Optical Fiber Communication for Indian Railways

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Optical Fibre Communication System

• Optical Fibre Communication System serves as the backbone for all types of communication needs for Indian Railways.
• Examples are control communication, administrative data, mobile train radio, IP networks, and modern signaling.

Guidelines for Optical Fibre System Use

• Configuration should utilize 24/48 Fibres Optical Fibre Cable as per latest RDSO specification plus 6 Quad Jelly Filled Quad cable as per RDSO specification.
• All Optical Fibre Cable shall be laid in HDPE pipe using blowing method.
• One pair of fibers for comms.
• Second fiber pair kept in reserve.
• Remaining fibers transferred to Railtel for revenue; some can be reclaimed if necessary.
• IP-MPLS network to be installed for short and long haul communication, with redundant equipment/routes.
• Short Haul Communication is currently on STM-1 System with Primary Digital Multiplexers (PDMUX).
• VOIP to be used for Control Communication on STM but shifting to IP MPLS.
• Long haul communication to utilize Railtel's network.

System Design Considerations

• Important factors for system design are station/nodes location, optical loss budget, and system capacity to meet current & future needs.
• Availability/Reliability, power supply, plus estimate preparations.

Locating Optic Fibre Equipment Rooms

• System planning details locations for fibre optic equipment along the route.
• Exact location determined via surveying, keeping section 13.2.2 considerations in mind.

Survey of Existing Buildings

• Scan building at station for optic fibre equipment room, to optimize existing infrastructure and cost.
• Utilisation should depend on expenditure for room modifications being less than construction costs.
• Must have sufficient total area per Section-III and be near cable route.
• Power (preferably standby) must be available and the site above highest flood level.
• Should avoid track crossings and preferably be close to/in the station building.

New OFC Building Considerations

• Should be near the station building.
• Not near Restaurants/tea stalls and must be on level ground.
• Avoid areas between tracks, preferably on same side as optic fibre cable route
• Site should possess road access plus sufficient open space for equipment storage.
• Site should have construction of tower for train radio and minimum distance of copper cable to OFC room.
• For security, location should be close to the ASM's Office.

Control Room Location

• OFC room must be within the control office complex.

Building Layout

• Wayside OFC rooms: Drawing No. RDSO/TCDO/COP-1(a).
• Main control station/Critical Nodes: Drawing No. RDSO/TCDO/ COP-2(a).

Building Requirements

• Construction of bricks and concrete wth sturdy front door to prevent intruders
• Sealing that prevents dust
• Cable pit near OFC room should have depth of 1.25 m plus two 100 mm dia RCC pipes for separate OFC/quad cables.
• Pipes extend 2m away from cable pit, one end opening at pit bottom.
• End of RCC pipes sealed with Plaster of Paris.
• AT Power supply/standby with remote monitoring should be provided.
• Use concealed wiring for electrical fittings.
• Oil distemper for lasting 10-12 years to avoid frequent distempering.
• Floor cover with PVC or other suitable synthetic tiles.
• Battery room: rain-protected exhaust fan with wire mesh, acid-proof tiles.
• Air Conditioning in critical OFC backbone locations with high ambient temperature.
• Ventilation arrangements as per Drawing No. RDSO/TCDO/COP-1(a) & 2(a).
• Wire mesh on windows/ventilators to prevent theft and rodents.
• Earthing arrangements near the OFC room.

Equipment Layout

• Layout should be as per Drawing Nos. RDSO/TCDO/COP-03(a) and RDSO/TCDO/COP-04(a) at wayside stations and control office.
• Equipment must fit standard 19” racks.
• The wiring from battery to the location of equipment will be inside PVC channels of suitable size.

Preliminary Survey of Optic Fibre Cable Route: Main Items

• Selection of the route and number of drop/insert locations.
• Size and cable length assessment for the cable.
• Work out the circuit requirements and heavy tool/plant needs.
• Assess special sectional concerns like soil, cuttings, embankments, waterlogged areas, bridges, and yards.
• Collect details of existing telecommunication and electrification requirements, then prepare tapping diagrams.
• Assess track crossings and other protective works.
• Avoid newly laid track, embankment toe, burrow pits, waterlogging, cinders, fertilized soils, and proximity to chemical industries.
• Avoid large rock cuttings, jungles, routes of existing cables, or difficult areas.
• Carefully select the cable hut approaches and the cable protection.
• Work out circuit requirements, cable chart, and tapping diagrams.
• Determine transportation requirements.
• Avoid the side of alignment that has earthwork/supply structure alteration risk.

Cable Route Plan and Tapping Diagrams

• Indicate route relative to main line center of track
• Whether the route along the DN main line or UP main line in case of double line sections
• Indicate sides of the main line
• Prepare a tentative tappings diagram for the section
• Indicate route proximity to permanent structures for identification.

Cable Route Selection Considerations

• Distinct advantage to account for terrain conditions which vary greatly.
• Frequent track crossings are undesirable.
• Avoid underground structures, signaling, and power cables, plus pipelines.
• Avoid built-up drainage areas.
• Select opposite side of existing Railway signal cables.
• Route through small culvert beds via HDD method.
• Avoid termite/rodent areas.
• Preference is to favor the main line away from coastal side.

