Non-Zero Dispersion Shifted Fiber (NZ-DSF)
Design NZ-DSF fibers (G.655) with optimized dispersion for DWDM systems — balancing dispersion and nonlinearity.
D(λ) NZ-DSF
4.50 ps/nm/km
λ₀ = 1460 nm
Accumulated D·L
360 ps/nm
Channel Spacing Δλ
0.801 nm
FWM Δβ = 2.243 rad/km
SMF (G.652) at this λ
17.5 ps/nm/km
|D| 3.9× the NZ-DSF value
Chromatic Dispersion vs Wavelength
Accumulated Dispersion vs Distance
Key Formulas
D(λ) = D(1550) + S · (λ − 1550 nm), λ₀ = 1550 nm − D(1550)/S
G.652 reference: D(λ) = (S₀/4)(λ − λ₀⁴/λ³), S₀ = 0.092, λ₀ = 1310 nm
Δλ = λ² · Δν / c
Δβ_FWM = −(2πΔν)²[β₂ + β₃·2πΔν], β₂ = −λ²D/(2πc), β₃ = (λ²/2πc)²(S + 2D/λ)
G.655.C: 1 ≤ |D| ≤ 10 ps/(nm·km) and D_max − D_min ≤ 5 over 1530–1565 nm (Table 1)
Trade-off: low |D| → stronger FWM; high |D| → more compensation needed
Model and references
Textbook approximation. A standard approximation from the literature (for example paraxial, plane-wave or Gaussian-beam), valid within the range the page states. About the tiers
Linear D(λ) about 1550 nm from your D and slope, compared with G.652 (Sellmeier) and G.653 presets; valid over 1460–1625 nm, so λ0 is shown only inside that band. FWM phase mismatch with β₂ and β₃ from D and S.
- ITU-T G.655. Characteristics of a non-zero dispersion-shifted single-mode optical fibre and cable (G.655.C: 1 ≤ |D| ≤ 10 ps/(nm·km) over 1530–1565 nm). itu.int
- ITU-T G.652 (11/2016). Characteristics of a single-mode optical fibre and cable. D(λ) = (S₀/4)(λ − λ₀⁴/λ³) with 1300 ≤ λ₀ ≤ 1324 nm and S₀ ≤ 0.092 ps/(nm²·km). itu.int
- Agrawal G. P. (2010). Fiber-Optic Communication Systems, 4th ed., §2.3 (β₂). Wiley. doi:10.1002/9780470918524