EuroWire March 2022

Technical Article

Development of 576F optical cable with 200μm fibre rollable ribbon for microduct blown installation By Kohei Matsuura and Tetsuya Yasutomi, Optical Fiber Cable Production Dept, Furukawa Electric Co, Ltd, Japan

Abstract With the spread of Internet services, data transmission through optical networks is increasing. To achieve an efficient optical network construction, we have developed a 576F high-density optical fibre cable that can be installed in a microduct by the air- blown method. Using the 12F rollable ribbon made of optical fibres of 200µm diameter, both smaller diameter/higher density of the cable and good fusion splicing workability were achieved. Since the developed cable showed good results in the evaluation of transmission loss characteristics, temperature characteristics, mechanical characteristics and the blown installation test, it was confirmed to be up to the practical level. 1 Introduction With the spread of Internet services, the volume of data trans- mission through optical networks is increasing and hence, increase in speed and capacity of optical communication is demanded constantly. Optical cables laid underground are generally installed in ducts. Among them, the small-diameter optical cables, called microcables, can be efficiently installed in microducts by the air-blown method that uses the flow of compressed air, and this method is widely used throughout the world as one of the optical cable laying methods. In order to efficiently expand the optical network, it is preferable to lay a cable with a large number of optical fibres mounted in the existing microduct. However, the outer diameter of the cable that can be laid is limited by the inner diameter of the microduct. Moreover, if the number of fibres increases, there is a concern that the splicing work of the optical fibres will take a long time. For microcables laid by the air-blown method, many researchers have reported cables of various structures [1] [2] . Until now, we have been developing high-density optical cables that use rollable ribbons [3] . By using rollable ribbons, the cables can be made smaller in diameter and higher in density, and the shortening of the splicing time of the optical fibre during installation becomes possible. Further, we have reported that by using a small-diameter optical fibre of 200µm diameter, it is possible to realise a further ultra-high fibre count and high- density optical cable [4] . Here, applying the rollable ribbon technology that uses small- diameter optical fibres of 200µm diameter and the cabling technology to mount them at high density, to microcables, we have developed a 576F small-diameter, high-density optical fibre cable that can be installed in existing microducts using the air- blown method.

2 Cable design 2.1 Rollable ribbon

Figure 1 shows the structure of the ribbon used here. This is called the rollable ribbon and it has a structure where the 12 coloured fibres are intermittently bonded in a mesh shape. The rollable ribbon can be deformed and rolled when assembled in a cable. Thus, while being a cable made of ribbon, since high- density packing equivalent to a single fibre cable is possible, a small-diameter, lightweight cable can be realised. Further, to restore the ribbon shape when taken out of the cable, mass fusion splicing can be made with a fusion splicer, similar to a conventional optical fibre ribbon. Hence, the splicing work time, which is a concern in multicore cables, can be significantly reduced. By printing the barcode on the surface of the rollable ribbon, it is possible to identify the ribbon number ( Figure 2 ). Here, in order to reduce the diameter and weight of the cable, we have applied a small-diameter optical fibre of 200µm diameter to the rollable ribbon. The splicing of 12F rollable ribbons made of optical fibres of 200µm diameter can be achieved by using a conventional fusion splicer with a dedicated tool. Thus, a splicing similar to conventional ribbons or rollable ribbons consisting of optical fibres of 250µm diameter is possible [4] .

200µm fibre

Bonding part

Figure 1 : Rollable ribbon

200µm fibre rollable ribbon

Block=5 Bar=1

Figure 2 : Printed barcodes on the rollable ribbon of No 12

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March 2022