Punjab PSEB Matric NSQF Telecom (Optical Fiber Splicer) cheat sheet

Total internal reflection occurs when light travelling in the core strikes the core–cladding boundary above the critical angle; this requires core refractive index n1 greater than cladding index n2.

Numerical aperture: NA = sqrt(n1^2 − n2^2); the acceptance angle in air is θa = sin^-1(NA), so a higher NA accepts a wider cone of light.

Relative refractive index difference: Δ = (n1^2 − n2^2) / (2·n1^2), approximately (n1 − n2)/n1 for small differences.

V-number: V = (2πa/λ)·NA, where a is core radius; single-mode operation needs V below about 2.405.

Standard single-mode fiber at 1310 nm has zero material dispersion; at 1550 nm attenuation is lowest, near 0.2 dB/km, but chromatic dispersion is about 17 ps/(nm·km).

Attenuation in dB = 10·log10(Pin/Pout); loss per km = attenuation / length. Rayleigh scattering falls as 1/λ^4 and dominates below about 1600 nm.

Macrobending loss rises sharply below the specified minimum bend radius; microbending comes from coating or cable stress and shows as elevated loss at 1625 nm.

Modal dispersion limits multimode fiber bandwidth; graded-index profiles reduce it, and 850 nm VCSEL links dominate short-reach multimode use.

Single-mode fiber is identified by a 9 µm core in yellow jacket; multimode OM1/OM2 are orange (50/125 and 62.5/125), OM3/OM4 are aqua, and OM5 is lime green.

TIA-598 fiber colour sequence for a 12-fiber group: blue, orange, green, brown, slate, white, red, black, yellow, violet, rose, aqua.

Buffer tubes are counted with the same 12-colour sequence, and groups beyond 12 repeat colours with tracers or binder threads.

Loose-tube cable suits outdoor duct and aerial routes; tight-buffered cable suits indoor riser, plenum and patch-cord use.

Strength members (aramid yarn or FRP rods) carry tensile load; the jacket protects against moisture and abrasion, and the central member controls bend behaviour.

Armoured cable adds a corrugated steel tape for rodent and crush protection; double-jacket construction adds an inner sheath for direct-buried use.

OS2 single-mode cable is specified for 1310/1550 nm long-haul use, while OM3/OM4 are optimised for 850 nm laser sources in data centres.

Ripcord removal direction and jacket markings (fiber count, type, year, length marks) must be read before cutting, so the correct end and length are retained.

Fusion splicer kit: cleaver, stripping tool for 250 µm and 900 µm buffers, lint-free wipes, 99% isopropyl alcohol, splice protection sleeves, heat oven, and fibre scrap bin.

Cleaver blade life is finite; a worn blade gives angled or hacked end faces and elevated splice loss, so blade position and rotation must be tracked.

An optical power meter and a calibrated light source together measure link loss; an OTDR measures distance-resolved loss and reflections.

A visual fault locator (red laser) locates breaks, tight bends and bad connectors within a few kilometres; it is not an eye-safe substitute for a live-fibre check.

A fibre inspection scope with 200x or 400x magnification is used to check connector end faces before mating; a single dust particle causes high loss and permanent damage.

Never look into a live fibre or connector; use an optical power meter to confirm no light is present before splicing or cleaning.

Mandrel wraps of 5 turns around a 25 mm or 30 mm mandrel on 1310/1550 nm fibre allow a live-fibre check with a power meter without disconnecting.

Working tools must be insulated and rated for the voltage class in use; splicing in a manhole requires gas testing before entry and continuous forced ventilation.

Cable preparation sequence: measure and mark the sheath length, ring-cut the jacket, remove sheath, cut aramid and central member to the closure's specified lengths, then expose buffer tubes.

Buffer tube stripping exposes 250 µm fibres; the tube is scored and pulled, and the gel is cleaned with lint-free wipes and 99% IPA, never with a dry tissue alone.

Coating stripping removes the 250 µm acrylate to bare 125 µm glass over 30–40 mm; the tool must be matched to the coating diameter to avoid nicks.

A good cleave has an end-face angle of 0.5° or less and no hackle, lip or mist; the cleaver must be checked with the splicer's end-face viewer.

Cleave length must match the splicer's specified value (commonly 8–16 mm of bare fibre) so the fibre seats correctly in the V-grooves.

Cleaved fibre must never touch anything before splicing; even a light brush against the coating or the splicer body contaminates the end face.

Fibre scraps must go into a sealed scrap container, never onto the floor or into clothing, because bare glass splinters are difficult to see and remove.

Excess bare fibre beyond the arc region is trimmed only with the splicer's built-in cutter or a cleaver, never with side cutters.

Fusion splicing steps: strip, clean, cleave, load into the splicer, check end faces on screen, align, arc-fuse, estimate loss, apply heat-shrink splice protector, cool.

Arc check (arc calibration) is performed before a splicing session and after a change of electrode, altitude or humidity, because arc power drifts with electrode wear.

Typical good fusion splice loss for single-mode fibre is 0.05 dB or less; a splicer estimate above about 0.1 dB should be rejected and re-spliced.

Electrode life is typically several thousand arcs; worn electrodes cause weak arcs, bubbles and high loss, and must be replaced in matched pairs.

Mechanical splicing uses a precision alignment sleeve with index-matching gel; typical loss is 0.1–0.3 dB, and it is preferred where no power is available or for quick repairs.

Splice protectors are heat-shrink tubes with a stainless steel strength rod; they must be centred over the bare fibre and fully shrunk in the heat oven.

