Punjab PSEB Matric NSQF Telecom (Optical Fiber Splicer) flashcards

34 cards. Read the term and the definition here. The deck at the top of this page is optional.

Critical angle

The minimum incidence angle at which light in the core is totally internally reflected at the core-cladding boundary; it exists only when the core index exceeds the cladding index.

Numerical aperture

NA = sqrt(n1 squared minus n2 squared). It sets the acceptance cone of the fibre, so a higher NA couples more light but supports more modes.

V-number

V = (2 pi a / lambda) times NA. When V is below about 2.405 the fibre supports only the fundamental mode and behaves as single-mode at that wavelength.

Decibel formula

Attenuation in decibels equals ten times the base-10 logarithm of input power divided by output power; loss per kilometre is that value divided by fibre length.

TIA-598 12-fibre colour code

Blue, orange, green, brown, slate, white, red, black, yellow, violet, rose, aqua. The same sequence numbers buffer tubes and repeats with tracers beyond twelve.

Single-mode jacket colour

Yellow jacket marks single-mode OS1 or OS2 cable with a 9 micrometre core, used at 1310 and 1550 nanometres for long distances.

Multimode jacket colours

Orange marks OM1 and OM2, aqua marks OM3 and OM4, and lime green marks OM5; all are used with 850 nanometre sources over short reaches.

Loose-tube versus tight-buffer

Loose-tube cable houses fibres in gel-filled tubes for outdoor duct and aerial routes; tight-buffered cable places coating directly on the fibre for indoor riser and patch use.

Cleaver end-face quality

An acceptable cleave has an angle of 0.5 degrees or less with no hackle, lip or mist; the splicer end-face viewer confirms it before arc fusion.

Visual fault locator use

A red laser injected into the fibre glows at breaks, tight bends and damaged connectors within a few kilometres, giving a quick location before OTDR testing.

Mandrel wrap live-fibre check

Five turns of fibre around a 25 or 30 millimetre mandrel strip enough light at 1310 and 1550 nanometres for a power meter to confirm the fibre is not live.

Connector inspection scope

A 200x or 400x magnifier used to inspect connector end faces for dust, scratches and residue before mating, preventing permanent damage and high loss.

Coating strip length

Bare glass of roughly 30 to 40 millimetres is exposed, then cleaved to the splicer's specified bare-fibre length, commonly 8 to 16 millimetres.

Buffer tube gel cleaning

Gel is wiped from exposed fibres with lint-free wipes and 99 percent isopropyl alcohol; dry tissue alone leaves residue that causes bubbles and high splice loss.

Fibre scrap handling

Bare glass offcuts go into a rigid sealed scrap container immediately, never on the floor or clothing, because splinters are nearly invisible and penetrate skin.

Arc calibration check

An arc check is run before each splicing session and after electrode changes, altitude or humidity shifts, because arc power drifts and affects splice quality.

Good fusion splice loss

A single-mode fusion splice should measure about 0.05 decibels or less; a splicer estimate above roughly 0.1 decibels is rejected and re-spliced.

Mechanical splice loss

A mechanical splice aligns cleaved fibres in a precision sleeve with index-matching gel and typically gives 0.1 to 0.3 decibels, useful where no power is available.

Splice protector placement

The heat-shrink protector with its steel strength rod is centred over the bare fibre and fully shrunk in the oven, then cooled before loading into the tray.

Bidirectional OTDR testing

Splice loss is measured from both ends and averaged, because differing backscatter coefficients on the two fibres make single-direction readings inaccurate.

OTDR dead zone

The event dead zone is about one metre and the attenuation dead zone about four metres; launch and receive fibres are added to resolve short links.

Power meter reference method

The reference is set with the same connectors, launch cords and wavelength as the link under test, then the link is inserted and loss read directly.

Test wavelengths

Single-mode links are tested at 1310 and 1550 nanometres, multimode at 850 and 1300 nanometres, and a link must pass at every specified wavelength.

Closure IP68 rating

IP68 means dust-tight and protected against water immersion under stated conditions, required for buried and manhole splice closures exposed to standing water.

Splice tray bend radius

Fibres inside a splice tray and closure must be routed at a minimum bend radius of about 30 millimetres to avoid macrobending loss and long-term damage.

Closure earthing bond

The cable's metallic strength member and armour are clamped and bonded to earth through the closure, keeping the screen continuous across the joint.

GPON downstream rates

GPON carries 2.488 gigabits per second downstream at 1490 nanometres and 1.244 gigabits per second upstream at 1310 nanometres over a passive split tree.

Splitter loss rule

Splitter loss is about ten times the base-10 logarithm of the split ratio plus excess loss, so a 1:32 splitter contributes roughly 16.5 decibels.

ONT ranging

The OLT measures each ONT's round-trip delay and assigns an equalisation delay so all upstream bursts arrive aligned in their granted time slots.

Optical power budget

Total loss of fibre attenuation, splices, connectors and splitters must stay below the class budget, about 28 decibels for class B+ GPON.

Invisible laser hazard

1310 and 1550 nanometre light is invisible and focuses on the retina; never view a fibre end or connector directly, and use only filtered indirect scopes.

Manhole gas testing

Before entry, test for oxygen, combustible gas, hydrogen sulphide and carbon monoxide, then ventilate continuously with a standby person and harness at the surface.

Splice schedule record

A document listing closure ID, cable IDs, fibre numbers spliced, tray assignment and measured loss, which must match the as-built records at handover.

Splicing quotation basis

Price equals splices times rate plus materials, testing and travel, with applicable tax; testing and OTDR reports are quoted as separate line items.