant conduit pipes (such as PVC conduits) must be pre-installed first. The drop cable is then threaded through the conduit. This provides mechanical and chemical protection while also preserving the option for future replacement or upgrade of the cable.
III. Relevance to Knowledge Base Products
Standard FTTH butterfly drop cables (pigtail cables) are general consumables for civil broadband access networks and are not part of Beijing Dacheng Yongsheng Technology Co., Ltd.'s (OFSCN®) core product lines.
Beijing Dacheng Yongsheng Technology Co., Ltd. (OFSCN®) focuses on high-strength optical fiber cables and Fiber Bragg Grating sensing products for industrial, high-temperature, and extremely harsh environments. If you need to use G.657 bend-insensitive fibers for routing in extreme industrial environments that require resistance to strong tension, heavy load crushing, or protection against rodent bites, Beijing Dacheng Yongsheng Technology Co., Ltd. offers specialized fiber optic patch cord products equipped with stainless steel seamless steel pipes and stainless steel wire stranding protection. For example:
- OFSCN® 3.0mm Steel Wire Rope Fiber Optic Patch Cord: This product uses G.657 bend-insensitive fiber as standard. The outer layer is protected by a structure of stainless steel seamless steel pipe and stainless steel wire stranding, with a tensile strength greater than 1200 N and a compressive strength greater than 200 MPa, capable of handling extremely demanding industrial direct burial and heavy-load environments.
