How does blown fiber work?

Microducts (5-14 mm OD) are installed during initial construction. When fiber is needed, a blowing machine feeds micro-cable (1-4 mm diameter) into the duct while compressed air (8-15 bar) propels it at 30-100 m/min. Air drag on the cable's outer surface provides distributed force, avoiding the tension limits of pulling. Distances up to 2,000 m are achievable in one blow.

Advantages over traditional pulling?

Future-proof: install ducts once, blow fiber when needed. Upgradeable: remove old fiber, blow new (higher count or bend-insensitive). Lower force: distributed air drag vs concentrated pulling tension. Faster: 2,000 m in 20-30 minutes vs hours for pulling. Risk reduction: fiber installed after civil works, avoiding construction damage.

Fiber count and distance?

Micro-cables range from 1 fiber (2 mm cable) to 288 fibers (8 mm cable). Blowing distance depends on duct ID, cable OD, bends, and air pressure. Typical: 1,000-2,000 m in straight/gentle routes. Tight bends and vertical runs reduce distance. Multiple ducts in a single outer duct (multi-duct bundles) allow independent fiber routes.

Fiber & Cable Systems

Blown Fiber

Blown Fiber is a fiber optic installation technique where micro-cables (1-8 mm diameter) are pneumatically propelled through pre-installed microducts (5-14 mm OD) using compressed air at 8-15 bar. Air drag on the cable surface provides distributed propulsion, avoiding the tension limits of traditional pulling methods. Installation speeds reach 30-100 m/min over distances up to 2,000 m, enabling rapid deployment and future-proof FTTX infrastructure where fiber can be upgraded without replacing ductwork.

Category: Fiber & Cable Systems

Speed: 30-100 m/min

Understanding Blown Fiber

The key innovation is separating duct installation from fiber deployment. Microducts are installed during civil works (trenching, boring). Fiber is blown only when service is needed, potentially years later. This "just-in-time" deployment reduces upfront fiber costs and allows technology upgrades (e.g., replacing OM3 with OM5 multimode, or adding fibers to meet growing demand).

The blowing machine grips the cable and feeds it into the duct at controlled speed while a compressor provides air flow. The air creates viscous drag along the cable's entire length, distributing the installation force evenly. This is gentler than pulling, where all force concentrates at the cable's leading end.

Installation Parameters

Air pressure: 8-15 bar
Speed: 30-100 m/min
Max distance: 1,000-2,000 m (route dependent)

Fill ratio (cable OD/duct ID):
Optimal: 50-60% for single cable
Max: 70% (higher friction limits distance)

Blown vs Pulled Fiber

Parameter	Blown Fiber	Pulled Fiber
Force distribution	Distributed (air drag)	Concentrated (pull point)
Distance/run	Up to 2,000 m	Up to 3,000 m
Speed	30-100 m/min	10-30 m/min
Upgradeable	Yes (blow out/in)	Limited
Duct required	Microduct (5-14 mm)	Standard duct (25+ mm)

Common Questions

Frequently Asked Questions

How does it work?

Compressed air (8-15 bar) propels micro-cable through microducts at 30-100 m/min. Distributed drag avoids tension limits. Up to 2,000 m per blow.

Advantages?

Future-proof ducts, upgradeable fiber, faster install, lower force/risk. Deploy fiber only when service is needed.

Fiber count?

1 to 288 fibers per micro-cable. Multiple microducts in bundle ducts allow independent routes. Distance depends on bends and duct fill ratio.

Related Terms

← Blocking Switch BLT Equation →

Fiber Infrastructure

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