Abstract

Today’s installed Local Area Networks (LAN) cabling systems are structured cabling systems using symmetrical twisted-pair copper cables (Cat. 5/6/7). These cabling systems provide 10 to 100Mbit/s data transmission rates over connection distances up to 100m. New information technology (IT) developments, such as digitising of pictures including movies, three-dimensional computer added design systems (3D-CAD), and the implementation of client server-based business critical applications, require new high-performance personal computing systems. The interconnection of these PC’s requires new LAN cabling systems providing 1 to 10Gbit/s (Gigabit-Ethernet) data transmission rates according to the implementation standard IEEE 802.3, into the foreseeable future.

Introduction

The use of optical fibres for the implementation of LAN cabling systems for 1 to 10Gbit/s data transmission rates offers some unique features compared with copper cabling systems. Optical fibres are uncritical in terms of the interference of neighbour data transmission lines at high-transmission rates. They also offer an excellent bandwidth (Figure 1).

Figure 1: Bandwidth comparison of glass fibre, polymer fibre, copper cable

For cabling systems in wide area networks (WAN), the use of single-mode optical fibres (SMF) is already a well-established technology. The requirements of optical LAN cabling systems are different from those of cabling systems used for wide area networks. Typical transmission distances in WAN cabling systems are 10 to 100km. Synchronous optical networks (SONET) for WAN’s using dense wavelength division multiplexing (DWDM) technology require lower fibre counts than metropolitan (MAN) or local area networks (LAN). Also, transmission distances in LAN’s are much shorter than the distances in WAN’s. Cabling systems for covering distances of approximately 10 to 500m fulfil the requirements of such indoor cabling systems.

Historically, the fibre design for indoor applications was different from those for outdoor applications. The use of multimode fibres (MMF) for LAN cabling systems also allowed the use of light sources other than lasers for launching the transmission signals into the fibre (Figure 2).

Figure 2: Vertical Cavity Surface Emitting Laser and LED light source for launching MMF

Several developments in both laser and single-mode fibre technologies now permit the implementation of high-performance communication systems for LAN applications, with acceptable investment costs.

Cable Construction

All types of indoor cabling systems (plenum and riser cables) must conform to some general design rules in terms of:

• Cable flexibility and strength;
• Compact design for easy handling;
• Flame-retardant insulation materials;
• Reduced termination costs.

Additional requirements of optical fibre cabling systems include:

• Prevention of stress corrosion of the optical fibre;
• Implementation of cable design parameters to avoid fibre micro- and macro-bending;
• Superior mechanical and moisture protection without the use of soft water-blocking materials (dry cable construction);
• Scaled fibre count cables according to their provision.

Typical fibre optical indoor cable designs taking account of these design criteria are:

a) Simplex patch cord cable (Figure 3);
b) Duplex patch cord cable (Figure 4);
c) Distribution cable (Figure 5);
d) Break-out cable (Figure 6).

Today’s typical production speeds for these types of cable are between 40 to 400m/min.

Figures 3 and 4: Simplex and duplex (Zipcord) cables

Figure 5: Distribution cable

Figure 6: Break-out cable

New cable characteristics and production methods promote the design of cable constructions without central members (Figure 7).

Figure 7: Compact distribution cable

All these cable designs derive from a basis of tight or semi-tight buffered fibres. Typically a fibre of 250µm will be coated up to 600 or 900µm, with the use of modified PA12, PVC, or flame-retardant polymers. The optional application of two coating layers (a low-modulus layer for protection of the fibre, in combination with a higher-modulus layer for environment protection) offers cable design variations (Figure 8).

Figure 8: Semi-tight buffered fibre

1. Flexibility
For high-productivity, various cable designs require a combined (tandemized) SZ-stranding extrusion technology. For production flexibility, and the realisation of optimal value from each individual step of the process, every element of the production line must be custom-designed. Rosendahl has achieved high-speed production performance with a variety of cable designs (Table I).

Table I: Line speeds of different product designs

High-production speeds require the latest technology: properly designed process equipment, a high-dynamic fibre pay-off, low-friction cooling systems, and a universal automatic dual take-up in combination with the adaptive line control system RIO.

2. Productivity
To offer solutions which increase the overall equipment efficiency (OEE) of the buffering line, Rosendahl has developed an active fibre launching system for continuous production.

