Optical fibre unit for air-blown installation
It is disclosed an optical fibre unit for air-blown installations comprising: a first group of optical fibres embedded in a resin layer; a sheath arranged in a radially outer position with respect to the resin layer so that an annular space is formed between resin layer and sheath; and a second group of optical fibres arranged in the annular space. Also disclosed are an apparatus and a method for manufacturing such optical fibre unit.
1 . An optical fibre unit for air-blown installation comprising:
a first group of optical fibres;
a resin layer substantially completely embedding the first group of optical fibres;
a sheath arranged in a radially outer position with respect to the resin layer so that an annular space is formed between resin layer and sheath;
a water blocking material in the annular space; and
a second group of optical fibres arranged in the annular space, the optical fibres of the second group of optical fibres being laid about the resin layer and each substantial parallel to a longitudinal axis of the optical fibre unit, the second group of optical fibres each being completely embedded in the water blocking material.
2 . The optical fibre unit according to claim 1 , wherein the second group of optical fibres is arranged about the resin layer in at least one layer substantially coaxial with the resin layer.
3 . The optical fibre unit according to claim 1 , wherein the annular space formed between the resin layer and the sheath is filled with a water blocking material, the second group of optical fibres being embedded in the water blocking material.
4 . The optical fibre unit according to claim 1 , wherein the first group of optical fibres comprises at most 12 optical fibres.
5 . The optical fibre unit according to claim 1 , wherein the resin layer has a diameter between 0.9 mm and 1.5 mm.
6 . The optical fibre unit according to claim 1 , wherein the resin layer comprises at least one acrylate material.
7 . The optical fibre unit according to claim 1 , wherein the resin layer comprises a first layer of resin material and a second layer of resin material radially outer to the first layer of resin material, wherein the second layer of resin material has a secant modulus higher than a secant modulus of the first layer of resin material.
8 . The optical fibre unit according to claim 7 , wherein the secant modulus of the first layer is between 0.5 MPa and 25 MPa.
9 . The optical fibre unit according to claim 7 , wherein the secant modulus of the second layer is between 500 MPa and 1000 MPa.
10 . The optical fibre unit according to claim 1 , wherein the sheath comprises a polyethylene as base polymer.
11 . The optical fibre unit according to claim 1 , wherein the sheath has a radial thickness between 100 μm and 250 μm.
12 . The optical fibre unit according to claim 1 , wherein the water blocking material is gel.
13 . The optical fibre unit according to claim 1 , wherein the water blocking material is grease.
14 . A method for manufacturing an optical fibre unit for air-blown installation, the method comprising:
providing a first group of optical fibres;
substantially completely embedding the first group of optical fibres in a resin layer;
arranging a second group of optical fibres about the resin layer, the optical fibres of the second group of optical fibres being laid about the resin layer and each substantial parallel to a longitudinal axis of the optical fibre unit;
providing a sheath in a radially outer position with respect to the resin layer so that an annular space is formed between the resin layer and the sheath, the second group of optical fibres being arranged in the annular space; and
providing a water blocking material in the annular space, the second group of optical fibres each being completely embedded in the water blocking material.
15 . The method of claim 14 , comprising providing a water blocking material about the resin layer.
16 . The method of claim 15 , wherein the providing the water blocking material is carried out before the arranging the second group of optical fibres.
17 . The method of claim 15 , wherein the providing the water blocking material is carried out after the arranging the second group of optical fibres.
18 . An optical fibre unit for air-blown installation comprising:
a first group of optical fibres;
a resin layer substantially completely embedding the first group of optical fibres;
a sheath arranged in a radially outer position with respect to the resin layer so that an annular space is formed between resin layer and sheath, wherein the sheath is substantially coaxial with the resin layer and the annular space has a substantially constant thickness; and
a second group of optical fibres arranged in the annular space, the optical fibres of the second group of optical fibres being laid about the resin layer, the second group of optical fibres each being completely embedded in a water blocking material within the annual space.