CodingBox دستاویزات

DWDM سسٹم کے اجزاء

ہماری ٹیم ترجمے پر کام کر رہی ہے۔ یہ مضمون عارضی طور پر اردو میں دستیاب نہیں ہے، اس لیے اسے انگریزی میں دکھایا جا رہا ہے۔

Unlike CWDM, a DWDM link is a system: coloured transmitters, precise filters, amplifiers and often dispersion management, all engineered together. Knowing the parts tells you what a pluggable DWDM transceiver is plugging into.

Where the coloured light comes from

ApproachWhat it isWhere used
Pluggable DWDM transceivera coloured SFP+/QSFP28/QSFP-DD in the router or switch itself"IP over DWDM", metro, DCI
Transpondera shelf card: grey client optic in, DWDM line optic outclassic transport systems
Muxpondera transponder that aggregates several clients (e.g. 10×10G) into one 100G+ wavelengthtransport, backbone

Pluggable DWDM optics — fixed or tunable — remove the transponder, which is why coding and tuning them from the host side matters.

Multiplexing

  • Mux/demux — thermally stabilised AWG (arrayed waveguide grating) or thin-film filters on the ITU grid, 40/48/96 channels; insertion loss ~4–7 dB.
  • OADM / ROADM — fixed or reconfigurable add/drop; a ROADM uses a wavelength- selective switch (WSS) so channels can be routed by software.
  • Interleaver — combines two 100 GHz grids offset by 50 GHz into one 50 GHz grid.

Amplification

DWDM's defining advantage is that all C-band channels can be amplified together by an EDFA (erbium-doped fibre amplifier):

AmplifierPositionRole
Booster (BA)after the muxraises launch power
In-line (LA)mid-span, every ~80–120 kmovercomes span loss
Pre-amplifier (PA)before the demuximproves receiver sensitivity

Each EDFA adds ~20–30 dB of gain and some noise; the accumulated noise sets the OSNR that ultimately limits reach (coherent & long-haul). Raman amplification (distributed, in the transmission fibre) extends spans further. L-band amplifiers double capacity on the same fibre.

Dispersion management

  • DCM (dispersion-compensating module) — a spool of DCF or a fibre Bragg grating that cancels chromatic dispersion for direct-detect 10G links beyond ~80 km.
  • EDC — electronic compensation inside a 10G module (limited).
  • Coherent — 100G+ receivers compensate dispersion digitally; no DCM needed.

Supervision

An optical supervisory channel (OSC) on a wavelength outside the amplified band (e.g. 1510 nm) carries management between amplifier sites. Optical channel monitors read per-channel power at the mux.

In CodingBox

Where the coloured source is a pluggable, CodingBox is the tool that touches it: it reads the module's channel/wavelength, its power and DDM, sets the channel on tunable modules through SFF-8690 / SFF-TA-1004, and codes identity for the host platform.

Amplifiers as infrastructure — types and numbers, placement on the line, the OSNR budget, operating rules and the choice against regeneration: Amplifiers & regeneration; transponders, ROADMs and protection switches as equipment classes: Transport & access equipment.

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