Fiber-optic cable

“ The capstan was manned, and the cable hove up to a short stay. The topsails and top-gallant sails were set; then the anchor was hauled up to the hawse-hole, catted and fished. The Young America moved; she wore round, and her long voyage was commenced. The courses and the royals were set, and she moved majestically down the bay. The steamer kept close by her, and salutations by shouts, cheers, and the waving of handkerchiefs, were continually interchanged, till the ship was several miles outside of the lower light. ”

“ If the vessel rides at anchor with a short cable, her motion, as she rises and falls with the sea, raises up the shaft of the anchor, which has a tendency to detach the flukes, or points from the bottom. But Paul had been careful the night before to give the Fawn all the cable he could spare; and it was evident, therefore, that the anchor was not heavy enough, or that there was no holding-ground at the bottom.
"There is only one thing we can do, John," said Paul, desperately, after he had fully examined the situation of the boat. ”

“ I did not see him hold any communication with the captain, though he paused for a moment at the gangway, and looked over the rail into the boat."
"Might not the captain have handed him the package then?"
"I don't think it was possible, your honor."
"What were the men on the forecastle doing?"
"They were coiling away a spare cable—all but Bob Thomas, who was to pull the captain ashore; and the visitors were assisting them."
"That will do, Mr. Ebénier; we are much obliged to you for the lucid manner in which you have given your testimony, which is very important," said Squire Saunders. ”

“ The moon shone brightly on the deserted deck of the Josephine after the runaways had departed in the four boats,—deserted by all save Bitts, who was endeavoring to free himself from the rope by which he had been secured. Before the conspirators had gone a cable's length, he succeeded. Reaching the rope over his head, he went up, hand over hand, till he had slack enough to make a bight for one of his feet. Then, holding on with one hand, he loosed the rope from his neck with the other, and descended to the deck.
Rogues always overreach themselves. ”

“ All sail except the jib was set, and at the signal each craft was to slip her cable, hoist her jib, if she had one, and get under way, as quickly as possible. The "rode" was simply to be cast off, for the end of it was made fast to the tender, which was used as a buoy for the anchor.
"Are they all ready?" asked Donald, as the time drew near.
"All but the Juno. Laud has picked up two live weights, and wants another man," replied Sam Rodman. ”

“ Who has not seen men in the streets dragging huge pipes of lead through the open manholes from big wooden spools? These are the cables you talk over. They have been papered and clothed—and tarred and feathered, maybe—and then encased in lead by a process that is so easy as to be laughable, and yet as ingenious as any one thing the wire miller does. Unrolling slowly from its spool, the heavy cable moves up to a machine built strong and four-legged from the floor. ”

“ The order was repeated by the other officers till it came to the forecastle. Every seaman knew precisely what he was to do in the operation of weighing the anchor; and in a moment the bars were shipped and swiftered. All hands were then in position, and waiting for the next order.
“Heave around! Heave in the cable to a short stay!” added the first lieutenant; and the order went forward as before.
The first master had been directed to inform him when the cable had the proper scope, which had been indicated to him.
“Avast heaving!” said Tom Speers. ”

“ There was wind enough to take him down as far as the ledges, and then it suddenly subsided. Leopold furled his mainsail, for the calm indicated a coming squall. It [Pg 168] wanted an hour of high tide, and he anchored the Rosabel at a considerable distance from the shore, paying out the cable till the stern of the boat was in water not more than three feet deep. Pulling upon the rope till he was satisfied that the anchor had hooked upon one of the sharp rocks below the beach, he prepared to go on shore. ”

“ In the most general practice each wire is insulated from all others by a wrapping of paper ribbon, which covering is only adequate when very dry. Cables formed of paper-insulated wires, therefore, are covered by a seamless, continuous lead sheath, no part of the paper insulation of the wires being exposed to the atmosphere during the cable's entire life in service. Telephone cables for certain uses are formed of wires insulated with such materials as soft rubber, gutta-percha, and cotton or jute saturated with mineral compounds. ”

“ The attempt to insulate more than one conducting-wire or medium would not only have increased the chances of failure of all of them, but would have necessitated the adoption of a proportionably heavier and more cumbrous cable. The tensile power of the outer or wire covering of the cable, being very much less than that of the conductor within it, the latter is protected from any such strain as can possibly rupture it or endanger its insulation without an entire fracture of the cable. ”

“ In the case of the ungrounded sheath, the latter charges at once through all its length to the voltage of the high-potential wire; at some point, a wire within the cable is close enough to the sheath for an arc to strike across, and the trouble begins. All the wires in the cable are endangered if the cross be with a wire of the primary circuit of a high-tension transmission line. Any series arc-light circuit is a high-potential menace. Even a 450-volt trolley wire or feeder can burn a lead-covered cable entirely in two in a few seconds. ”

“ Whitehouse and Bright, electricians to his company, were instructed to begin a preliminary series of experiments. They united a continuous stretch of wires laid beneath land and water for a distance of 2,000 miles, and found that through this extraordinary circuit they could transmit as many as four signals per second. They inferred that an Atlantic cable would offer but little more resistance, and would therefore be electrically workable and commercially lucrative. ”

“ The hard-drawn copper wire of high conductivity (invented by T. B. Doolittle in 1877) is invariably used; and wires weighing from 150 to 800 lb. per mile have been employed. It was necessary to carry the long-distance lines through underground cables in the approaches to large English cities, but owing to the inefficiency of cable wires as compared with aerial wires for speech transmission, the length of underground cable sections was kept down to a minimum. ”

