Case Study: Implementation of National Railway Dedicated Communication Optical Cable Project

Process 1: Cable Laying

1.Pre-Shift Roll Call

Before construction, all personnel gather at the worksite entrance for attendance and check tools. The construction supervisor gives a safety briefing, clarifying the scope, duration, and safety requirements of the work.

2.Cable Uncoiling

The standard cable reel length is 3 km. Before laying, cables should be uncoiled and arranged in a double “∞” pattern, facilitating simultaneous laying towards both ends (Cable A towards lower kilometer, Cable B towards higher kilometer) to improve efficiency. During uncoiling, avoid backlashes, stepping, or applying heavy pressure on the cable.

3.Cable Laying

Under bridges, cables are pulled via pulleys into high-speed rail troughs and laid using a cable puller. In straight sections, pulleys are installed every 20 m; in curves and key areas such as signal junction boxes, cover plates are opened to assist with pulleys. After laying, cables should lie naturally straight, with a bending radius no less than 25 times the outer diameter, clearly marked, without crossing existing cables, and with sufficient slack for maintenance.

4.Completion of Laying

After laying, remove auxiliary equipment from troughs and restore cover plates. Construction personnel withdraw in an orderly manner. Clean-up personnel push from both sides towards the passage to check for any leftover items.

Process 2: Cable Splicing

1.Preparation

Prepare the following tools before splicing: fusion splicer, cleaver, ring cutter, longitudinal slitter, stripping tools, splice closure, screwdrivers, pliers (various types), and tape. Clean the cable before starting the stripping process.

2.Cable Stripping

Use a ring cutter to cut the cable sheath: clamp the cable, tighten the handle, and rotate clockwise, following a principle of two rotations tighten once. Then use a longitudinal slitter to remove the outer jacket, and finally strip the inner jacket with a stripping knife (minimum length 2.7 m).

3.Cable Fixing

Install the cable on connection brackets with retaining rings, arranging the buffer tubes sequentially. The exposed part at the fixing point should be about 3 mm. Reinforced fibers are fixed to the side of the bracket, bent downward.

4.Fiber Storage in Closure

Ensure at least two loops of fiber slack inside the closure, with a length no less than 1.6 m. Mark buffer tubes, strip 2 cm near entry into storage, clean grease, sleeve each fiber individually with heat-shrink tube, and remove 2–3 cm coating at the fiber end.

5.Fusion Splicer Discharge Test

Set splicer parameters and perform discharge tests on prepared temporary fibers. Repeat as needed. Only proceed if results meet standards.

6.Fiber Splicing

Splice fibers according to loose tube and color sequence. Clean fibers with alcohol swabs, cleave ends to be smooth, clean, and angled less than 0.5°. Splice both ends, free of dust or bubbles, then apply heat shrink tubing. Keep the splicer wind cover closed, and center the heat shrink during preparation.

7.Fiber Storage

Arrange heat-shrink tubes sequentially. Store fibers from A and B cable sides simultaneously, preferably with an even number of loops to counteract torque. Maintain a bending radius no less than 40 mm.

8.Closure Sealing

Place the prepared storage tray into the splice closure. Install sealing gaskets properly, secure plugs, and tighten bolts diagonally in two steps.

Process 3: Splice Testing

1.Test Preparation

Confirm cable type, core count, test location, and time. Prepare necessary test instruments. Cables should have one end terminated or reliably looped for testing. For this project, a 288-core G.654E fiber is used; the average splice loss per fiber must not exceed 0.025 dB.

2.Splice Testing

Use “end-to-end fiber loop with moving detection points and bidirectional monitoring.” Set OTDR parameters (refractive index, pulse width, measurement range) and test each splice in both directions (A-B and B-A). If results fail, notify splicing personnel to redo. Record results and inform the next splice point.

3.Test Completion

Place a completed splice record card inside the closure, noting splice time, location, and personnel. Seal the closure, fix it on anti-vibration brackets in the trough, and perform verification testing. Save data and fill in the “Cable Splice Loss Test Record,” signed by onsite supervision.

Summary

National backbone communication projects are key initiatives supporting state strategy. Railway dedicated communication cable projects provide backup lines for the railway communication backbone. Implementation of this project supports the development of the digital economy and promotes regional coordination and national modernization.