WDM Channel Plan

WDM channel wavelengths, frequency spacing, ITU-T grid type (CWDM or DWDM), total bandwidth, insertion loss and Gaussian-passband isolation from channel count and spacing.

Model: Illustrative

Number of Channels

Channel Spacing (nm)

Center Wavelength (nm)

Passband Width (nm)

Insertion Loss (dB)

Channel Plan

Ch 1:1547.21 nm

Ch 2:1548.00 nm

Ch 3:1548.80 nm

Ch 4:1549.60 nm

Ch 5:1550.40 nm

Ch 6:1551.20 nm

Ch 7:1552.00 nm

Ch 8:1552.81 nm

Results

Grid type:ITU-T G.694.1 DWDM, 100 GHz

Frequency spacing:99.8 GHz

Total bandwidth:5.6 nm

Insertion loss:0.5 dB

Adjacent-channel isolation (Gaussian passbands):48.2 dB

Formulas

Δf = c·Δλ / λ²

BW_total = λ_max − λ_min (≈ (N − 1)·Δλ)

ISO = 10·log₁₀(e)·4 ln2·(Δλ/FWHM)² ≈ 12.04·(Δλ/FWHM)² dB

DWDM plans (G.694.1) are spaced equally in frequency, CWDM (G.694.2) in wavelength. Gaussian passbands are illustrative (thin-film filters are flat-topped with steeper skirts, Mach–Zehnder interleavers sin²). G.694.1 anchors channels at 193.1 THz + kΔν, so enter a grid frequency's wavelength as the centre for an on-grid plan.

Model and references

Illustrative. A simplified model that shows trends and orders of magnitude. Don't use its numbers for design. About the tiers

Channel plan on equal frequency steps for the G.694.1 DWDM spacings (Δν = cΔλ/λ² at the centre) and equal wavelength steps otherwise (G.694.2 CWDM). Gaussian passbands give the adjacent-channel isolation 12.04(Δλ/FWHM)² dB; real filters (flat-top thin film, sin² interleavers) differ. Not modelled: anchoring to 193.1 THz.

ITU-T G.694.1. Spectral grids for WDM applications: DWDM frequency grid.
ITU-T G.694.2. Spectral grids for WDM applications: CWDM wavelength grid (20 nm, 1271–1611 nm).

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