Fiber & telecom

Estimate Gaussian beam to single-mode fiber coupling efficiency from beam waist, fiber MFD, and alignment offsets.

Synthesize a 200G-per-lane PAM4 waveform with adjustable bandwidth, noise, jitter, extinction ratio, and level skew, and compute TDECQ through the Bessel-Thomson reference receiver and a 5-tap equalizer, with equalized histograms, tap weights, and guided experiments.

Loss-margin waterfall, per-lane G.652 chromatic dispersion with UI-spread zones, and energy per bit across pluggable, LPO, and CPO at fleet scale, with presets for 400G, 800G, and 1.6T classes and guided experiments.

Which noise source limits a PIN or avalanche photodiode receiver, and what is the weakest signal it can see: signal shot, dark-current shot, thermal and amplifier noise summed over the bandwidth into SNR, noise-equivalent power, minimum detectable power, the shot-noise crossover power and the optimum APD gain, with the shot-noise limit, noise and SNR plots, guided experiments and a validation table.

Chromatic dispersion of single-mode fiber from D and slope or from the zero-dispersion wavelength with the ITU-T G.652 formula: β₂ and β₃, dispersion length, broadening and compression of a chirped Gaussian pulse, accumulated dispersion, compensating-fiber length and residual slope, the dispersion-limited bit rate and length, fiber presets, and a 15-row validation table.

Optical power between dBm, mW, W and dBW; gain and loss as dB, linear and field ratios, percent and optical density; wavelength to frequency, photon energy and wavenumber; and linewidth between Δν, Δλ and Δσ, with photon flux, ideal responsivity, telecom band, nearest DWDM channel, coherence length and a validation table.

OSNR at the end of a chain of amplified spans from launch power, span loss, noise figure, span count and reference bandwidth, with per-amplifier ASE, margin over a required OSNR and the longest chain that meets it, plus the Friis gain and noise figure of up to five amplifiers and losses, with plots, presets, guided experiments and a validation table.

ITU-T G.694.1 DWDM channel frequencies and wavelengths on the fixed and flexible grids for any band, with the channel count, spacing in wavelength, the nearest channel to a wavelength, a full channel table and the CWDM wavelengths.

Numerical aperture and acceptance angle of an optical fiber from its core and cladding indices, the V number, single-mode or multimode guidance and the guided LP modes, the cutoff wavelength, and the mode field diameter by Marcuse's formula, with an acceptance-cone diagram, V and MFD against wavelength, presets, guided experiments and a validation table.

One-way and round-trip delay of a fiber link from its length and group index, the data in flight, the saving from hollow-core fiber, the comparison with a straight line at the speed of light, the length an OTDR reports with a given index setting and the dispersion skew between two wavelengths, with a delay plot, presets, guided experiments and a validation table.

The quiet foundation of much of photonics: the fiber that spans oceans at 0.2 dB/km, the cladding of silicon and nitride waveguides, and a common substrate for free-space optics.