2.1. Automatic fibre launching and fibre changeover at production speeds
Continuous improvement is essential if the cable manufacturing industries are to maintain optimum productivity. To ensure this, ever-higher levels of automation are necessary. From the concept stage onward, the designers of a modern buffering line must strive for significant improvements in velocity, flexibility, and ease-of-use of the new automated equipment. Rosendahl has succeeded in improving line productivity with implementation of its ChiB® fibre launching system in combination with a fibre clamping and cutting device.

Automatic launching protects operators from contamination, lacerations, splinters, and other hazards. The ChiB system is intended for automatic launching of one to twelve fibres into the crosshead of the extrusion line. Named for a Rosendahl process engineer who demonstrated how to launch fibres at 500m/min, ChiB (Charley-in-a-Box) technology was developed by Rosendahl’s R&D staff to replace existing passive automation systems and processes (Figure 9).

Figure 9: The ChiB active fibre launching system

2.2. Launching during start-up; scrap reduction
Up to twelve fibres can be launched automatically at production speed into the line (Figure 10). Table II shows the production advantages of ChiB.

Figure 10: Production with/without automatic fibre launcher and cutter

Table II: Semi tight coating, 400m/min line speed, 2.2km fibre length

Use of the ChiB fibre launcher ensures continuous operation, reduced scrap, and greater operator safety during the buffering process. For continuous operation, the machine is designed to be reloaded during production. The system remains in ready-to-go mode until the next launching. A ChiB fibre launcher is available for simplex, loose-tube, tight coating, and semi-tight coating production lines (Figure 11).

Figure 11: Fibre clamping and cutting device

2.3. High-dynamic fibre payoffs
Rosendahl’s ChiB fibre launching system and fibre cutting and clamping device work in combination with either the high-dynamic pneumatically loaded compact fibre pay-off MFA300 or the high-speed fibre pay-off MFA500 (Figure 12).

Figure 12: Multi-fibre payoff MFA300 and MFA500

The multi-fibre MFA300 is the compact pay-off system for high-end fibre optic cable manufacture using standard reels. Up to 24 in-line pay-off positions are possible, enabling the paying-off of up to 12 fibres while another 12 reels are being set-up. This is the basis for meeting the requirements of continuous production of up to twelve fibre tube designs. The MFA300 is intended for production speeds up to 500m/min; the fibre tension can be adjusted in the range of 30 to 300g with an accuracy of ±10% of the actual set-point. The multi-fibre pay-off MFA500 is designed for speeds up to 1,000m/min, and will support bigger reel sizes up to 500mm as well as varied product designs (fibre, tight-buffered fibre, HCS, POF, simplex, ribbon).

2.4. Lay plate SZ-strander
The patented Rosendahl non-linear driven lay plate SZ-stranding machine (Figure 13) ensures high-dynamic reversals (less than 30m/sec at ±2,000rpm) by absorbing the energy during “S” or “Z” stranding inside the rubbers. The combination of a balanced lay plate/stranding head design for premises cable production, directly connected with the extrusion process, ensures excellent premises cable quality combined with high productivity.

Figure 13: Lay plate SZ-stranding machine geared for 2,000rpm

2.5. Universal fibre optical cable
Rosendahl’s universal semi or full automatic dual reeler DSL1001 meets various cable design requirements in fibre optic cable production (Figure 14). The unit is geared for 1,250m/min, reel sizes from 250mm, and flange diameters up to 1,066mm. It covers product dimensions from 0.6 to 18mm outside diameter, including products having aramid yarns as strength members.

Figure 14: Universal automatic dual reeler DSL1001

Employed in combination, Rosendahl’s RIO line control system, its ChiB automatic fibre launching system for joining fibres, and the DSL 1001 automatic dual take-up dramatically increase production capacity, reduce quality variations, and decrease the scrap rate lower than previously achievable.

Conclusion

Based on more than a decade’s experience of responding to the demands of its customers around the globe, over the past three years Rosendahl has developed an exceptional extrusion and stranding technology. The company is able to offer to the market high-productivity manufacturing systems, correctly sized and customised for a wide product range of fibre optic cable designs. For the developments described in this article, Rosendahl’s goal was in every instance the enhancement of overall equipment efficiency (OEE) through improvements in design and production processes.

References

• IEC 60794 1-4: Optical Fibre Cables - Generic Specification and Test Procedures, 2001.
• Rödder, Thomas: “LWL Kabel für Öffentliche Netze”. Nürnberg: Philips Kommunikationssysteme, 1989.
• Gardiner, Andrew: DSM Desotech, “UV-cure fibre optic buffering resin”.
• Degussa, Germany: “High-Speed LSOH Buffering Materials”.