Calculators for free-space optical communication links.
26 calculators
Fried parameter r₀, Greenwood frequency, isoplanatic angle and Strehl ratio with and without adaptive optics for a free-space optical link.
Weak-fluctuation aperture-averaging factor for plane and spherical waves (exact integrals for a hard circular or Gaussian aperture, and Andrews' fits), Rytov variance and the all-regime scintillation index versus receiver diameter.
RMS turbulence-induced wander of a collimated Gaussian beam, its angular jitter and the mean on-axis loss versus Cn², path length and beam radius.
Bit and symbol error rates of BPSK, Gray-coded QPSK and OQPSK versus Eb/N0, with spectral efficiency, bandwidth, and the shot-noise-limited coherent receive power and margin.
Required fade margin and diversity gain of selection, equal-gain and maximal-ratio combining with N receivers, from the irradiance correlation at their separation in weak turbulence.
Optical attenuation in fog from visibility with the Kim, Kruse or Al Naboulsi (advection, radiation fog) model: specific attenuation in dB/km, path loss and transmittance.
Stare acquisition probability, raster scan lines and time over the 3σ uncertainty cone, beacon margin and the quadrant-detector tracking error for a free-space optical terminal.
Visibility-based aerosol (Kim) and Rayleigh scattering: attenuation in dB/km, total path loss and transmittance of a free-space optical link.
Background power, photon rate and photoelectrons per bit from clear sky, clouds or the Sun for a given field of view, aperture, filter passband and wavelength (850–1550 nm).
Shannon capacity and the net rate of OOK, BPSK, QPSK, 8-PSK and 16-QAM after hard-decision FEC, gated on their exact AWGN bit error rates, with the required SNR and the gap to Shannon.
NOHD, IEC 60825-1 laser class and exposure margin at a chosen distance for a free-space optical transmitter, on the ICNIRP 2013 eye limits with a diverging Gaussian beam.
Gamma-gamma and log-normal fade probability versus fade threshold for an FSO link in turbulence, with aperture averaging and N uncorrelated receivers.
Geometric spreading loss of a divergent FSO beam: top-hat footprint from exit aperture and divergence versus the exact Gaussian-beam capture by the receiver aperture.
Free-space optical link budget from transmitter divergence, receiver aperture, path loss and atmospheric attenuation per km, with the margin against receiver sensitivity versus range.
Power that the receiver and an off-axis eavesdropper collect from a Gaussian beam, their SNRs and the wiretap secrecy capacity for a free-space optical link.
Compare 850, 1064, 1310 and 1550 nm for an FSO link by Class 1 eye-safety limit, atmospheric loss over the range, component maturity and cost, and get a weighted recommendation.
Lasercom link budget with Gaussian-beam transmit and receive gains, free-space path loss, spot size at the receiver, and pointing and atmospheric losses.
Telescope transmit gain (Klein–Degnan, clipped and obscured Gaussian beam), receive gain, far-field divergence, beam waist and Rayleigh range, with beam quality M² up to 10 as a Gaussian Schell-model beam.
Exact Poisson bit error rate of photon-counting OOK and DPSK receivers versus detected photons per bit and dark plus background counts.
Point-ahead angle 2v⊥/c from the transverse relative velocity, compared with the diffraction half-angle, with the miss distance and light time for LEO and GEO laser links.
Interactive free-space optical pointing-loss calculator with jitter, misalignment, and aperture coupling.
Decoy-state BB84 secure key rate (GLLP), QBER, single-photon gain, maximum distance and optimal mean photon number versus channel loss, with the PLOB repeaterless bound.
Specific and path attenuation of a free-space optical link in rain with the ITU-R P.1814-1 model: γ = k·R^α for a gamma drop-size distribution, path reduction factor and multiple-scattering gain.
Electrical SNR of a PIN or APD receiver versus field of view, with background light from clear sky, clouds or the Sun, the signal clipped by the field stop (diffraction and turbulence), and the FOV at which background noise overtakes amplifier noise.
Rytov variance, aperture averaging, and fade probability for atmospheric turbulence.
Specific and total attenuation of a free-space optical link in dry or wet snow from the water-equivalent snowfall rate and wavelength, with the Koschmieder-equivalent visibility.