| 摘要 |
<p>Multiple optical fibre cables consisting of fibres equally spaced in a polyethylene ribbon (19) are produced in lengths of about a km and laid underground with manholes, to make spliced joints or repairs as the need arises. Connection losses can be high but this technique uses end to end cable termination with a resultant loss of less than 0.5 dB. A strap (17) is placed over the cable and a length of fibre exposed from the strap to the end of the cable (18). This is introduced into the block at an angle between 30 and 40 degrees to the base and clamped against a stop. The fibres are guided between curved cylindrical rails (8), which have the same diameter as the cable spacing, up to a stop (13) in the centre of the block, clamped, glued and the stop removed. Variation in the lengths of the fibres is accommodated by the flexibility of the fibres between centre and end of the block. The connecting cable is introduced in the same way from the opposite side. To the central well in which the fibres are butt joined is added an oil or polymer with a similar refractive index to the fibre core, to reduce losses.</p> |
