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352-001 · Question #786

Which two descriptions of CWDM are true? (Choose two)

The correct answer is D. shares the same transmission window as DWDM E. Passive CWDM devices require no electrical power. CWDM's wavelength range overlaps with the DWDM transmission window in the C-band, and passive CWDM mux/demux devices use optical thin-film filters that require no electrical power.

Designing Network Infrastructure

Question

Which two descriptions of CWDM are true? (Choose two)

Options

  • Atypically used over long distances, but requires optical amplification
  • Buses the 850nm band
  • Callows up to 32 optical earners to be multiplexed onto a single fiber
  • Dshares the same transmission window as DWDM
  • EPassive CWDM devices require no electrical power

How the community answered

(24 responses)
  • B
    4% (1)
  • C
    4% (1)
  • D
    92% (22)

Why each option

CWDM's wavelength range overlaps with the DWDM transmission window in the C-band, and passive CWDM mux/demux devices use optical thin-film filters that require no electrical power.

Atypically used over long distances, but requires optical amplification

CWDM is designed for short to medium distances (typically up to 80km) and does not require optical amplification; it is DWDM that is used over long-haul distances and requires EDFA amplifiers.

Buses the 850nm band

CWDM operates in the 1270nm to 1610nm range; the 850nm band is used by short-reach multimode fiber transceivers (such as 1000BASE-SX), which are unrelated to CWDM.

Callows up to 32 optical earners to be multiplexed onto a single fiber

CWDM supports a maximum of 18 channels with 20nm channel spacing; it is DWDM that achieves 32, 80, or more channels using much tighter 0.8nm or 0.4nm spacing.

Dshares the same transmission window as DWDMCorrect

CWDM spans 1270nm to 1610nm per ITU-T G.694.2, which includes the C-band (1530-1565nm) used by DWDM, meaning both technologies operate within the same optical transmission window in that region.

EPassive CWDM devices require no electrical powerCorrect

Passive CWDM multiplexer and demultiplexer devices use thin-film filter or prism technology to separate wavelengths purely optically, requiring zero electrical power to function.

Concept tested: CWDM channel capacity and passive device characteristics

Source: https://www.cisco.com/c/en/us/products/collateral/interfaces-modules/cwdm-gbic-modules/prod_white_paper0900aecd804cd07e.html

Topics

#CWDM#optical networking#WDM#passive devices

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