Purpose and Procedure for Detailed Cable Route Survey

• Purpose; closer study of telecomm. facilities. + identify material needs.
• Finalize all drawings/site plans required.
• Collect data preliminary to propose revisions.
• Prepare 5 kilometer charts for main cable route with 10 cm = 1 km scale.
• Document ASM offices, cabins, and OHE posts on charts and label the 'LOC' column.
• At every 10cm mark km post number.
• Enter the equivalent chainage per OHE survey plan (required for cable length calculations).
• Document the station name against its point on the Station Master's office.
• As well serial number and length of culverts, bridges.
• Line shall be marked on the ‘Track Line’ of the cable route plan.

Finalizing the Route: Guidelines

• Use latest OHE
• Collect Survey plan for 5 km charts.
• Important locations by 30m steel tape.
• Locations termed special terrains due to obstruction
• Portions falling in category stated in para.
• Actual chain along the route.
• Control office along route.
• Cable, drum lengths along main line up to OHE Plan.
• Separation distance from track's center in special terrains.
• A minimum of 5.75 m distance maintained between OHE masts and cable limited to 1m ensuring OFC is laid in HDPE
• Push trolley along the track.
• For the cable passing over the culverts.
• Near OHE, switching posts shall be walk on the surface.

Cable Length Estimation

• Cable entry to cabin to follow Number RDSO/TCDO/COP-18.
• Cable length to be worked out from route length per measurement with 2.5% allowance.
• Extra for track crossing, including 2.5m loop on each side.
• 10m extra for bridge and culvert approach with measurement.
• 5m cable kept on either side of steel bridges and 2.5m on short bridges.
• A 10 meter loop on either side must be kept at every joint.
• A 10 meter loop must be kept in the cable pit.

Tools and Equipments

• General: practices include damage or deterioration of cable handling.
• Cable kept with strong surface and use sleepers.
• Drums may not be stacked, stoppers for stability.
• Drums will remain accessible for lifting and remain remote.
• Drums drum rotated in direction of arrow during unloading.
• Drums not be rolled over objects.
• Transit drums inspected for damage and layers.
• Drums upright, ends tied, all battens left until unrolling.

Cable Drum Loading/Unloading

• Drums lifted to avoid damages and direct impact.
• Drum with fork lift truck.
• The cable spindle with central hole.
• The Cable and HDPE pipe in closed using their end cap.

Work Flow Diagram

• Cable laying: Armored fibre cable, Duct is conforming to TEC/RDSO.
• The materials and tools has detailed section. before that the tools metal, warehouse, public, fire plug,
• Cable: Inspect specifications for materials and work.

Traffic and Safety, plus Duct Burying Depth:

• Telecom cable laid as a traffic safety and boundary should be more wide where the traffic is more regular.
• The cable route must have “work in progress” and signs, in order.
• The depth the cable shall use the standards and artificial damages.

The Standard and Excavation :

• The standard trench: laying and four types.
• Cable Laying: Before cable , ensure no obstacles on the route.
• Cable-laying, manual: Pipes, or uneven surfaces.
• Machine: Excavation is done mechanically, bucket, cleaning and pulling.

Handling, Laying, duct level, Duct

• Unload carefully, and protect them till the end,
• The coil un rolled at a place, it be moved where workers can take it, never dragged.
• All care should be taken with the coil when it is broken by them.
• Same workers must be use there.

Laying and Duct Preparation, Plus Cable Preparation :

• Inspection must show specification, clean, smooth and rocks less
• Cable lifted to trench for aid.
• Shouting, steady, and even.
• A number of man needed for the line or job with wire.
• One man must inspect damage, flex used to protect damage in trench.
• The joint and tools in section need to be checked
• Vhf, cable, manhole, man used to test is its works.
• Then is use with the other tests and has the OTDR

Cable Installation and Trenches :

1. Which of the following is a characteristic of the Optical Fibre Communication System according to the text? a) It is only for railway emergency communications. b) It is the backbone for all types of communication needs for Indian Railways. c) It is exclusively for administrative voice communication. d) It is limited to modern signaling applications.

2. What is the recommended fiber configuration to be used for Optical Fibre systems? a) 12 Fibres Optical Fibre Cable as per RDSO specification b) 24/48 Fibres Optical Fibre Cable as per latest RDSO specification with a specific quad cable. c) 6 Quad Jelly Filled Quad cable only, following any available specification. d) Any available Optical Fibre Cable will suffice the purpose.

3. What is the current system used for Short Haul Communication? a) IP-MPLS network. b) STM-1 System with Primary Digital Multiplexers (PDMUX). c) Railtel’s network. d) VOIP system.

4. In system design, which of these is NOT mentioned as a factor to consider? a) Location of optic fibre stations/nodes. b) Colour of the optic fibre cables. c) Requirement of system capacity to meet present and future needs. d) Optical loss budget between adjacent nodes.

5. What is the minimum depth at any track crossing with RCC/DWC duct?

   a) 0.8 meters b) 1 meter c) 1.2 meters d) 1.5 meters