Fiber Chromatic Dispersion Penalty and Reach
Computes accumulated chromatic dispersion, source pulse spread, bit period.
Example
You enter
- Dispersion coefficient (ps/nm/km) 17
- Fiber span (km) 80
- Bit rate (Gb/s) 10
- Source spectral width (nm) 0.1
- Lower comparison rate (Gb/s) 2.5
- Higher comparison rate (Gb/s) 40
You get
- Accumulated dispersion 1,360.0 ps/nm
- Dispersion-limited reach 58.8 km
- Reach at lower rate 941.2 km
- Reach at higher rate 3.7 km
- Span status OVER the planning limit by 36.0 %
Checked against published worked examples from: Texas A&M University (S. Palermo, ECEN 689 Optical Interconnects).
Details, formula, and sources
ScopeComputes accumulated chromatic dispersion, source pulse spread, bit period, and the NRZ planning reach 100,000/(D x B^2). Reach falls with the square of bit rate: an 80 km standard-fiber span is within a 2.5 Gb/s planning limit but beyond the roughly 59 km limit at 10 Gb/s. This is separate from optical loss; transceiver tolerance and cable data govern.
Formula or tableaccumulated dispersion = D L; pulse spread = D L delta-lambda; bit period = 1/B; externally modulated NRZ planning reach is approximately 100,000/(D B^2) km for D in ps/nm/km and B in Gb/s.
Source and editionChromatic-dispersion accumulation and an externally modulated NRZ reach rule of thumb, not a transceiver guarantee.
Free accessProducts, a reciprocal, and a square-law planning relation.
What governsEstimate. AHJ and licensed professional govern.
API field namesdispersion_ps_nm_km, span_km, bit_rate_gbps, spectral_width_nm, lower_bit_rate_gbps, higher_bit_rate_gbps, accumulated_dispersion_ps_nm, reach_km, lower_rate_reach_km, higher_rate_reach_km, over_limit_pct
- NRZ planning rule constant and allowable penalty vary by modulation and source chirpthe transceiver specification
- Uniform dispersion one entered coefficient across the spanthe cable data at operating wavelength
- Other impairments excluded PMD, nonlinear effects and attenuation are separate checksthe transmission design