Chapter 9 — The Cable Splicer Beneath the Sea

Vascular Grafting in a Dry Chamber

The next evening, the sea waves were much higher than the previous day. The first waves continuously slapped the side of the Vạn Lý ship, causing the entire DP2 dynamic positioning system to work at almost full capacity to keep the ship fixed on the repair point. In the control room, Bằng watched the screen display the thrust of each directional propeller, the graph bars flashing continuously as the system automatically adjusted to compensate for each wave jostling the ship's hull.

"DP is having to make up thirty percent more than this morning." Reporting through the communication, his voice was more tense than usual. "It's still within the safe threshold, but if the waves continue to increase, I will have to reconsider keeping the ship stationary for a long time."

On the seabed, at the new splicing point three meters from the unstable cliff towards the flat sandy floor, Sơn and Bách are assembling a dome-shaped metal structure called a dry chamber, or habitat, a small chamber filled with air to create a water-free environment, allowing for fiber optic splicing that requires near-absolute precision.

"The dry chamber has stabilized, the pressure inside is equal to the outside." Sơn reported, after checking the watertight joints one last time. "Start dry pumping."

The water inside the dry chamber gradually recedes through the valve system, leaving a small space only enough for two people to work. The air inside is dry even though the outside is still under the terrible pressure of eighty-five meters of surrounding sea water. Sơn took off his diving helmet, revealing his face for the first time since going underwater, and took a breath of dry air thick with the smell of metal and insulating plastic.

"Starting the pairing process," he spoke, his voice over the communication had now returned to normal, no longer having the altered timbre of heliox gas when out of water.

Bách opened the specialized tool box, inside was a miniature fiber optic fusion welding machine, specially designed to operate in conditions of vibration and high humidity even in a dry environment. He placed the two ends of the twelve-meter replacement cable, which had just been pulled down from the ship via a separate pulley system, onto a small work table fixed to the wall of the dry chamber.

"Remove the protective cover, clean the fiber surface." Bách read aloud each step according to the checklist, a mandatory habit in the undersea docking process, where no one can go back to check if a step is missed. "Cut the end of the fiber flat with a specialized cutter, the cutting angle must be half a degree less than the perpendicular plane," Sơn observed through a magnifying glass mounted on the welding machine, where the image of the two ends of the optical fiber, thinner than a strand of hair, was magnified dozens of times. "Cutting angle meets standard. Align optical axis."

The welding machine automatically performs the alignment step, the two ends of the fiber move small distances that are imperceptible to the naked eye, until both optical axes are perfectly aligned according to the measurement of the optical sensor inside the machine.

"Arc discharge, heat welding." Bách pressed the button, a tiny spark flashed in the welding machine's cavity, gently melting the two ends of the fiber together into a seamless connection, with no gaps visible under the integrated microscope.

"0.03 decibel joint loss." Sơn reads the results displayed on the welding machine's small screen, a number that is almost perfect by industry standards. "Satisfactory, much lower than the allowable threshold of 0.1 decibels. There is one more connection."

On the ship, Thư monitored the entire process via a camera mounted in the dry chamber, recorded each parameter into the system, and compared it with the standard table she had memorized before the trip. "Confirmed from the water, the first connection meets standards." She reported, unable to hide the slight excitement in her voice as she witnessed live a fiber optic splice being made on the deep sea floor for the first time.

"Don't be too happy yet, there's still half way to go," Sơn reminded, not to let himself or Bách feel down even though the first connection was successful. "The process is the same for the second joint, don't be subjective just because the first time went well."

Bách began to repeat the entire sequence with the other end of the cable, slowly and meticulously no less than before, even though beads of sweat had begun to form on his forehead as the dry chamber space became increasingly hotter from the heat from the continuously operating electronic equipment. He had just finished separating the protective cover and preparing to clean the fiber optic surface, when a strong vibration suddenly passed through the entire dry chamber structure, causing the operating table to wobble slightly, and the specialized cutting knife almost slipped out of his hand.

"What's up?" Sơn asked immediately through the internal communication between the two people in the dry room, and at the same time called to board the ship.

"A wave much larger than the previous ones just hit the side of the ship, DP had to suddenly compensate with the greatest force from the beginning of the shift until now," Bằng answered immediately, his voice urgent, clearly busy with the series of warnings appearing on his screen. "Checking to see if there is any impact on the dry chamber suspension system."

"Recheck stability before continuing." Sơn ordered, his eyes quickly scanning the joints and pressure indicators displayed on the small control panel mounted in the compartment. "Bách, stop, wait for confirmation."

A few tense seconds passed. On the control panel in the dry chamber, a yellow warning light came on, signaling that the pressure at a joint above the chamber was fluctuating slightly beyond normal levels, although not yet reaching a dangerous threshold.

"There are slight pressure fluctuations at the upper joint." Sơn reported to the train, his voice still remaining calm but had switched to high alert mode. "It hasn't reached the dangerous threshold, but I don't want to continue the sensitive welding process while DP is still having to compensate so strongly."

"Agree," Hòa spoke from the cockpit, his voice decisive. "Pause the second docking stage. Return the two of you to the diving bell, wait for the waves to stabilize, then continue."

"There's only one connection left, almost done," Bách spoke through the comm, his voice was a bit regretful, not against the order, just the instinct of a person who doesn't want to leave what he's doing unfinished.

Sơn heard that sentence, and for a moment, it echoed in his head almost exactly like another sentence, from another voice, three years ago: there's one last joint, almost finished. He tightened his grip around the tool he was holding, forcing himself back to the present.

"Are not," Sơn said, his voice more decisive than Hòa's just now. "Almost done doesn't mean it's done. Temporarily pack the unfinished cable end, make sure no water gets in, then pull it out as ordered by the captain."

Bách looked at Sơn, realizing that there was something in his voice that was more serious than a normal technical decision, but this was not the time to ask more questions. He nodded and began the process of temporarily packing the unfinished cable end according to the instructions.

Fifteen minutes later, the dry chamber was pumped back with water, the two people put their diving helmets back on, and swam back to the diving bell in the water that had become much more chaotic than when they got down. On the ship, everyone watched via camera, witnessing the first connection being successfully completed, but the second connection was still unfinished, temporarily wrapped in a protective shell waiting, like an unfinished sentence, hanging in the middle of the sea.

"One connection done, one connection left, and the storm is still getting closer by the hour." Hòa summed up, looking out the cockpit window where the afternoon sky was unusually dark compared to the actual time, as if night was coming earlier to make room for something else.

When the diving bell was pulled up close to the ship's hull, Thư stood at the communication control panel, her eyes never leaving the screen displaying Sơn and Bách's breathing rates. The two parallel sound waves were still steady despite going through a more stressful work shift than expected. She remembered what Sơn had said through contact earlier — nearly done is not done — and wrote it down in her notebook, not as a technical term, but as a principle she wanted to carry with her throughout her career.

By turning off some unnecessary warnings on the screen, rubbing your temples that are tense after many hours of intense concentration. "Give me ten minutes to rest before planning the dive to complete the last connection," he said, his voice tired but unfazed. "Then we need to get the whole team together and see how much of the remaining weather window really is." Hòa nodded, agreeing, his eyes still glued to the darkening sky outside, where the boundary between natural sunset and the darkness of an approaching storm cloud system had become more difficult to distinguish than ever. Those ten minutes of short rest, he knew, would pass quickly, faster than anyone on the ship wanted.