This simulator models a point-to-point fiber-optic link — a transmit SFP driving a laser through connectors, fusion splices and a length of fiber into a receive SFP photodiode — and calculates the optical power budget end to end. Adjust launch power, route length, fiber attenuation, connector pairs, splice count, bend loss, receiver sensitivity and overload threshold, then send test frames and watch whether received power lands inside the receiver's usable window.
• A real-time 3D cutaway workbench of the transmit SFP, LC connector and ferrule, a magnified fiber core/cladding cross-section, a fusion splice enclosure, a bend/service-loop fixture and the receive SFP/photodiode, with home view, focus-selected-part, toggleable full-enclosure view, exploded view, auto-rotate and expand controls, tappable numbered components with callouts, and labels matching a companion diagram. • Twelve live controls: transmitter launch power, fiber route length, fiber attenuation coefficient, number of connector pairs, loss per connector pair, number of fusion splices, loss per splice, additional bend loss, receiver sensitivity, receiver overload threshold, periodic test-traffic toggle and traffic interval. • Play/pause, single-step (0.1 s) and larger-step (1 s) time controls, plus a playback-speed selector (10x slow motion, real time, 10x faster, 1 minute per second). • Start trial, stop trial and send test traffic actions, with a live "what is happening" sequence narrative and per-component operating status. • Six live metrics: total path attenuation, receiver sensitivity margin, received optical power in dBm, received optical power in µW, test frames sent and frames delivered within the receiver's power window. • A Curves & measurements tab with a received-power-over-time chart, an attenuation/margin chart, the full model equations and snapshot measurements. • An Experiments tab with four guided scenarios (nominal 10 km link, excessive route loss, bend degradation, receiver overload from too much launch power), an automated model-verification bench of independent checks, and a timestamped event log with a copyable trial report. • A Learn & assess tab with four guided lessons, a two-question knowledge-check quiz and a written scope/reference statement.
The model sums every loss source along the path: fiber attenuation scales with route length and the attenuation coefficient (dB/km), each connector pair and fusion splice adds its configured per-unit loss, and an additional bend-loss term represents excess loss from a service loop or tight bend radius. Received power is simply launch power minus this total loss, expressed in dBm — a logarithmic unit of absolute optical power referenced to 1 mW.
A link is only usable if received power clears two separate limits: it must exceed the receiver's sensitivity (the minimum power the photodiode can reliably detect) and it must stay below the receiver's overload threshold (the maximum input the receiver can tolerate without saturating). The margin metric reports the gap above sensitivity, but a comfortably positive margin says nothing about the overload limit — the receiver-overload experiment is built specifically to show a case where margin looks healthy while the link still fails.
The equations panel gives L = α × km + Nconnector × Lconnector + Nsplice × Lsplice + Lbend for total loss, Prx(dBm) = Ptx − L for received power, Margin = Prx − sensitivity, Power(µW) = 1000 × 10^(Prx/10) for the linear-power readout, and a propagation-time estimate of 5 µs/km. Test frames are marked delivered only when received power falls inside the sensitivity-to-overload window.
This is a representative power-budget and binary receiver-window model, not a full optical-link solver: it excludes chromatic and modal dispersion, wavelength-dependent behavior, laser safety classification, bit-error-rate calculation, eye-diagram analysis and any real modulation scheme. All traffic, timing and fault injection are simulated locally, and equipment geometry — especially the enlarged fiber cross-section — is illustrative rather than a manufacturer CAD model.
A receiver has two separate limits: a minimum sensitivity and a maximum overload threshold. Margin only measures the gap above sensitivity. The receiver-overload experiment sets a short, low-loss link with high launch power specifically to show that a large positive sensitivity margin does not prevent the received power from exceeding the overload limit and causing frames to fail.
The model sums fiber attenuation (attenuation coefficient × route length in km), the number of connector pairs times loss per pair, the number of fusion splices times loss per splice, and a separate additional bend-loss term for excess loss from bending or a service loop. The total is L = α×km + Nconnector×Lconnector + Nsplice×Lsplice + Lbend, and received power is launch power minus L.
dBm is a logarithmic measure of absolute optical power referenced to 1 milliwatt. The simulator also reports the equivalent linear power using Power(µW) = 1000 × 10^(Prx/10), so you can see the same received power expressed both logarithmically and linearly.
It is a representative power-budget and binary pass/fail receiver-window model. It does not model chromatic or modal dispersion, wavelength-specific attenuation, laser safety classification, bit-error rate, eye diagrams or an actual modulation/demodulation scheme, and the enlarged fiber cross-section is illustrative rather than a real manufacturer geometry. All traffic is simulated offline.