Center Tube Micro Air blown Fiber Optic cable

Center tube (CT) design has all fibers in a single central tube — it is more compact, has higher fiber density per cable cross-section, and offers greater blowing distance due to its symmetrical, low-friction profile. Stranded loose tube (SZ) design has multiple smaller tubes stranded around a central strength member — it scales to higher fiber counts (288+ cores) more economically. ZTO center tube cables are typically used for access network and FTTH up to 144 cores, while stranded designs are preferred for backbone applications requiring 288–576 cores.

Center tube design supports 12, 24, 36, 48, 96, 144, 192, and 288 cores. For 12–144 cores the cable diameter is in the 5.5–8.5 mm range (fits 10/12 or 12/14 mm micro-ducts). For 192–288 cores, diameter increases to 9–11 mm and may require 14/16 mm micro-ducts. For projects requiring more than 288 cores, ZTO recommends switching to stranded loose tube design for better cost-efficiency and duct fill ratio.

The grooved sheath (also called ribbed or profiled sheath) reduces surface friction between the cable and the micro-duct inner wall during air-blown installation. This extends maximum blowing distance by 30–50% compared to smooth-sheath designs at the same air pressure. The grooves also distribute air pressure more evenly around the cable circumference, improving blowing stability over multi-bend routes. The trade-off is slightly higher cost and a marginally larger outer diameter, but for access networks with long or curved duct runs the performance gain is significant.

Standard options include G.652D (standard single-mode, lowest cost), G.657A1 (bend-insensitive, 15mm bend radius), G.657A2 (extra bend-insensitive, 7.5mm bend radius, ideal for indoor transitions), and multimode OM3/OM4 for short-reach data center and enterprise applications. For FTTH access networks, G.657A2 is most common because it allows tight bends during indoor drop installation. For long-haul or high-speed applications, G.652D is standard. The fiber type can be mixed within a single cable on request.

In optimal conditions (straight duct, low friction), single-blow distances of 1,500–2,500 m are achievable. For typical access network routes with multiple 90° bends, expect 800–1,500 m per blow. Routes with multiple 180° bends typically achieve 400–800 m. Actual distance depends on duct quality, number of bends, blowing equipment pressure (typically 8–12 bar), cable lubricant pre-treatment, and ambient temperature. ZTO can provide duct-route-specific distance estimates based on your project survey data.