Splicing different fibre types (for example 250 µm to 900 µm) requires the correct holder and mode; mismatched mode field diameters add intrinsic loss.

After splicing, the splice tray must hold fibres at a bend radius of at least 30 mm and protectors must not be kinked or stacked under tension.

Insertion loss (dB) = 10·log10(Pin/Pout); a two-power-meter method compares reference power before and after inserting the splice or link.

Splice loss by the cut-back method: measure output power with a long length, cleave back near the source, measure again, and take the difference in dB.

OTDR measures backscatter versus distance; a splice appears as a step drop, and the loss is read between the backscatter levels on either side.

OTDR dead zones: the event dead zone is about 1 m and the attenuation dead zone about 4 m for typical settings; short patch cords cannot be resolved without a launch fibre.

Reflectance in dB is negative (for example −50 dB for a good APC splice); a reflective spike at a splice indicates an air gap or bad cleave.

Bidirectional OTDR averaging is required because splice loss readings differ with direction when fibres have different backscatter coefficients.

Power meter testing uses a reference (one-jumper or two-jumper) method; the reference must be set with the same connectors and wavelength as the link under test.

Test wavelengths: 1310 nm and 1550 nm for single-mode, 850 nm and 1300 nm for multimode; a link must pass at every specified wavelength, not just one.

Closure selection depends on environment: inline or dome closures for buried and aerial, and dedicated closures for duct and manhole; IP68 rating indicates dust-tight and water-immersion protection.

Cable sheath must be bonded and earthed through the closure's metallic strength-member clamp; the earth bond must be continuous across the joint.

Heat-shrink or cold-applied sealing must cover the sheath entry; an unsealed entry admits water, and water in a loose tube causes loss at low temperature as it freezes.

Splice trays are stacked and hinged; each tray holds typically 12 or 24 splices, and fibres must be routed with a minimum 30 mm bend radius.

Slack loops are stored in the closure or coil box so that re-entry and re-splicing is possible; excess fibre must not be crushed when the closure is closed.

Closure pressure testing or a visual seal check is done before backfill; buried closures are marked with a route marker and recorded with GPS coordinates.

Aerial closures must be mounted with the specified slack span and spiral hanger so that wind vibration does not fatigue the cable at the entry.

Documentation for each joint: closure ID, cable IDs, fibre numbers spliced, tray assignment, loss values, date, and technician name.

A PON is a point-to-multipoint tree: OLT in the exchange, ODN with fibre and passive splitters, and ONT/ONU at the subscriber premises.

GPON downstream is 2.488 Gbit/s and upstream 1.244 Gbit/s; XG-PON is 10G/2.5G and XGS-PON is symmetric 10G/10G.

GPON downstream uses 1490 nm and upstream 1310 nm; 1550 nm is reserved for RF video overlay, and 1625 nm is used for live-fibre testing.

Power budget: link loss = fibre attenuation + splice loss + connector loss + splitter loss; a 1:32 splitter contributes about 16.5 dB, a 1:8 splitter about 10.5 dB.

Splitter loss in dB ≈ 10·log10(N) plus excess loss; class B+ GPON budgets about 28 dB and class C+ about 32 dB.

Downstream data is broadcast and encrypted; upstream uses TDMA, and the OLT grants time slots so ONTs do not collide.

ONT ranging compensates for different fibre distances so that all ONT bursts arrive at the OLT aligned in the upstream frame.

FTTx topologies: FTTH (fibre to the home), FTTB (to the building), FTTC (to the cabinet) and FTTN (to the node); only FTTH is fully passive to the premises.

Laser safety: treat every fibre as live; never view an end face or connector with the naked eye or an ordinary magnifier, and use only an indirect scope with an IR filter.

Class 1M/3R sources at 1310/1550 nm are invisible and focus on the retina; a fibre break can emit enough power to cause permanent eye damage.

Chemical safety: isopropyl alcohol is flammable and a respiratory irritant; store it in a labelled closed container, away from arcs and heat, with ventilation.

Manhole and trench entry requires gas testing for oxygen, combustible gas, hydrogen sulphide and carbon monoxide, plus a standby person and harness.

Waste segregation: fibre scraps in rigid sealed containers, gel and solvent waste as hazardous waste, and lead-acid or lithium batteries returned to the supplier.

Electrical safety: use lock-out/tag-out on powered OLT and rectifier equipment, and verify absence of voltage before working in a joint or cabinet.

Records to keep: as-built route drawings, splice schedules, OTDR traces (both directions), power meter results, closure coordinates and test dates.

Handover documentation must match the installed fibre numbers and tray assignments; an outdated splice schedule causes wrong-fibre cuts during later repairs.

A work order should state scope, cable and fibre IDs, test limits, material list, and completion date; a signed completion report triggers payment.

Quotation for a splicing job = labour (splices × rate) + materials (closures, sleeves, patch cords) + testing + travel + applicable GST.

A splice rate per fibre and a separate rate per closure is a common pricing model; testing and OTDR reports are billed as separate line items.

Customer communication: confirm the appointment, explain the downtime window, and state the expected restoration time before starting work.

Basic record keeping: invoice number, date, work order reference, materials consumed, test results and customer signature, kept for tax and warranty.

A technician's personal protective equipment, calibrated test gear and valid training certificates are the main evidence of professional competence.

Team roles on a site: supervisor for permits and safety, splicer for joint work, helper for cable handling, and tester for OTDR and power meter records.

Small-business compliance in Punjab: GST registration above the turnover threshold, Udyam registration for MSME benefits, and a current electrical licence for powered work.