“ It consists of an exchange of currents sent alternately every ten minutes by each ship. These not only serve to give an accurate test of the continuity and insulation of the conducting-wire from end to end, but also to give certain signals which it is desirable to send for information purposes. For instance, every ten miles{121} of cable paid out is signalized from ship to ship, as also the approach to land or momentary stoppage for splicing, shifting to a fresh coil, etc. The current in its passage is made to pass through an electromagnetometer, [34] an instrument invented by Mr. Whitehouse. ”

“ The Board of Trade in 1859 had appointed a committee of experts, including Professor Wheatstone, to investigate the whole subject, and the results were published in a Blue-book. Profiting by these aids, an improved type of cable was designed. The core consisted of a strand of seven very pure copper wires weighing 300 lbs. a knot, coated with Chatterton's compound, which is impervious to water, then covered with four layers of gutta-percha alternating with four thin layers of the compound cementing the whole, and bringing the weight of the insulator to 400 lbs. ”

“ The future of telephone working, especially in large cities, is one of underground wires, and the way to get over the difficulties of this kind of work is perfectly clear. We must have metallic circuits, twisted wires, low resistance, and low capacity. In Paris a remarkable cable, made by Fortin-Herman, gives an exceedingly low capacity—viz., only 0.069 φ per mile. In the United States they are using a wire insulated with paper which gives 0.08 φ per mile. We are using in London Fowler-Waring cable giving a capacity of 1.8 φ per mile, the capacity of gutta-covered wire being 3 φ per mile. ”

“ The special properties of every knot or mile of the core are chronicled, so that a complete account of every part of the cable is preserved during its progress of manufacture. And after it is made, it is tested electrically every day, to see that no change takes place in its electric qualities. These electric tests are three in number: For resistance—the resistance of the copper wire to the passage of the current. For inductive capacity—the amount of charge or quantity of electricity which the cable will take up. For insulation resistance—the insulating power of the gutta-percha coating. ”

“ The natural increase in the number of aerial wires created a demand for better insulation and grouping in cables. Hundreds of miles of No. 12 iron wire were braided and dipped in suitable compound for this use. The annoyance from induction soon made a call for anti-induction cable. This want was supplied by a tin-foil cable so called, in which each conductor, after being insulated, was enclosed in a strip of this tin-foil. Cotton-covered wires to the extent of 50 or 100 were cabled together, and after being saturated with paraffine were placed in a lead pipe. ”

“ Altogether, in the four cables there would be 23,132 miles of wire, or enough to go nine tenths of the way around the earth.
The wire in a strand, he said, was looped around “shoes” at each end of the bridge, and ran in a continuous length, like a skein of silk. When the strand was completed, the ends were spliced together. When the strand was started, the wire was temporarily fastened at one end and passed around the shoe. Then it was slipped over the carrier, a signal was given, the cable started, and the carrier proceeded merrily on its way across the river. ”

“ Therefore the advantages in point of price of iron wire over copper in the first place, would be greatly overbalanced by the increased cost of insulating and sheathing it. It is of the greatest importance that the copper wire of the cable should be as pure as possible, for the slightest trace of arsenic or other foreign element is sufficient to hamper, in some mysterious way, the swift course of the subtle current, and very materially to weaken the conducting power of the wire. ”

“ A triple coating of gutta percha, to keep the sea from sucking out the electricity, and a thick coating of iron wire, to sink the cable to the bottom and give it strength, were added to the copper rope, and then the cable was complete. No less than 325,000 miles of iron and copper wire were woven into this great cable,—as much as might be wound thirteen times round the globe ”

“ He described 'high tension cables for 3,000 volts' having paper insulation impregnated 'with a rather thin liquid, oily and not too resinous mass' with cable joints bound with linen tape first boiled in oil so that it is completely saturated, with the wrapped joint inclosed in a lead sleeve, soldered to the lead sheath of the cable. Through a hole cut in the top of the sleeve or socket 'hot insulating mass is poured into the socket. ”

“ In the main the causes which hinder a pulse committed to a cable are two: induction, and the electrostatic capacity of the wire, that is, the capacity of the wire to take up a charge of its own, just as if it were the metal of a Leyden jar.
Let us first consider induction. As a current takes its way through the copper core it induces in its surroundings a second and opposing current. For this the remedy is one too costly to be applied. Were a cable manufactured in a double line, as in the best telephonic circuits, induction, with its retarding and quenching effects, would be neutralized. ”

“ After passing through such elaborate tests, all will be glad to see the final product of so much care and skill. As the long line begins to reel off from the great wheels and drums, we may examine it in its completed and more perfect form. It is only necessary to compare it with the cable laid in 1858, to show its immense superiority. A glance at the two as they appear on the preceding page will show that the cable had grown since first it was planted in the ocean, as if it were a living product of the sea. This growth had been in every part, from core to circumference. ”

“ The signals are retarded (and this was one of the results of the investigation) in such a manner "that the time required to reach a stated fraction of the maximum strength of current at the remote end," when a given potential difference is applied at the other, or home end, is proportional to the product of the capacity and resistance of the cable, each taken per unit of the length, and also proportional to the square of the length of cable. ”

“ So they spent more money, laid more cables, failed again, toiled and moiled and worked like beavers for years, until at last in 1866 they finished a cable from Ireland to Nova Scotia that worked like a charm. It was, without exception, the greatest piece of work ever done in electricity, and its history is one of the finest of the many tales of engineering enterprise.
To-day there are about a dozen cables between North America and Europe, and three between South America and Europe. There are cables in every sea and ocean in the world, and across every ocean except the Pacific. ”